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Android 4.2 兼容性定義

修訂版 2
最後更新：2013 年 2 月 17 日

一、簡介

本文檔列舉了設備與 Android 4.2 兼容必須滿足的要求。

“必須”、“不得”、“要求”、“應”、“不應”、“應該”、“不應”、“推薦”、“可能”和“可選”的使用符合 IETF 標準在 RFC2119 [資源，1 ] 中定義。

本文檔中使用的“設備實施者”或“實施者”是指開發運行 Android 4.2 的硬件/軟件解決方案的個人或組織。 “設備實現”或“實現”是這樣開發的硬件/軟件解決方案。

要被視為與 Android 4.2 兼容，設備實現必須滿足本兼容性定義中提出的要求，包括通過引用併入的任何文檔。

如果此定義或第 10 節中描述的軟件測試是沉默的、模棱兩可的或不完整的，則設備實現者有責任確保與現有實現的兼容性。

出於這個原因，Android 開源項目 [ Resources, 3 ] 既是 Android 的參考實現，也是首選實現。強烈建議設備實施者盡可能將其實施基於 Android 開源項目提供的“上游”源代碼。雖然假設某些組件可以替換為替代實現，但強烈建議不要這樣做，因為通過軟件測試將變得更加困難。實施者有責任確保與標準 Android 實施的行為完全兼容，包括和超越兼容性測試套件。最後，請注意，本文檔明確禁止某些組件替換和修改。

2. 資源

IETF RFC2119 要求級別： http ://www.ietf.org/rfc/rfc2119.txt

Android 兼容性計劃概述：http: //source.android.com/compatibility/index.html

Android 開源項目：http: //source.android.com/

API 定義和文檔：http: //developer.android.com/reference/packages.html

Android 權限參考：http: //developer.android.com/reference/android/Manifest.permission.html

android.os.Build 參考：http: //developer.android.com/reference/android/os/Build.html

Android 4.2 允許的版本字符串：http: //source.android.com/compatibility/4.2/versions.html

渲染腳本：http: //developer.android.com/guide/topics/graphics/renderscript.html

硬件加速：http: //developer.android.com/guide/topics/graphics/hardware-accel.html

android.webkit.WebView 類：http: //developer.android.com/reference/android/webkit/WebView.html

HTML5：http: //www.whatwg.org/specs/web-apps/current-work/multipage/

HTML5 離線功能： http ://dev.w3.org/html5/spec/Overview.html#offline

HTML5 視頻標籤： http ://dev.w3.org/html5/spec/Overview.html#video

HTML5/W3C 地理定位 API： http ://www.w3.org/TR/geolocation-API/

HTML5/W3C 網絡數據庫 API： http ://www.w3.org/TR/webdatabase/

HTML5/W3C IndexedDB API： http ://www.w3.org/TR/IndexedDB/

Dalvik 虛擬機規範：可在 Android 源代碼中找到，位於 dalvik/docs

AppWidgets：http: //developer.android.com/guide/practices/ui_guidelines/widget_design.html

通知：http: //developer.android.com/guide/topics/ui/notifiers/notifications.html

應用資源： http ://code.google.com/android/reference/available-resources.html

狀態欄圖標樣式指南：http: //developer.android.com/guide/practices/ui_guidelines/icon_design_status_bar.html

搜索管理器：http: //developer.android.com/reference/android/app/SearchManager.html

祝酒詞：http: //developer.android.com/reference/android/widget/Toast.html

主題：http: //developer.android.com/guide/topics/ui/themes.html

R.style 類：http: //developer.android.com/reference/android/R.style.html

動態壁紙：http: //developer.android.com/resources/articles/live-wallpapers.html

Android 設備管理：http: //developer.android.com/guide/topics/admin/device-admin.html

DevicePolicyManager 參考：http: //developer.android.com/reference/android/app/admin/DevicePolicyManager.html

Android 無障礙服務 API：http: //developer.android.com/reference/android/accessibilityservice/package-summary.html

Android 無障礙 API：http: //developer.android.com/reference/android/view/accessibility/package-summary.html

眼睛免費項目： http ://code.google.com/p/eyes-free

文字轉語音 API：http: //developer.android.com/reference/android/speech/tts/package-summary.html

參考工具文檔（用於 adb、aapt、ddms、systrace）：http: //developer.android.com/guide/developing/tools/index.html

Android apk 文件說明：http: //developer.android.com/guide/topics/fundamentals.html

清單文件：http: //developer.android.com/guide/topics/manifest/manifest-intro.html

猴子測試工具：http: //developer.android.com/guide/developing/tools/monkey.html

Android android.content.pm.PackageManager 類和硬件特性列表：http: //developer.android.com/reference/android/content/pm/PackageManager.html

支持多屏：http: //developer.android.com/guide/practices/screens_support.html

android.util.DisplayMetrics：http: //developer.android.com/reference/android/util/DisplayMetrics.html

android.content.res.Configuration：http: //developer.android.com/reference/android/content/res/Configuration.html

android.hardware.SensorEvent：http: //developer.android.com/reference/android/hardware/SensorEvent.html

藍牙 API：http: //developer.android.com/reference/android/bluetooth/package-summary.html

NDEF 推送協議：http: //source.android.com/compatibility/ndef-push-protocol.pdf

MIFARE MF1S503X： http ://www.nxp.com/documents/data_sheet/MF1S503x.pdf

MIFARE MF1S703X： http ://www.nxp.com/documents/data_sheet/MF1S703x.pdf

MIFARE MF0ICU1： http ://www.nxp.com/documents/data_sheet/MF0ICU1.pdf

MIFARE MF0ICU2： http ://www.nxp.com/documents/short_data_sheet/MF0ICU2_SDS.pdf

MIFARE AN130511： http ://www.nxp.com/documents/application_note/AN130511.pdf

MIFARE AN130411： http ://www.nxp.com/documents/application_note/AN130411.pdf

相機方向 API：http: //developer.android.com/reference/android/hardware/Camera.html#setDisplayOrientation(int)

相機：http: //developer.android.com/reference/android/hardware/Camera.html

Android 打開附件：http: //developer.android.com/guide/topics/usb/accessory.html

USB 主機 API：http: //developer.android.com/guide/topics/usb/host.html

Android 安全和權限參考：http: //developer.android.com/guide/topics/security/security.html

適用於 Android 的應用程序： http ://code.google.com/p/apps-for-android

安卓下載管理器：http: //developer.android.com/reference/android/app/DownloadManager.html

安卓文件傳輸： http ://www.android.com/filetransfer

Android 媒體格式：http: //developer.android.com/guide/appendix/media-formats.html

HTTP 直播流協議草案： http ://tools.ietf.org/html/draft-pantos-http-live-streaming-03

NFC 連接切換： http ://www.nfc-forum.org/specs/spec_list/#conn_handover

使用 NFC 的藍牙安全簡單配對： http ://www.nfc-forum.org/resources/AppDocs/NFCForum_AD_BTSSP_1_0.pdf

Wifi 多播 API：http: //developer.android.com/reference/android/net/wifi/WifiManager.MulticastLock.html

動作輔助：http: //developer.android.com/reference/android/content/Intent.html#ACTION_ASSIST

USB 充電規範： http ://www.usb.org/developers/devclass_docs/USB_Battery_Charging_1.2.pdf

Android Beam：http: //developer.android.com/guide/topics/nfc/nfc.html

Android USB 音頻：http: //developer.android.com/reference/android/hardware/usb/UsbConstants.html#USB_CLASS_AUDIO

Android NFC 共享設置：http: //developer.android.com/reference/android/provider/Settings.html#ACTION_NFCSHARING_SETTINGS

Wifi 直連（Wifi P2P）：http: //developer.android.com/reference/android/net/wifi/p2p/WifiP2pManager.html

鎖定和主屏幕小部件：http: //developer.android.com/reference/android/appwidget/AppWidgetProviderInfo.html

用戶管理器參考：http: //developer.android.com/reference/android/os/UserManager.html

外部存儲參考：http: //source.android.com/tech/storage

外部存儲 API：http: //developer.android.com/reference/android/os/Environment.html

短信短代碼： http ://en.wikipedia.org/wiki/Short_code

媒體遠程控制客戶端：http: //developer.android.com/reference/android/media/RemoteControlClient.html

顯示管理器：http: //developer.android.com/reference/android/hardware/display/DisplayManager.html

夢想：http: //developer.android.com/reference/android/service/dreams/DreamService.html

Android 應用程序開發相關設置：http: //developer.android.com/reference/android/provider/Settings.html#ACTION_APPLICATION_DEVELOPMENT_SETTINGS

相機：http: //developer.android.com/reference/android/hardware/Camera.Parameters.html

其中許多資源直接或間接源自 Android 4.2 SDK，並且在功能上與該 SDK 文檔中的信息相同。在此兼容性定義或兼容性測試套件與 SDK 文檔不一致的任何情況下，SDK 文檔被視為權威。上述參考文獻中提供的任何技術細節都被視為包含在本兼容性定義中。

3. 軟件

3.1。託管 API 兼容性

託管（基於 Dalvik）的執行環境是 Android 應用程序的主要工具。 Android 應用程序編程接口 (API) 是向在託管 VM 環境中運行的應用程序公開的一組 Android 平台接口。設備實現必須提供 Android 4.2 SDK [資源， 4 ] 公開的任何文檔化 API 的完整實現，包括所有文檔化行為。

設備實現不得省略任何託管 API、更改 API 接口或簽名、偏離記錄的行為或包含無操作，除非此兼容性定義特別允許。

此兼容性定義允許設備實現忽略 Android 包含 API 的某些類型的硬件。在這種情況下，API 必須仍然存在並以合理的方式運行。有關此場景的具體要求，請參見第 7 節。

3.2.軟 API 兼容性

除了第 3.1 節中的託管 API 之外，Android 還包括一個重要的僅運行時“軟”API，其形式為諸如 Intent、權限和 Android 應用程序的類似方面等無法在應用程序編譯時強制執行的方面。

3.2.1。權限

設備實現者必須支持並強制執行權限參考頁 [資源，5 ] 中記錄的所有權限常量。請注意，第 10 節列出了與 Android 安全模型相關的其他要求。

3.2.2.構建參數

Android API 在android.os.Build類 [ Resources, 6 ] 上包含許多常量，用於描述當前設備。為了在設備實現中提供一致、有意義的值，下表包含了對設備實現必須遵守的這些值的格式的額外限制。

範圍	註釋
android.os.Build.VERSION.RELEASE	當前執行的 Android 系統的版本，採用人類可讀的格式。該字段必須具有 [ Resources, 7 ] 中定義的字符串值之一。
android.os.Build.VERSION.SDK	當前執行的 Android 系統的版本，採用第三方應用程序代碼可訪問的格式。對於 Android 4.2，此字段必須具有整數值 17。
android.os.Build.VERSION.SDK_INT	當前執行的 Android 系統的版本，採用第三方應用程序代碼可訪問的格式。對於 Android 4.2，此字段必須具有整數值 17。
android.os.Build.VERSION.INCREMENTAL	設備實現者選擇的值，以人類可讀的格式指定當前執行的 Android 系統的特定構建。此值不得重新用於最終用戶可用的不同構建。此字段的典型用途是指示使用哪個構建號或源代碼控制更改標識符來生成構建。該字段的具體格式沒有要求，但不能為空或空字符串（“”）。
android.os.Build.BOARD	設備實現者選擇的一個值，用於標識設備使用的特定內部硬件，採用人類可讀的格式。該字段的一個可能用途是指示為設備供電的電路板的特定版本。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.BRAND	由設備實施者選擇的值，以人類可讀的格式標識生產設備的公司、組織、個人等的名稱。此字段的一種可能用途是指明銷售設備的 OEM 和/或運營商。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.CPU_ABI	本機代碼的指令集名稱（CPU 類型 + ABI 約定）。請參閱第 3.3 節：本機 API 兼容性。
android.os.Build.CPU_ABI2	本機代碼的第二個指令集（CPU 類型 + ABI 約定）的名稱。請參閱第 3.3 節：本機 API 兼容性。
android.os.Build.DEVICE	由設備實施者選擇的一個值，用於標識設備主體的特定配置或修訂（有時稱為“工業設計”）。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.FINGERPRINT	唯一標識此構建的字符串。它應該是合理的人類可讀的。它必須遵循這個模板： `$(BRAND)/$(PRODUCT)/$(DEVICE):$(VERSION.RELEASE)/$(ID)/$(VERSION.INCREMENTAL):$(TYPE)/$(TAGS)` 例如： `acme/mydevice/generic:4.2/JRN53/3359:userdebug/test-keys` 指紋不得包含空格字符。如果上面模板中包含的其他字段包含空格字符，則必須在構建指紋中將它們替換為另一個字符，例如下劃線（“_”）字符。該字段的值必須可編碼為 7 位 ASCII。
android.os.Build.HARDWARE	硬件的名稱（來自內核命令行或 /proc）。它應該是合理的人類可讀的。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.HOST	一個字符串，以人類可讀的格式唯一標識構建所基於的主機。該字段的具體格式沒有要求，但不能為空或空字符串（“”）。
android.os.Build.ID	設備實現者選擇的標識符，用於引用特定版本，採用人類可讀的格式。此字段可以與 android.os.Build.VERSION.INCREMENTAL 相同，但應該是一個足以讓最終用戶區分軟件構建的值。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.MANUFACTURER	產品的原始設備製造商 (OEM) 的商品名稱。該字段的具體格式沒有要求，但不能為空或空字符串（“”）。
android.os.Build.MODEL	由設備實現者選擇的一個值，其中包含最終用戶已知的設備名稱。這應該與設備銷售和銷售給最終用戶的名稱相同。該字段的具體格式沒有要求，但不能為空或空字符串（“”）。
android.os.Build.PRODUCT	由設備實施者選擇的一個值，其中包含產品的開發名稱或代碼名稱 (SKU)。必須是人類可讀的，但不一定供最終用戶查看。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.SERIAL	硬件序列號（如果有）。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^([a-zA-Z0-9]{0,20})$"` 。
android.os.Build.TAGS	由設備實現者選擇的以逗號分隔的標籤列表，用於進一步區分構建。例如，“未簽名，調試”。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.TIME	表示構建發生時間的時間戳的值。
android.os.Build.TYPE	設備實現者選擇的值，指定構建的運行時配置。該字段應該具有對應於三個典型 Android 運行時配置的值之一：“user”、“userdebug”或“eng”。此字段的值必須可編碼為 7 位 ASCII 並匹配正則表達式`"^[a-zA-Z0-9.,_-]+$"` 。
android.os.Build.USER	生成構建的用戶（或自動用戶）的名稱或用戶 ID。該字段的具體格式沒有要求，但不能為空或空字符串（“”）。

3.2.3。意圖兼容性

設備實現必須遵循 Android 的鬆散耦合 Intent 系統，如下節所述。 “尊敬”是指設備實現者必須提供一個 Android 活動或服務，該活動或服務指定一個匹配的 Intent 過濾器，並綁定到每個指定的 Intent 模式並實現正確的行為。

3.2.3.1。核心應用意圖

Android 上游項目定義了一些核心應用，如聯繫人、日曆、相冊、音樂播放器等。設備實施者可以用替代版本替換這些應用程序。

但是，任何此類替代版本都必須遵循上游項目提供的相同 Intent 模式。例如，如果設備包含替代音樂播放器，它仍必須遵循第三方應用程序發布的 Intent 模式來挑選歌曲。

以下應用程序被視為核心 Android 系統應用程序：

台鐘
瀏覽器
日曆
聯繫人
畫廊
全球搜索
啟動器
音樂
設置

核心 Android 系統應用程序包括各種被視為“公共”的 Activity 或 Service 組件。也就是說，屬性“android:exported”可能不存在，或者可能具有值“true”。

對於在核心 Android 系統應用之一中定義的每個 Activity 或 Service 未通過值為“false”的 android:exported 屬性標記為非公共，設備實現必須包含實現相同 Intent 過濾器的相同類型的組件模式作為核心的Android系統應用程序。

換句話說，設備實現可能會取代核心的 Android 系統應用程序；但是，如果支持，設備實現必須支持每個被替換的核心 Android 系統應用程序定義的所有 Intent 模式。

3.2.3.2。意圖覆蓋

由於 Android 是一個可擴展的平台，設備實現必須允許第 3.2.3.2 節中引用的每個 Intent 模式被第三方應用程序覆蓋。上游 Android 開源實現默認允許這樣做；設備實現者不得將特殊權限附加到系統應用程序對這些 Intent 模式的使用，或阻止第三方應用程序綁定並控制這些模式。該禁止具體包括但不限於禁用“選擇器”用戶界面，該界面允許用戶在所有處理相同意圖模式的多個應用程序之間進行選擇。

但是，如果默認活動為數據 URI 提供更具體的過濾器，則設備實現可以為特定 URI 模式（例如 http://play.google.com）提供默認活動。例如，指定數據 URI“http://www.android.com”的意圖過濾器比“http://”的瀏覽器過濾器更具體。設備實現必須為用戶提供一個用戶界面來修改意圖的默認活動。

3.2.3.3。意圖命名空間

設備實現不得包含任何使用 android.* 或 com.android.* 命名空間中的 ACTION、CATEGORY 或其他鍵字符串來支持任何新 Intent 或 Broadcast Intent 模式的 Android 組件。設備實施者不得在屬於另一個組織的包空間中包含任何使用 ACTION、CATEGORY 或其他鍵字符串來尊重任何新 Intent 或 Broadcast Intent 模式的 Android 組件。設備實現者不得更改或擴展第 3.2.3.1 節中列出的核心應用程序使用的任何 Intent 模式。設備實現可能包括使用名稱空間的 Intent 模式，這些名稱空間與它們自己的組織相關聯。

這種禁止類似於第 3.6 節中為 Java 語言類指定的禁止。

3.2.3.4。廣播意圖

第三方應用程序依靠平台廣播某些 Intent 來通知他們硬件或軟件環境的變化。 Android 兼容設備必須廣播公共廣播 Intent 以響應適當的系統事件。廣播意圖在 SDK 文檔中進行了描述。

3.3.原生 API 兼容性

3.3.1 應用二進制接口

在 Dalvik 中運行的託管代碼可以調用應用程序 .apk 文件中提供的本機代碼，作為為適當的設備硬件架構編譯的 ELF .so 文件。由於本機代碼高度依賴於底層處理器技術，Android 在文件docs/CPU-ARCH-ABIS.html中的 Android NDK 中定義了許多應用程序二進制接口 (ABI)。如果設備實現與一個或多個定義的 ABI 兼容，它應該實現與 Android NDK 的兼容性，如下所示。

如果設備實現包括對 Android ABI 的支持，它：

必須包括對在託管環境中運行的代碼的支持，以使用標準 Java 本機接口 (JNI) 語義調用本機代碼。
必須與以下列表中的每個所需庫兼容源代碼（即標頭兼容）和二進制兼容（對於 ABI）
必須通過android.os.Build.CPU_ABI API 準確報告設備支持的本機應用程序二進制接口 (ABI)
必須僅在文件docs/CPU-ARCH-ABIS.txt中報告最新版本的 Android NDK 中記錄的 ABI
應該使用上游 Android 開源項目中可用的源代碼和頭文件構建

以下本機代碼 API 必須可用於包含本機代碼的應用程序：

libc（C 庫）
libm（數學庫）
對 C++ 的最低支持
JNI接口
liblog（Android 日誌記錄）
libz（Zlib 壓縮）
libdl（動態鏈接器）
libGLESv1_CM.so (OpenGL ES 1.0)
libGLESv2.so (OpenGL ES 2.0)
libEGL.so（原生 OpenGL 表面管理）
libjnigraphics.so
libOpenSLES.so（OpenSL ES 1.0.1 音頻支持）
libOpenMAXAL.so（OpenMAX AL 1.0.1 支持）
libandroid.so（原生 Android 活動支持）
支持 OpenGL，如下所述

請注意，Android NDK 的未來版本可能會引入對其他 ABI 的支持。如果設備實現與現有的預定義 ABI 不兼容，則它絕不能報告對任何 ABI 的支持。

本機代碼兼容性具有挑戰性。出於這個原因，應該重申的是，強烈鼓勵設備實現者使用上面列出的庫的上游實現，以幫助確保兼容性。

3.4.網絡兼容性

3.4.1。 Web 視圖兼容性

Android 開源實現使用 WebKit 渲染引擎來實現android.webkit.WebView 。因為為 Web 渲染系統開發一個全面的測試套件是不可行的，設備實現者必須在 WebView 實現中使用特定的上游構建的 WebKit。具體來說：

設備實現的android.webkit.WebView實現必須基於來自 Android 4.2 的上游 Android 開源樹的 534.30 WebKit 構建。此版本包括一組特定的 WebView 功能和安全修復程序。設備實現者可以包括對 WebKit 實現的定制；但是，任何此類自定義都不得改變 WebView 的行為，包括呈現行為。
WebView 報告的用戶代理字符串必須採用以下格式：
Mozilla/5.0 (Linux; U; Android $(VERSION); $(LOCALE); $(MODEL) Build/$(BUILD)) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.2 Mobile Safari/534.30
- $(VERSION) 字符串的值必須與android.os.Build.VERSION.RELEASE的值相同
- $(LOCALE) 字符串的值應該遵循國家代碼和語言的 ISO 約定，並且應該參考設備當前配置的區域設置
- $(MODEL) 字符串的值必須與android.os.Build.MODEL的值相同
- $(BUILD) 字符串的值必須與android.os.Build.ID的值相同
- 設備實現可以在用戶代理字符串中省略Mobile

WebView 組件應該盡可能多地支持 HTML5 [參考資料，11 ]。最低限度，設備實現必須支持與 WebView 中的 HTML5 關聯的這些 API：

應用程序緩存/離線操作 [資源，12 ]
<video> 標籤 [資源，13 ]
地理位置 [資源, 14 ]

此外，設備實現必須支持 HTML5/W3C webstorage API [資源，15 ]，並且應該支持 HTML5/W3C IndexedDB API [資源，16 ]。請注意，隨著 Web 開發標準機構正在轉變為偏愛 IndexedDB 而不是 webstorage，IndexedDB 有望成為未來版本 Android 的必需組件。

HTML5 API 與所有 JavaScript API 一樣，必須在 WebView 中默認禁用，除非開發人員通過通常的 Android API 明確啟用它們。

3.4.2.瀏覽器兼容性

設備實現必須包含用於一般用戶網頁瀏覽的獨立瀏覽器應用程序。獨立瀏覽器可能基於 WebKit 以外的瀏覽器技術。但是，即使使用備用瀏覽器應用程序，提供給第三方應用程序的android.webkit.WebView組件也必須基於 WebKit，如第 3.4.1 節所述。

實現可以在獨立的瀏覽器應用程序中提供自定義用戶代理字符串。

獨立的瀏覽器應用程序（無論是基於上游 WebKit 瀏覽器應用程序還是第三方替代品）應該盡可能多地支持 HTML5 [參考資料，11 ]。最低限度，設備實現必須支持與 HTML5 相關的這些 API：

應用程序緩存/離線操作 [資源，12 ]
<video> 標籤 [資源，13 ]
地理位置 [資源, 14 ]

3.5. API 行為兼容性

每種 API 類型（託管、軟、原生和 Web）的行為必須與上游 Android 開源項目 [參考資料，3 ] 的首選實現一致。一些特定的兼容性領域是：

設備不得更改標準 Intent 的行為或語義
設備不得改變特定類型的系統組件（如服務、活動、內容提供者等）的生命週期或生命週期語義
設備不得更改標準權限的語義

上面的列表並不全面。兼容性測試套件 (CTS) 測試平台的重要部分的行為兼容性，但不是全部。實施者有責任確保與 Android 開源項目的行為兼容性。出於這個原因，設備實現者應該盡可能使用通過 Android 開源項目提供的源代碼，而不是重新實現系統的重要部分。

3.6. API 命名空間

Android 遵循 Java 編程語言定義的包和類命名空間約定。為確保與第三方應用程序的兼容性，設備實施者不得對這些包命名空間進行任何禁止的修改（見下文）：

爪哇。*
javax.*
太陽。*
安卓。*
com.android.*

禁止的修改包括：

設備實現不得通過更改任何方法或類簽名或刪除類或類字段來修改 Android 平台上公開的 API。
設備實現者可以修改 API 的底層實現，但此類修改不得影響任何公開公開的 API 的聲明行為和 Java 語言簽名。
設備實現者不得將任何公開暴露的元素（例如類或接口，或現有類或接口的字段或方法）添加到上述 API。

A "publicly exposed element" is any construct which is not decorated with the "@hide" marker as used in the upstream Android source code. In other words, device implementers MUST NOT expose new APIs or alter existing APIs in the namespaces noted above. Device implementers MAY make internal-only modifications, but those modifications MUST NOT be advertised or otherwise exposed to developers.

Device implementers MAY add custom APIs, but any such APIs MUST NOT be in a namespace owned by or referring to another organization. For instance, device implementers MUST NOT add APIs to the com.google.* or similar namespace; only Google may do so. Similarly, Google MUST NOT add APIs to other companies' namespaces. Additionally, if a device implementation includes custom APIs outside the standard Android namespace, those APIs MUST be packaged in an Android shared library so that only apps that explicitly use them (via the <uses-library> mechanism) are affected by the increased memory usage of such APIs.

If a device implementer proposes to improve one of the package namespaces above (such as by adding useful new functionality to an existing API, or adding a new API), the implementer SHOULD visit source.android.com and begin the process for contributing changes and code, according to the information on that site.

Note that the restrictions above correspond to standard conventions for naming APIs in the Java programming language; this section simply aims to reinforce those conventions and make them binding through inclusion in this compatibility definition.

3.7. Virtual Machine Compatibility

Device implementations MUST support the full Dalvik Executable (DEX) bytecode specification and Dalvik Virtual Machine semantics [ Resources, 17 ].

Device implementations MUST configure Dalvik to allocate memory in accordance with the upstream Android platform, and as specified by the following table. (See Section 7.1.1 for screen size and screen density definitions.)

Note that memory values specified below are considered minimum values, and device implementations MAY allocate more memory per application.

Screen Size	Screen Density	Application Memory
small / normal / large	ldpi / mdpi	16MB
small / normal / large	tvdpi / hdpi	32MB
small / normal / large	xhdpi	64MB
xlarge	mdpi	32MB
xlarge	tvdpi / hdpi	64MB
xlarge	xhdpi	128MB

3.8. User Interface Compatibility

3.8.1. Widgets

Android defines a component type and corresponding API and lifecycle that allows applications to expose an "AppWidget" to the end user [ Resources, 18 ]. The Android Open Source reference release includes a Launcher application that includes user interface affordances allowing the user to add, view, and remove AppWidgets from the home screen.

Device implementations MAY substitute an alternative to the reference Launcher (ie home screen). Alternative Launchers SHOULD include built-in support for AppWidgets, and expose user interface affordances to add, configure, view, and remove AppWidgets directly within the Launcher. Alternative Launchers MAY omit these user interface elements; however, if they are omitted, the device implementation MUST provide a separate application accessible from the Launcher that allows users to add, configure, view, and remove AppWidgets.

Device implementations MUST be capable of rendering widgets that are 4 x 4 in the standard grid size. (See the App Widget Design Guidelines in the Android SDK documentation [ Resources, 18 ] for details.

3.8.2. Notifications

Android includes APIs that allow developers to notify users of notable events [ Resources, 19 ], using hardware and software features of the device.

Some APIs allow applications to perform notifications or attract attention using hardware, specifically sound, vibration, and light. Device implementations MUST support notifications that use hardware features, as described in the SDK documentation, and to the extent possible with the device implementation hardware. For instance, if a device implementation includes a vibrator, it MUST correctly implement the vibration APIs. If a device implementation lacks hardware, the corresponding APIs MUST be implemented as no-ops. Note that this behavior is further detailed in Section 7.

Additionally, the implementation MUST correctly render all resources (icons, sound files, etc.) provided for in the APIs [ Resources, 20 ], or in the Status/System Bar icon style guide [ Resources, 21 ]. Device implementers MAY provide an alternative user experience for notifications than that provided by the reference Android Open Source implementation; however, such alternative notification systems MUST support existing notification resources, as above.

Android 4.2 includes support for rich notifications, such as interactive Views for ongoing notifications. Device implementations MUST properly display and execute rich notifications, as documented in the Android APIs.

3.8.3. Search

Android includes APIs [ Resources, 22 ] that allow developers to incorporate search into their applications, and expose their application's data into the global system search. Generally speaking, this functionality consists of a single, system-wide user interface that allows users to enter queries, displays suggestions as users type, and displays results. The Android APIs allow developers to reuse this interface to provide search within their own apps, and allow developers to supply results to the common global search user interface.

Device implementations MUST include a single, shared, system-wide search user interface capable of real-time suggestions in response to user input. Device implementations MUST implement the APIs that allow developers to reuse this user interface to provide search within their own applications. Device implementations MUST implement the APIs that allow third-party applications to add suggestions to the search box when it is run in global search mode. If no third-party applications are installed that make use of this functionality, the default behavior SHOULD be to display web search engine results and suggestions.

3.8.4. Toasts

Applications can use the "Toast" API (defined in [ Resources, 23 ]) to display short non-modal strings to the end user, that disappear after a brief period of time. Device implementations MUST display Toasts from applications to end users in some high-visibility manner.

3.8.5. Themes

Android provides "themes" as a mechanism for applications to apply styles across an entire Activity or application. Android 4.2 includes a "Holo" or "holographic" theme as a set of defined styles for application developers to use if they want to match the Holo theme look and feel as defined by the Android SDK [ Resources, 24 ]. Device implementations MUST NOT alter any of the Holo theme attributes exposed to applications [ Resources, 25 ].

Android 4.2 includes a new "Device Default" theme as a set of defined styles for application developers to use if they want to match the look and feel of the device theme as defined by the device implementer. Device implementations MAY modify the DeviceDefault theme attributes exposed to applications [ Resources, 25 ].

3.8.6. Live Wallpapers

Android defines a component type and corresponding API and lifecycle that allows applications to expose one or more "Live Wallpapers" to the end user [ Resources, 26 ]. Live Wallpapers are animations, patterns, or similar images with limited input capabilities that display as a wallpaper, behind other applications.

Hardware is considered capable of reliably running live wallpapers if it can run all live wallpapers, with no limitations on functionality, at a reasonable framerate with no adverse affects on other applications. If limitations in the hardware cause wallpapers and/or applications to crash, malfunction, consume excessive CPU or battery power, or run at unacceptably low frame rates, the hardware is considered incapable of running live wallpaper. As an example, some live wallpapers may use an Open GL 1.0 or 2.0 context to render their content. Live wallpaper will not run reliably on hardware that does not support multiple OpenGL contexts because the live wallpaper use of an OpenGL context may conflict with other applications that also use an OpenGL context.

Device implementations capable of running live wallpapers reliably as described above SHOULD implement live wallpapers. Device implementations determined to not run live wallpapers reliably as described above MUST NOT implement live wallpapers.

3.8.7. Recent Application Display

The upstream Android 4.2 source code includes a user interface for displaying recent applications using a thumbnail image of the application's graphical state at the moment the user last left the application. Device implementations MAY alter or eliminate this user interface; however, a future version of Android is planned to make more extensive use of this functionality. Device implementations are strongly encouraged to use the upstream Android 4.2 user interface (or a similar thumbnail-based interface) for recent applications, or else they may not be compatible with a future version of Android.

3.8.8. Input Management Settings

Android 4.2 includes support for Input Management Engines. The Android 4.2 APIs allow custom app IMEs to specify user-tunable settings. Device implementations MUST include a way for the user to access IME settings at all times when an IME that provides such user settings is displayed.

3.8.9. Lock and Home Screen Widgets

Android 4.2 includes support for application widgets that users can embed in the home screen or the lock screen (See the App Widget Design Guidelines in the Android SDK documentation [ Resources, 69 ] for details). Application widgets allow quick access to application data and services without launching a new activity. Widgets declare support for usage on the home screen or the lock screen by declaring the android:widgetCategory manifest tag that tells the system where the widget can be placed. Specifically, device implementations MUST meet the following requirements.

Device implementations MUST support application widgets on the home screen.
Device implementations SHOULD support lock screen. If device implementations include support for lock screen then device implementations MUST support application widgets on the lock screen.

3.8.10. Lock Screen Media Remote Control

Android 4.2 includes support for Remote Control API that lets media applications integrate with playback controls that are displayed in a remote view like the device lock screen[ Resources, 74 ]. Device implementations MUST include support for embedding remote controls in the device lock screen.

3.8.11. Dreams

Android 4.2 includes support for interactive screensavers called Dreams [ Resources, 76 ]. Dreams allows users to interact with applications when a charging device is idle, or docked in a desk dock. Device implementations MUST include support for Dreams and provide a settings option for users to configure Dreams.

3.9 Device Administration

Android 4.2 includes features that allow security-aware applications to perform device administration functions at the system level, such as enforcing password policies or performing remote wipe, through the Android Device Administration API [ Resources, 27 ]. Device implementations MUST provide an implementation of the DevicePolicyManager class [ Resources, 28 ], and SHOULD support the full range of device administration policies defined in the Android SDK documentation [ Resources, 27 ].

Note: while some of the requirements outlined above are stated as "SHOULD" for Android 4.2, device implementations that support lock screen MUST support device policies to manage widgets on the lock screen as defined in the Android SDK documentation [ Resources, 27 ].

Note: while some of the requirements outlined above are stated as "SHOULD" for Android 4.2, the Compatibility Definition for a future version is planned to change these to "MUST". That is, these requirements are optional in Android 4.2 but will be required by a future version. Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 , or they will not be able to attain Android compatibility when upgraded to the future version.

3.10 Accessibility

Android 4.2 provides an accessibility layer that helps users with disabilities to navigate their devices more easily. In addition, Android 4.2 provides platform APIs that enable accessibility service implementations to receive callbacks for user and system events and generate alternate feedback mechanisms, such as text-to-speech, haptic feedback, and trackball/d-pad navigation [ Resources, 29 ]. Device implementations MUST provide an implementation of the Android accessibility framework consistent with the default Android implementation. Specifically, device implementations MUST meet the following requirements.

Device implementations MUST support third party accessibility service implementations through the android.accessibilityservice APIs [ Resources, 30 ].
Device implementations MUST generate AccessibilityEvents and deliver these events to all registered AccessibilityService implementations in a manner consistent with the default Android implementation.
Device implementations MUST provide a user-accessible mechanism to enable and disable accessibility services, and MUST display this interface in response to the android.provider.Settings.ACTION_ACCESSIBILITY_SETTINGS intent.

Additionally, device implementations SHOULD provide an implementation of an accessibility service on the device, and SHOULD provide a mechanism for users to enable the accessibility service during device setup. An open source implementation of an accessibility service is available from the Eyes Free project [ Resources, 31 ].

3.11 Text-to-Speech

Android 4.2 includes APIs that allow applications to make use of text-to-speech (TTS) services, and allows service providers to provide implementations of TTS services [ Resources, 32 ]. Device implementations MUST meet these requirements related to the Android TTS framework:

Device implementations MUST support the Android TTS framework APIs and SHOULD include a TTS engine supporting the languages available on the device. Note that the upstream Android open source software includes a full-featured TTS engine implementation.
Device implementations MUST support installation of third-party TTS engines.
Device implementations MUST provide a user-accessible interface that allows users to select a TTS engine for use at the system level.

4. Application Packaging Compatibility

Device implementations MUST install and run Android ".apk" files as generated by the "aapt" tool included in the official Android SDK [ Resources, 33 ].

Devices implementations MUST NOT extend either the .apk [ Resources, 34 ], Android Manifest [ Resources, 35 ], Dalvik bytecode [ Resources, 17 ], or renderscript bytecode formats in such a way that would prevent those files from installing and running correctly on other compatible devices. Device implementers SHOULD use the reference upstream implementation of Dalvik, and the reference implementation's package management system.

5. Multimedia Compatibility

Device implementations MUST include at least one form of audio output, such as speakers, headphone jack, external speaker connection, etc.

5.1. Media Codecs

Device implementations MUST support the core media formats specified in the Android SDK documentation [ Resources, 58 ] except where explicitly permitted in this document. Specifically, device implementations MUST support the media formats, encoders, decoders, file types and container formats defined in the tables below. All of these codecs are provided as software implementations in the preferred Android implementation from the Android Open Source Project.

Please note that neither Google nor the Open Handset Alliance make any representation that these codecs are unencumbered by third-party patents. Those intending to use this source code in hardware or software products are advised that implementations of this code, including in open source software or shareware, may require patent licenses from the relevant patent holders.

Note that these tables do not list specific bitrate requirements for most video codecs because current device hardware does not necessarily support bitrates that map exactly to the required bitrates specified by the relevant standards. Instead, device implementations SHOULD support the highest bitrate practical on the hardware, up to the limits defined by the specifications.

類型	Format / Codec	Encoder	Decoder	Details	File Type(s) / Container Formats
聲音的	MPEG-4 AAC Profile (AAC LC)	REQUIRED Required for device implementations that include microphone hardware and define `android.hardware.microphone` .	REQUIRED	Support for mono/stereo/5.0/5.1* content with standard sampling rates from 8 to 48 kHz.	3GPP (.3gp) MPEG-4 (.mp4, .m4a) ADTS raw AAC (.aac, decode in Android 3.1+, encode in Android 4.0+, ADIF not supported) MPEG-TS (.ts, not seekable, Android 3.0+)
	MPEG-4 HE AAC Profile (AAC+)	REQUIRED for device implementations that include microphone hardware and define android.hardware.microphone	REQUIRED	Support for mono/stereo/5.0/5.1* content with standard sampling rates from 16 to 48 kHz.
	MPEG-4 HE AAC v2 Profile (enhanced AAC+)		REQUIRED	Support for mono/stereo/5.0/5.1* content with standard sampling rates from 16 to 48 kHz.
	MPEG-4 Audio Object Type ER AAC ELD (Enhanced Low Delay AAC)	REQUIRED for device implementations that include microphone hardware and define android.hardware.microphone	REQUIRED	Support for mono/stereo content with standard sampling rates from 16 to 48 kHz.
	AMR-NB	REQUIRED Required for device implementations that include microphone hardware and define `android.hardware.microphone` .	REQUIRED	4.75 to 12.2 kbps sampled @ 8kHz	3GPP (.3gp)
	AMR-WB	REQUIRED Required for device implementations that include microphone hardware and define `android.hardware.microphone` .	REQUIRED	9 rates from 6.60 kbit/s to 23.85 kbit/s sampled @ 16kHz	3GPP (.3gp)
	FLAC		REQUIRED (Android 3.1+)	Mono/Stereo (no multichannel). Sample rates up to 48 kHz (but up to 44.1 kHz is recommended on devices with 44.1 kHz output, as the 48 to 44.1 kHz downsampler does not include a low-pass filter). 16-bit recommended; no dither applied for 24-bit.	FLAC (.flac) only
	MP3		REQUIRED	Mono/Stereo 8-320Kbps constant (CBR) or variable bit-rate (VBR)	MP3 (.mp3)
	MIDI		REQUIRED	MIDI Type 0 and 1. DLS Version 1 and 2. XMF and Mobile XMF. Support for ringtone formats RTTTL/RTX, OTA, and iMelody	Type 0 and 1 (.mid, .xmf, .mxmf) RTTTL/RTX (.rtttl, .rtx) OTA (.ota) iMelody (.imy)
	Vorbis		REQUIRED		Ogg (.ogg) Matroska (.mkv)
	PCM/WAVE	REQUIRED	REQUIRED	8-bit and 16-bit linear PCM** (rates up to limit of hardware).Devices MUST support sampling rates for raw PCM recording at 8000,16000 and 44100 Hz frequencies	WAVE (.wav)
Image	JPEG	REQUIRED	REQUIRED	Base+progressive	JPEG (.jpg)
	GIF		REQUIRED		GIF (.gif)
	PNG	REQUIRED	REQUIRED		PNG (.png)
	BMP		REQUIRED		BMP (.bmp)
	WEBP	REQUIRED	REQUIRED		WebP (.webp)
視頻	H.263	REQUIRED Required for device implementations that include camera hardware and define `android.hardware.camera` or `android.hardware.camera.front` .	REQUIRED		3GPP (.3gp) MPEG-4 (.mp4)
	H.264 AVC	REQUIRED Required for device implementations that include camera hardware and define `android.hardware.camera` or `android.hardware.camera.front` .	REQUIRED	Baseline Profile (BP)	3GPP (.3gp) MPEG-4 (.mp4) MPEG-TS (.ts, AAC audio only, not seekable, Android 3.0+)
	MPEG-4 SP		REQUIRED		3GPP (.3gp)
	VP8		REQUIRED (Android 2.3.3+)		WebM (.webm) and Matroska (.mkv, Android 4.0+)

*Note: Only downmix of 5.0/5.1 content is required; recording or rendering more than 2 channels is optional. **Note: 16-bit linear PCM capture is mandatory. 8-bit linear PCM capture is not mandatory.

5.2 Video Encoding

Android device implementations that include a rear-facing camera and declare android.hardware.camera SHOULD support the following video encoding profiles.

	SD (Low quality)	SD (High quality)	HD (When supported by hardware)
Video codec	H.264 Baseline Profile	H.264 Baseline Profile	H.264 Baseline Profile
Video resolution	176 x 144 px	480 x 360 px	1280 x 720 px
Video frame rate	12 fps	30 fps	30 fps
Video bitrate	56 Kbps	500 Kbps or higher	2 Mbps or higher
Audio codec	AAC-LC	AAC-LC	AAC-LC
Audio channels	1 (mono)	2 (stereo)	2 (stereo)
Audio bitrate	24 Kbps	128 Kbps	192 Kbps

5.3 Video Decoding

Android device implementations SHOULD support the following VP8 video decoding profiles.

	SD (Low quality)	SD (High quality)	HD 720p (When supported by hardware)	HD 1080p (When supported by hardware)
Video resolution	320 x 180 px	640 x 360 px	1280 x 720 px	1920 x 1080 px
Video frame rate	30 fps	30 fps	30 fps	30 fps
Video bitrate	800 Kbps	2 Mbps	8 Mbps	20 Mbps

5.4. Audio Recording

When an application has used the android.media.AudioRecord API to start recording an audio stream, device implementations that include microphone hardware and declare android.hardware.microphone MUST sample and record audio with each of these behaviors:

The device SHOULD exhibit approximately flat amplitude versus frequency characteristics; specifically, ±3 dB, from 100 Hz to 4000 Hz
Audio input sensitivity SHOULD be set such that a 90 dB sound power level (SPL) source at 1000 Hz yields RMS of 2500 for 16-bit samples.
PCM amplitude levels SHOULD linearly track input SPL changes over at least a 30 dB range from -18 dB to +12 dB re 90 dB SPL at the microphone.
Total harmonic distortion SHOULD be less than 1% for 1Khz at 90 dB SPL input level.

In addition to the above recording specifications, when an application has started recording an audio stream using the android.media.MediaRecorder.AudioSource.VOICE_RECOGNITION audio source:

Noise reduction processing, if present, MUST be disabled.
Automatic gain control, if present, MUST be disabled.

5.5. Audio Latency

Audio latency is the time delay as an audio signal passes through a system. Many classes of applications rely on short latencies, to achieve real-time effects such sound effects or VOIP communication.

For the purposes of this section:

"output latency" is defined as the interval between when an application writes a frame of PCM-coded data and when the corresponding sound can be heard by an external listener or observed by a transducer
"cold output latency" is defined as the output latency for the first frame, when the audio output system has been idle and powered down prior to the request
"continuous output latency" is defined as the output latency for subsequent frames, after the device is already playing audio
"input latency" is the interval between when an external sound is presented to the device and when an application reads the corresponding frame of PCM-coded data
"cold input latency" is defined as the sum of lost input time and the input latency for the first frame, when the audio input system has been idle and powered down prior to the request
"continuous input latency" is defined as the input latency for subsequent frames, while the device is already capturing audio
"OpenSL ES PCM buffer queue API" is the set of PCM-related OpenSL ES APIs within Android NDK; see NDK_root /docs/opensles/index.html

Per Section 5 , all compatible device implementations MUST include at least one form of audio output. Device implementations SHOULD meet or exceed these output latency requirements:

cold output latency of 100 milliseconds or less
continuous output latency of 45 milliseconds or less

If a device implementation meets the requirements of this section after any initial calibration when using the OpenSL ES PCM buffer queue API, for continuous output latency and cold output latency over at least one supported audio output device, it MAY report support for low-latency audio, by reporting the feature "android.hardware.audio.low-latency" via the android.content.pm.PackageManager class. [ Resources, 37 ] Conversely, if the device implementation does not meet these requirements it MUST NOT report support for low-latency audio.

Per Section 7.2.5 , microphone hardware may be omitted by device implementations.

Device implementations that include microphone hardware and declare android.hardware.microphone SHOULD meet these input audio latency requirements:

cold input latency of 100 milliseconds or less
continuous input latency of 50 milliseconds or less

5.6. Network Protocols

Devices MUST support the media network protocols for audio and video playback as specified in the Android SDK documentation [ Resources, 58 ]. Specifically, devices MUST support the following media network protocols:

RTSP (RTP, SDP)
HTTP(S) progressive streaming
HTTP(S) Live Streaming draft protocol, Version 3 [ Resources, 59 ]

6. Developer Tools and Options Compatibility

6.1 Developer Tools

Device implementations MUST support the Android Developer Tools provided in the Android SDK. Specifically, Android-compatible devices MUST be compatible with:

Android Debug Bridge (known as adb) [ Resources, 33 ]
Device implementations MUST support all adb functions as documented in the Android SDK. The device-side adb daemon MUST be inactive by default, and there MUST be a user-accessible mechanism to turn on the Android Debug Bridge.

Android 4.2.2 includes support for secure adb. Secure adb enables adb on known authenticated hosts. Existing and new devices that run Android 4.2.2 are very strongly encouraged to meet this requirement in Android 4.2 , or they will not be able to attain Android compatibility when upgraded to the future version.

Dalvik Debug Monitor Service (known as ddms) [ Resources, 33 ]
Device implementations MUST support all ddms features as documented in the Android SDK. As ddms uses adb , support for ddms SHOULD be inactive by default, but MUST be supported whenever the user has activated the Android Debug Bridge, as above.
Monkey [ Resources, 36 ]
Device implementations MUST include the Monkey framework, and make it available for applications to use.
SysTrace [ Resources, 33 ]
Device implementations MUST support systrace tool as documented in the Android SDK. Systrace must be inactive by default, and there MUST be a user-accessible mechanism to turn on Systrace.

Most Linux-based systems and Apple Macintosh systems recognize Android devices using the standard Android SDK tools, without additional support; however Microsoft Windows systems typically require a driver for new Android devices. (For instance, new vendor IDs and sometimes new device IDs require custom USB drivers for Windows systems.) If a device implementation is unrecognized by the adb tool as provided in the standard Android SDK, device implementers MUST provide Windows drivers allowing developers to connect to the device using the adb protocol. These drivers MUST be provided for Windows XP, Windows Vista, Windows 7, and Windows 8, in both 32-bit and 64-bit versions.

6.2 Developer Options

Android 4.2 includes support for developers to configure application development-related settings. Device implementations MUST honor the android.settings.APPLICATION_DEVELOPMENT_SETTINGS intent to show application development-related settings [ Resources, 77 ]. The upstream Android implementation hides the Developer Options menu by default, and enables users to launch Developer Options after pressing seven (7) times on the Settings > About Device > Build Number menu item. Device implementations MUST provide a consistent experience for Developer Options. Specifically, device implementations MUST hide Developer Options by default and MUST provide a mechanism to enable Developer Options that is consistent with the upstream Android implementation.

7. Hardware Compatibility

If a device includes a particular hardware component that has a corresponding API for third-party developers, the device implementation MUST implement that API as described in the Android SDK documentation. If an API in the SDK interacts with a hardware component that is stated to be optional and the device implementation does not possess that component:

complete class definitions (as documented by the SDK) for the component's APIs MUST still be present
the API's behaviors MUST be implemented as no-ops in some reasonable fashion
API methods MUST return null values where permitted by the SDK documentation
API methods MUST return no-op implementations of classes where null values are not permitted by the SDK documentation
API methods MUST NOT throw exceptions not documented by the SDK documentation

A typical example of a scenario where these requirements apply is the telephony API: even on non-phone devices, these APIs must be implemented as reasonable no-ops.

Device implementations MUST accurately report accurate hardware configuration information via the getSystemAvailableFeatures() and hasSystemFeature(String) methods on the android.content.pm.PackageManager class. [ Resources, 37 ]

7.1. Display and Graphics

Android 4.2 includes facilities that automatically adjust application assets and UI layouts appropriately for the device, to ensure that third-party applications run well on a variety of hardware configurations [ Resources, 38 ]. Devices MUST properly implement these APIs and behaviors, as detailed in this section.

The units referenced by the requirements in this section are defined as follows:

"Physical diagonal size" is the distance in inches between two opposing corners of the illuminated portion of the display.
"dpi" (meaning "dots per inch") is the number of pixels encompassed by a linear horizontal or vertical span of 1". Where dpi values are listed, both horizontal and vertical dpi must fall within the range.
"Aspect ratio" is the ratio of the longer dimension of the screen to the shorter dimension. For example, a display of 480x854 pixels would be 854 / 480 = 1.779, or roughly "16:9".
A "density-independent pixel" or ("dp") is the virtual pixel unit normalized to a 160 dpi screen, calculated as: pixels = dps * (density / 160) .

7.1.1. Screen Configuration

Screen Size

The Android UI framework supports a variety of different screen sizes, and allows applications to query the device screen size (aka "screen layout") via android.content.res.Configuration.screenLayout with the SCREENLAYOUT_SIZE_MASK . Device implementations MUST report the correct screen size as defined in the Android SDK documentation [ Resources, 38 ] and determined by the upstream Android platform. Specifically, device implementations must report the correct screen size according to the following logical density-independent pixel (dp) screen dimensions.

Devices MUST have screen sizes of at least 426 dp x 320 dp ('small')
Devices that report screen size 'normal' MUST have screen sizes of at least 480 dp x 320 dp
Devices that report screen size 'large' MUST have screen sizes of at least 640 dp x 480 dp
Devices that report screen size 'xlarge' MUST have screen sizes of at least 960 dp x 720 dp

In addition, devices MUST have screen sizes of at least 2.5 inches in physical diagonal size.

Devices MUST NOT change their reported screen size at any time.

Applications optionally indicate which screen sizes they support via the <supports-screens> attribute in the AndroidManifest.xml file. Device implementations MUST correctly honor applications' stated support for small, normal, large, and xlarge screens, as described in the Android SDK documentation.

Screen Aspect Ratio

The aspect ratio MUST be between 1.3333 (4:3) and 1.85 (16:9).

Screen Density

The Android UI framework defines a set of standard logical densities to help application developers target application resources. Device implementations MUST report one of the following logical Android framework densities through the android.util.DisplayMetrics APIs, and MUST execute applications at this standard density.

120 dpi, known as 'ldpi'
160 dpi, known as 'mdpi'
213 dpi, known as 'tvdpi'
240 dpi, known as 'hdpi'
320 dpi, known as 'xhdpi'
480 dpi, known as 'xxhdpi'

Device implementations SHOULD define the standard Android framework density that is numerically closest to the physical density of the screen, unless that logical density pushes the reported screen size below the minimum supported. If the standard Android framework density that is numerically closest to the physical density results in a screen size that is smaller than the smallest supported compatible screen size (320 dp width), device implementations SHOULD report the next lowest standard Android framework density.

7.1.2. Display Metrics

Device implementations MUST report correct values for all display metrics defined in android.util.DisplayMetrics [ Resources, 39 ].

7.1.3. Screen Orientation

Devices MUST support dynamic orientation by applications to either portrait or landscape screen orientation. That is, the device must respect the application's request for a specific screen orientation. Device implementations MAY select either portrait or landscape orientation as the default.

Devices MUST report the correct value for the device's current orientation, whenever queried via the android.content.res.Configuration.orientation, android.view.Display.getOrientation(), or other APIs.

Devices MUST NOT change the reported screen size or density when changing orientation.

Devices MUST report which screen orientations they support ( android.hardware.screen.portrait and/or android.hardware.screen.landscape ) and MUST report at least one supported orientation. For example, a device with a fixed-orientation landscape screen, such as a television or laptop, MUST only report android.hardware.screen.landscape .

7.1.4. 2D and 3D Graphics Acceleration

Device implementations MUST support both OpenGL ES 1.0 and 2.0, as embodied and detailed in the Android SDK documentations. Device implementations MUST also support Android Renderscript, as detailed in the Android SDK documentation [ Resources, 8 ].

Device implementations MUST also correctly identify themselves as supporting OpenGL ES 1.0 and 2.0. That is:

The managed APIs (such as via the GLES10.getString() method) MUST report support for OpenGL ES 1.0 and 2.0
The native C/C++ OpenGL APIs (that is, those available to apps via libGLES_v1CM.so, libGLES_v2.so, or libEGL.so) MUST report support for OpenGL ES 1.0 and 2.0.

Device implementations MAY implement any desired OpenGL ES extensions. However, device implementations MUST report via the OpenGL ES managed and native APIs all extension strings that they do support, and conversely MUST NOT report extension strings that they do not support.

Note that Android 4.2 includes support for applications to optionally specify that they require specific OpenGL texture compression formats. These formats are typically vendor-specific. Device implementations are not required by Android 4.2 to implement any specific texture compression format. However, they SHOULD accurately report any texture compression formats that they do support, via the getString() method in the OpenGL API.

Android 4.2 includes a mechanism for applications to declare that they wanted to enable hardware acceleration for 2D graphics at the Application, Activity, Window or View level through the use of a manifest tag android:hardwareAccelerated or direct API calls [ Resources, 9 ].

In Android 4.2, device implementations MUST enable hardware acceleration by default, and MUST disable hardware acceleration if the developer so requests by setting android:hardwareAccelerated="false" or disabling hardware acceleration directly through the Android View APIs.

In addition, device implementations MUST exhibit behavior consistent with the Android SDK documentation on hardware acceleration [ Resources, 9 ].

Android 4.2 includes a TextureView object that lets developers directly integrate hardware-accelerated OpenGL ES textures as rendering targets in a UI hierarchy. Device implementations MUST support the TextureView API, and MUST exhibit consistent behavior with the upstream Android implementation.

7.1.5. Legacy Application Compatibility Mode

Android 4.2 specifies a "compatibility mode" in which the framework operates in an 'normal' screen size equivalent (320dp width) mode for the benefit of legacy applications not developed for old versions of Android that pre-date screen-size independence. Device implementations MUST include support for legacy application compatibility mode as implemented by the upstream Android open source code. That is, device implementations MUST NOT alter the triggers or thresholds at which compatibility mode is activated, and MUST NOT alter the behavior of the compatibility mode itself.

7.1.6. Screen Types

Device implementation screens are classified as one of two types:

Fixed-pixel display implementations: the screen is a single panel that supports only a single pixel width and height. Typically the screen is physically integrated with the device. Examples include mobile phones, tablets, and so on.
Variable-pixel display implementations: the device implementation either has no embedded screen and includes a video output port such as VGA, HDMI or a wireless port for display, or has an embedded screen that can change pixel dimensions. Examples include televisions, set-top boxes, and so on.

Fixed-Pixel Device Implementations

Fixed-pixel device implementations MAY use screens of any pixel dimensions, provided that they meet the requirements defined this Compatibility Definition.

Fixed-pixel implementations MAY include a video output port for use with an external display. However, if that display is ever used for running apps, the device MUST meet the following requirements:

The device MUST report the same screen configuration and display metrics, as detailed in Sections 7.1.1 and 7.1.2, as the fixed-pixel display.
The device MUST report the same logical density as the fixed-pixel display.
The device MUST report screen dimensions that are the same as, or very close to, the fixed-pixel display.

For example, a tablet that is 7" diagonal size with a 1024x600 pixel resolution is considered a fixed-pixel large mdpi display implementation. If it contains a video output port that displays at 720p or 1080p, the device implementation MUST scale the output so that applications are only executed in a large mdpi window, regardless of whether the fixed-pixel display or video output port is in use.

Variable-Pixel Device Implementations

Variable-pixel device implementations MUST support one or both of 1280x720, or 1920x1080 (that is, 720p or 1080p). Device implementations with variable-pixel displays MUST NOT support any other screen configuration or mode. Device implementations with variable-pixel screens MAY change screen configuration or mode at runtime or boot-time. For example, a user of a set-top box may replace a 720p display with a 1080p display, and the device implementation may adjust accordingly.

Additionally, variable-pixel device implementations MUST report the following configuration buckets for these pixel dimensions:

1280x720 (also known as 720p): 'large' screen size, 'tvdpi' (213 dpi) density
1920x1080 (also known as 1080p): 'large' screen size, 'xhdpi' (320 dpi) density

For clarity, device implementations with variable pixel dimensions are restricted to 720p or 1080p in Android 4.2, and MUST be configured to report screen size and density buckets as noted above.

7.1.7. Screen Technology

The Android platform includes APIs that allow applications to render rich graphics to the display. Devices MUST support all of these APIs as defined by the Android SDK unless specifically allowed in this document. Specifically:

Devices MUST support displays capable of rendering 16-bit color graphics and SHOULD support displays capable of 24-bit color graphics.
Devices MUST support displays capable of rendering animations.
The display technology used MUST have a pixel aspect ratio (PAR) between 0.9 and 1.1. That is, the pixel aspect ratio MUST be near square (1.0) with a 10% tolerance.

7.1.8. External Displays

Android 4.2 includes support for secondary display to enable media sharing capabilities and developer APIs for accessing external displays. If a device supports an external display either via a wired, wireless or an embedded additional display connection then the device implementation MUST implement the display manager API as described in the Android SDK documentation [ Resources, 75 ]. Device implementations that support secure video output and are capable of supporting secure surfaces MUST declare support for Display.SECURE_FLAG . Specifically, device implementations that declare support for Display.SECURE_FLAG , MUST support HDCP 2.x or higher for Miracast wireless displays or HDCP 1.2 or higher for wired displays. The upstream Android open source implementation includes support for wireless (Miracast) and wired (HDMI) displays that satisfies this requirement.

7.2. Input Devices

7.2.1. Keyboard

Device implementations:

MUST include support for the Input Management Framework (which allows third party developers to create Input Management Engines - ie soft keyboard) as detailed at http://developer.android.com
MUST provide at least one soft keyboard implementation (regardless of whether a hard keyboard is present)
MAY include additional soft keyboard implementations
MAY include a hardware keyboard
MUST NOT include a hardware keyboard that does not match one of the formats specified in android.content.res.Configuration.keyboard [ Resources, 40 ] (that is, QWERTY, or 12-key)

Device implementations:

MAY omit a non-touch navigation option (that is, may omit a trackball, d-pad, or wheel)
MUST report the correct value for android.content.res.Configuration.navigation [ Resources, 40 ]
MUST provide a reasonable alternative user interface mechanism for the selection and editing of text, compatible with Input Management Engines. The upstream Android open source implementation includes a selection mechanism suitable for use with devices that lack non-touch navigation inputs.

The Home, Menu and Back functions are essential to the Android navigation paradigm. Device implementations MUST make these functions available to the user at all times when running applications. These functions MAY be implemented via dedicated physical buttons (such as mechanical or capacitive touch buttons), or MAY be implemented using dedicated software keys, gestures, touch panel, etc. Android 4.2 supports both implementations.

Android 4.2 includes support for assist action [ Resources, 63 ]. Device implementations MUST make the assist action available to the user at all times when running applications. This function MAY be implemented via hardware or software keys.

Device implementations MAY use a distinct portion of the screen to display the navigation keys, but if so, MUST meet these requirements:

Device implementation navigation keys MUST use a distinct portion of the screen, not available to applications, and MUST NOT obscure or otherwise interfere with the portion of the screen available to applications.
Device implementations MUST make available a portion of the display to applications that meets the requirements defined in Section 7.1.1 .
Device implementations MUST display the navigation keys when applications do not specify a system UI mode, or specify SYSTEM_UI_FLAG_VISIBLE .
Device implementations MUST present the navigation keys in an unobtrusive "low profile" (eg. dimmed) mode when applications specify SYSTEM_UI_FLAG_LOW_PROFILE .
Device implementations MUST hide the navigation keys when applications specify SYSTEM_UI_FLAG_HIDE_NAVIGATION .
Device implementation MUST present a Menu key to applications when targetSdkVersion <= 10 and SHOULD NOT present a Menu key when the targetSdkVersion > 10.

7.2.4. Touchscreen input

Device implementations:

MUST have a pointer input system of some kind (either mouse-like, or touch)
MAY have a touchscreen of any modality (such as capacitive or resistive)
SHOULD support fully independently tracked pointers, if a touchscreen supports multiple pointers
MUST report the value of android.content.res.Configuration [ Resources, 39 ] reflecting corresponding to the type of the specific touchscreen on the device

Device implementations MUST report the correct feature corresponding to the type of input used. Note that Android 4.2 includes the feature android.hardware.faketouch , which corresponds to a high-fidelity non-touch (that is, pointer-based) input device such as a mouse or trackpad that can adequately emulate touch-based input (including basic gesture support), and indicates that the device supports an emulated subset of touchscreen functionality. Device implementations that include a touchscreen (single-touch or better) MUST also report android.hardware.faketouch. Device implementations that do not include a touchscreen (and rely on a pointer device only) MUST NOT report any touchscreen feature, and MUST report only android.hardware.faketouch .

7.2.5. Microphone

Device implementations MAY omit a microphone. However, if a device implementation omits a microphone, it MUST NOT report the android.hardware.microphone feature constant, and must implement the audio recording API as no-ops, per Section 7 . Conversely, device implementations that do possess a microphone:

MUST report the android.hardware.microphone feature constant
SHOULD meet the audio quality requirements in Section 5.4
SHOULD meet the audio latency requirements in Section 5.5

7.3.傳感器

Android 4.2 includes APIs for accessing a variety of sensor types. Devices implementations generally MAY omit these sensors, as provided for in the following subsections. If a device includes a particular sensor type that has a corresponding API for third-party developers, the device implementation MUST implement that API as described in the Android SDK documentation. For example, device implementations:

MUST accurately report the presence or absence of sensors per the android.content.pm.PackageManager class. [ Resources, 37 ]
MUST return an accurate list of supported sensors via the SensorManager.getSensorList() and similar methods
MUST behave reasonably for all other sensor APIs (for example, by returning true or false as appropriate when applications attempt to register listeners, not calling sensor listeners when the corresponding sensors are not present; etc.)
MUST report all sensor measurements using the relevant International System of Units (ie metric) values for each sensor type as defined in the Android SDK documentation [ Resources, 41 ]

The list above is not comprehensive; the documented behavior of the Android SDK is to be considered authoritative.

Some sensor types are synthetic, meaning they can be derived from data provided by one or more other sensors. (Examples include the orientation sensor, and the linear acceleration sensor.) Device implementations SHOULD implement these sensor types, when they include the prerequisite physical sensors.

The Android 4.2 includes a notion of a "streaming" sensor, which is one that returns data continuously, rather than only when the data changes. Device implementations MUST continuously provide periodic data samples for any API indicated by the Android 4.2 SDK documentation to be a streaming sensor. Note that the device implementations MUST ensure that the sensor stream must not prevent the device CPU from entering a suspend state or waking up from a suspend state.

7.3.1. Accelerometer

Device implementations SHOULD include a 3-axis accelerometer. If a device implementation does include a 3-axis accelerometer, it:

SHOULD be able to deliver events at 120 Hz or greater. Note that while the accelerometer frequency above is stated as "SHOULD" for Android 4.2, the Compatibility Definition for a future version is planned to change these to "MUST". That is, these standards are optional in Android 4.2 but will be required in future versions. Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 so they will be able to upgrade to the future platform releases
MUST comply with the Android sensor coordinate system as detailed in the Android APIs (see [ Resources, 41 ])
MUST be capable of measuring from freefall up to twice gravity (2g) or more on any three-dimensional vector
MUST have 8-bits of accuracy or more
MUST have a standard deviation no greater than 0.05 m/s^2

7.3.2. Magnetometer

Device implementations SHOULD include a 3-axis magnetometer (ie compass.) If a device does include a 3-axis magnetometer, it:

MUST be able to deliver events at 10 Hz or greater
MUST comply with the Android sensor coordinate system as detailed in the Android APIs (see [ Resources, 41 ]).
MUST be capable of sampling a range of field strengths adequate to cover the geomagnetic field
MUST have 8-bits of accuracy or more
MUST have a standard deviation no greater than 0.5 µT

7.3.3. GPS

Device implementations SHOULD include a GPS receiver. If a device implementation does include a GPS receiver, it SHOULD include some form of "assisted GPS" technique to minimize GPS lock-on time.

7.3.4. Gyroscope

Device implementations SHOULD include a gyroscope (ie angular change sensor.) Devices SHOULD NOT include a gyroscope sensor unless a 3-axis accelerometer is also included. If a device implementation includes a gyroscope, it:

MUST be temperature compensated
MUST be capable of measuring orientation changes up to 5.5*Pi radians/second (that is, approximately 1,000 degrees per second)
SHOULD be able to deliver events at 200 Hz or greater. Note that while the gyroscope frequency above is stated as "SHOULD" for Android 4.2, the Compatibility Definition for a future version is planned to change these to "MUST". That is, these standards are optional in Android 4.2 but will be required in future versions. Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 so they will be able to upgrade to the future platform releases
MUST have 12-bits of accuracy or more
MUST have a variance no greater than 1e-7 rad^2 / s^2 per Hz (variance per Hz, or rad^2 / s). The variance is allowed to vary with the sampling rate, but must be constrained by this value. In other words, if you measure the variance of the gyro at 1 Hz sampling rate it should be no greater than 1e-7 rad^2/s^2.
MUST have timestamps as close to when the hardware event happened as possible. The constant latency must be removed.

7.3.5. Barometer

Device implementations MAY include a barometer (ie ambient air pressure sensor.) If a device implementation includes a barometer, it:

MUST be able to deliver events at 5 Hz or greater
MUST have adequate precision to enable estimating altitude
MUST be temperature compensated

7.3.7. Thermometer

Device implementations MAY but SHOULD NOT include a thermometer (ie temperature sensor.) If a device implementation does include a thermometer, it MUST measure the temperature of the device CPU. It MUST NOT measure any other temperature. (Note that this sensor type is deprecated in the Android 4.2 APIs.)

7.3.7. Photometer

Device implementations MAY include a photometer (ie ambient light sensor.)

7.3.8. Proximity Sensor

Device implementations MAY include a proximity sensor. If a device implementation does include a proximity sensor, it MUST measure the proximity of an object in the same direction as the screen. That is, the proximity sensor MUST be oriented to detect objects close to the screen, as the primary intent of this sensor type is to detect a phone in use by the user. If a device implementation includes a proximity sensor with any other orientation, it MUST NOT be accessible through this API. If a device implementation has a proximity sensor, it MUST be have 1-bit of accuracy or more.

7.4. Data Connectivity

7.4.1. Telephony

"Telephony" as used by the Android 4.2 APIs and this document refers specifically to hardware related to placing voice calls and sending SMS messages via a GSM or CDMA network. While these voice calls may or may not be packet-switched, they are for the purposes of Android 4.2 considered independent of any data connectivity that may be implemented using the same network. In other words, the Android "telephony" functionality and APIs refer specifically to voice calls and SMS; for instance, device implementations that cannot place calls or send/receive SMS messages MUST NOT report the "android.hardware.telephony" feature or any sub-features, regardless of whether they use a cellular network for data connectivity.

Android 4.2 MAY be used on devices that do not include telephony hardware. That is, Android 4.2 is compatible with devices that are not phones. However, if a device implementation does include GSM or CDMA telephony, it MUST implement full support for the API for that technology. Device implementations that do not include telephony hardware MUST implement the full APIs as no-ops.

7.4.2. IEEE 802.11 (WiFi)

Android 4.2 device implementations SHOULD include support for one or more forms of 802.11 (b/g/a/n, etc.) If a device implementation does include support for 802.11, it MUST implement the corresponding Android API.

Device implementations MUST implement the multicast API as described in the SDK documentation [ Resources, 62 ]. Device implementations that do include Wifi support MUST support multicast DNS (mDNS). Device implementations MUST not filter mDNS packets (224.0.0.251) at any time of operation including when the screen is not in an active state.

7.4.2.1. WiFi Direct

Device implementations SHOULD include support for Wifi direct (Wifi peer-to-peer). If a device implementation does include support for Wifi direct, it MUST implement the corresponding Android API as described in the SDK documentation [ Resources, 68 ]. If a device implementation includes support for Wifi direct, then it:

MUST support regular Wifi operation
SHOULD support concurrent wifi and wifi Direct operation

7.4.3.藍牙

Device implementations SHOULD include a Bluetooth transceiver. Device implementations that do include a Bluetooth transceiver MUST enable the RFCOMM-based Bluetooth API as described in the SDK documentation [ Resources, 42 ]. Device implementations SHOULD implement relevant Bluetooth profiles, such as A2DP, AVRCP, OBEX, etc. as appropriate for the device.

The Compatibility Test Suite includes cases that cover basic operation of the Android RFCOMM Bluetooth API. However, since Bluetooth is a communications protocol between devices, it cannot be fully tested by unit tests running on a single device. Consequently, device implementations MUST also pass the human-driven Bluetooth test procedure described in Appendix A.

7.4.4. Near-Field Communications

Device implementations SHOULD include a transceiver and related hardware for Near-Field Communications (NFC). If a device implementation does include NFC hardware, then it:

MUST report the android.hardware.nfc feature from the android.content.pm.PackageManager.hasSystemFeature() method. [ Resources, 37 ]
MUST be capable of reading and writing NDEF messages via the following NFC standards:
- MUST be capable of acting as an NFC Forum reader/writer (as defined by the NFC Forum technical specification NFCForum-TS-DigitalProtocol-1.0) via the following NFC standards:
  - NfcA (ISO14443-3A)
  - NfcB (ISO14443-3B)
  - NfcF (JIS 6319-4)
  - IsoDep (ISO 14443-4)
  - NFC Forum Tag Types 1, 2, 3, 4 (defined by the NFC Forum)
SHOULD be capable of reading and writing NDEF messages via the following NFC standards. Note that while the NFC standards below are stated as "SHOULD" for Android 4.2, the Compatibility Definition for a future version is planned to change these to "MUST". That is, these standards are optional in Android 4.2 but will be required in future versions. Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 so they will be able to upgrade to the future platform releases.
- NfcV (ISO 15693)
MUST be capable of transmitting and receiving data via the following peer-to-peer standards and protocols:
- ISO 18092
- LLCP 1.0 (defined by the NFC Forum)
- SDP 1.0 (defined by the NFC Forum)
- NDEF Push Protocol [ Resources, 43 ]
- SNEP 1.0 (defined by the NFC Forum)
MUST include support for Android Beam [ Resources, 65 ]:
- MUST implement the SNEP default server. Valid NDEF messages received by the default SNEP server MUST be dispatched to applications using the android.nfc.ACTION_NDEF_DISCOVERED intent. Disabling Android Beam in settings MUST NOT disable dispatch of incoming NDEF message.
- Device implementations MUST honor the android.settings.NFCSHARING_SETTINGS intent to show NFC sharing settings [ Resources, 67 ].
- MUST implement the NPP server. Messages received by the NPP server MUST be processed the same way as the SNEP default server.
- MUST implement a SNEP client and attempt to send outbound P2P NDEF to the default SNEP server when Android Beam is enabled. If no default SNEP server is found then the client MUST attempt to send to an NPP server.
- MUST allow foreground activities to set the outbound P2P NDEF message using android.nfc.NfcAdapter.setNdefPushMessage, and android.nfc.NfcAdapter.setNdefPushMessageCallback, and android.nfc.NfcAdapter.enableForegroundNdefPush.
- SHOULD use a gesture or on-screen confirmation, such as 'Touch to Beam', before sending outbound P2P NDEF messages.
- SHOULD enable Android Beam by default
- MUST support NFC Connection handover to Bluetooth when the device supports Bluetooth Object Push Profile. Device implementations must support connection handover to Bluetooth when using android.nfc.NfcAdapter.setBeamPushUris, by implementing the "Connection Handover version 1.2" [ Resources, 60 ] and "Bluetooth Secure Simple Pairing Using NFC version 1.0" [ Resources, 61 ] specs from the NFC Forum. Such an implementation SHOULD use SNEP GET requests for exchanging the handover request / select records over NFC, and it MUST use the Bluetooth Object Push Profile for the actual Bluetooth data transfer.
MUST poll for all supported technologies while in NFC discovery mode.
SHOULD be in NFC discovery mode while the device is awake with the screen active and the lock-screen unlocked.

(Note that publicly available links are not available for the JIS, ISO, and NFC Forum specifications cited above.)

Additionally, device implementations MAY include reader/writer support for the following MIFARE technologies.

MIFARE Classic (NXP MF1S503x [ Resources, 44 ], MF1S703x [ Resources, 44 ])
MIFARE Ultralight (NXP MF0ICU1 [ Resources, 46 ], MF0ICU2 [ Resources, 46 ])
NDEF on MIFARE Classic (NXP AN130511 [ Resources, 48 ], AN130411 [ Resources, 49 ])

Note that Android 4.2 includes APIs for these MIFARE types. If a device implementation supports MIFARE in the reader/writer role, it:

MUST implement the corresponding Android APIs as documented by the Android SDK
MUST report the feature com.nxp.mifare from the android.content.pm.PackageManager.hasSystemFeature() method. [ Resources, 37 ] Note that this is not a standard Android feature, and as such does not appear as a constant on the PackageManager class.
MUST NOT implement the corresponding Android APIs nor report the com.nxp.mifare feature unless it also implements general NFC support as described in this section

If a device implementation does not include NFC hardware, it MUST NOT declare the android.hardware.nfc feature from the android.content.pm.PackageManager.hasSystemFeature() method [ Resources, 37 ], and MUST implement the Android 4.2 NFC API as a no-op.

As the classes android.nfc.NdefMessage and android.nfc.NdefRecord represent a protocol-independent data representation format, device implementations MUST implement these APIs even if they do not include support for NFC or declare the android.hardware.nfc feature.

7.4.5. Minimum Network Capability

Device implementations MUST include support for one or more forms of data networking. Specifically, device implementations MUST include support for at least one data standard capable of 200Kbit/sec or greater. Examples of technologies that satisfy this requirement include EDGE, HSPA, EV-DO, 802.11g, Ethernet, etc.

Device implementations where a physical networking standard (such as Ethernet) is the primary data connection SHOULD also include support for at least one common wireless data standard, such as 802.11 (WiFi).

Devices MAY implement more than one form of data connectivity.

7.5. Cameras

Device implementations SHOULD include a rear-facing camera, and MAY include a front-facing camera. A rear-facing camera is a camera located on the side of the device opposite the display; that is, it images scenes on the far side of the device, like a traditional camera. A front-facing camera is a camera located on the same side of the device as the display; that is, a camera typically used to image the user, such as for video conferencing and similar applications.

7.5.1. Rear-Facing Camera

Device implementations SHOULD include a rear-facing camera. If a device implementation includes a rear-facing camera, it:

MUST have a resolution of at least 2 megapixels
SHOULD have either hardware auto-focus, or software auto-focus implemented in the camera driver (transparent to application software)
MAY have fixed-focus or EDOF (extended depth of field) hardware
MAY include a flash. If the Camera includes a flash, the flash lamp MUST NOT be lit while an android.hardware.Camera.PreviewCallback instance has been registered on a Camera preview surface, unless the application has explicitly enabled the flash by enabling the FLASH_MODE_AUTO or FLASH_MODE_ON attributes of a Camera.Parameters object. Note that this constraint does not apply to the device's built-in system camera application, but only to third-party applications using Camera.PreviewCallback .

7.5.2. Front-Facing Camera

Device implementations MAY include a front-facing camera. If a device implementation includes a front-facing camera, it:

MUST have a resolution of at least VGA (that is, 640x480 pixels)
MUST NOT use a front-facing camera as the default for the Camera API. That is, the camera API in Android 4.2 has specific support for front-facing cameras, and device implementations MUST NOT configure the API to to treat a front-facing camera as the default rear-facing camera, even if it is the only camera on the device.
MAY include features (such as auto-focus, flash, etc.) available to rear-facing cameras as described in Section 7.5.1.
MUST horizontally reflect (ie mirror) the stream displayed by an app in a CameraPreview, as follows:

If the device implementation is capable of being rotated by user (such as automatically via an accelerometer or manually via user input), the camera preview MUST be mirrored horizontally relative to the device's current orientation.
If the current application has explicitly requested that the Camera display be rotated via a call to the android.hardware.Camera.setDisplayOrientation() [ Resources, 50 ] method, the camera preview MUST be mirrored horizontally relative to the orientation specified by the application.
Otherwise, the preview MUST be mirrored along the device's default horizontal axis.

MUST mirror the image displayed by the postview in the same manner as the camera preview image stream. (If the device implementation does not support postview, this requirement obviously does not apply.)
MUST NOT mirror the final captured still image or video streams returned to application callbacks or committed to media storage

7.5.3. Camera API Behavior

Device implementations MUST implement the following behaviors for the camera-related APIs, for both front- and rear-facing cameras:

If an application has never called android.hardware.Camera.Parameters.setPreviewFormat(int) , then the device MUST use android.hardware.PixelFormat.YCbCr_420_SP for preview data provided to application callbacks.
If an application registers an android.hardware.Camera.PreviewCallback instance and the system calls the onPreviewFrame() method when the preview format is YCbCr_420_SP, the data in the byte[] passed into onPreviewFrame() must further be in the NV21 encoding format. That is, NV21 MUST be the default.
Device implementations MUST support the YV12 format (as denoted by the android.graphics.ImageFormat.YV12 constant) for camera previews for both front- and rear-facing cameras. (The hardware video encoder and camera may use any native pixel format, but the device implementation MUST support conversion to YV12.)

Device implementations MUST implement the full Camera API included in the Android 4.2 SDK documentation [ Resources, 51 ]), regardless of whether the device includes hardware autofocus or other capabilities. For instance, cameras that lack autofocus MUST still call any registered android.hardware.Camera.AutoFocusCallback instances (even though this has no relevance to a non-autofocus camera.) Note that this does apply to front-facing cameras; for instance, even though most front-facing cameras do not support autofocus, the API callbacks must still be "faked" as described.

Device implementations MUST recognize and honor each parameter name defined as a constant on the android.hardware.Camera.Parameters class, if the underlying hardware supports the feature. If the device hardware does not support a feature, the API must behave as documented. Conversely, Device implementations MUST NOT honor or recognize string constants passed to the android.hardware.Camera.setParameters() method other than those documented as constants on the android.hardware.Camera.Parameters . That is, device implementations MUST support all standard Camera parameters if the hardware allows, and MUST NOT support custom Camera parameter types. For instance, device implementations that support image capture using high dynamic range (HDR) imaging techniques MUST support camera parameter Camera.SCENE_MODE_HDR [ Resources, 78 ]).

Device implementations MUST broadcast the Camera.ACTION_NEW_PICTURE intent whenever a new picture is taken by the camera and the entry of the picture has been added to the media store.

Device implementations MUST broadcast the Camera.ACTION_NEW_VIDEO intent whenever a new video is recorded by the camera and the entry of the picture has been added to the media store.

7.5.4. Camera Orientation

Both front- and rear-facing cameras, if present, MUST be oriented so that the long dimension of the camera aligns with the screen's long dimention. That is, when the device is held in the landscape orientation, cameras MUST capture images in the landscape orientation. This applies regardless of the device's natural orientation; that is, it applies to landscape-primary devices as well as portrait-primary devices.

7.6. Memory and Storage

7.6.1. Minimum Memory and Storage

Device implementations MUST have at least 340MB of memory available to the kernel and userspace. The 340MB MUST be in addition to any memory dedicated to hardware components such as radio, video, and so on that is not under the kernel's control.

Device implementations MUST have at least 350MB of non-volatile storage available for application private data. That is, the /data partition MUST be at least 350MB.

The Android APIs include a Download Manager that applications may use to download data files [ Resources, 56 ]. The device implementation of the Download Manager MUST be capable of downloading individual files of at least 100MB in size to the default "cache" location.

7.6.2. Application Shared Storage

Device implementations MUST offer shared storage for applications. The shared storage provided MUST be at least 1GB in size.

Device implementations MUST be configured with shared storage mounted by default, "out of the box". If the shared storage is not mounted on the Linux path /sdcard , then the device MUST include a Linux symbolic link from /sdcard to the actual mount point.

Device implementations MUST enforce as documented the android.permission.WRITE_EXTERNAL_STORAGE permission on this shared storage. Shared storage MUST otherwise be writable by any application that obtains that permission.

Device implementations MAY have hardware for user-accessible removable storage, such as a Secure Digital card. Alternatively, device implementations MAY allocate internal (non-removable) storage as shared storage for apps.

Regardless of the form of shared storage used, device implementations MUST provide some mechanism to access the contents of shared storage from a host computer, such as USB mass storage (UMS) or Media Transfer Protocol (MTP). Device implementations MAY use USB mass storage, but SHOULD use Media Transfer Protocol. If the device implementation supports Media Transfer Protocol:

The device implementation SHOULD be compatible with the reference Android MTP host, Android File Transfer [ Resources, 57 ].
The device implementation SHOULD report a USB device class of 0x00 .
The device implementation SHOULD report a USB interface name of 'MTP'.

If the device implementation lacks USB ports, it MUST provide a host computer with access to the contents of shared storage by some other means, such as a network file system.

It is illustrative to consider two common examples. If a device implementation includes an SD card slot to satisfy the shared storage requirement, a FAT-formatted SD card 1GB in size or larger MUST be included with the device as sold to users, and MUST be mounted by default. Alternatively, if a device implementation uses internal fixed storage to satisfy this requirement, that storage MUST be 1GB in size or larger and mounted on /sdcard (or /sdcard MUST be a symbolic link to the physical location if it is mounted elsewhere.)

Device implementations that include multiple shared storage paths (such as both an SD card slot and shared internal storage) SHOULD modify the core applications such as the media scanner and ContentProvider to transparently support files placed in both locations.

7.7. USB

Device implementations SHOULD include a USB client port, and SHOULD include a USB host port.

If a device implementation includes a USB client port:

the port MUST be connectable to a USB host with a standard USB-A port
the port SHOULD use the micro USB form factor on the device side. Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 so they will be able to upgrade to the future platform releases
the port SHOULD be centered in the middle of an edge. Device implementations SHOULD either locate the port on the bottom of the device (according to natural orientation) or enable software screen rotation for all apps (including home screen), so that the display draws correctly when the device is oriented with the port at bottom. Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 so they will be able to upgrade to future platform releases.
if the device has other ports (such as a non-USB charging port) it SHOULD be on the same edge as the micro-USB port
it MUST allow a host connected to the device to access the contents of the shared storage volume using either USB mass storage or Media Transfer Protocol
it MUST implement the Android Open Accessory API and specification as documented in the Android SDK documentation, and MUST declare support for the hardware feature android.hardware.usb.accessory [ Resources, 52 ]
it MUST implement the USB audio class as documented in the Android SDK documentation [ Resources, 66 ]
it SHOULD implement support for USB battery charging specification [ Resources, 64 ] Existing and new devices that run Android 4.2 are very strongly encouraged to meet these requirements in Android 4.2 so they will be able to upgrade to the future platform releases

If a device implementation includes a USB host port:

it MAY use a non-standard port form factor, but if so MUST ship with a cable or cables adapting the port to standard USB-A
it MUST implement the Android USB host API as documented in the Android SDK, and MUST declare support for the hardware feature android.hardware.usb.host [ Resources, 53 ]

Device implementations MUST implement the Android Debug Bridge. If a device implementation omits a USB client port, it MUST implement the Android Debug Bridge via local-area network (such as Ethernet or 802.11)

8. Performance Compatibility

Device implementations MUST meet the key performance metrics of an Android 4.2 compatible device defined in the table below:

Metric	Performance Threshold	Comments
Application Launch Time	The following applications should launch within the specified time. Browser: less than 1300ms Contacts: less than 700ms Settings: less than 700ms	The launch time is measured as the total time to complete loading the default activity for the application, including the time it takes to start the Linux process, load the Android package into the Dalvik VM, and call onCreate.
Simultaneous Applications	When multiple applications have been launched, re-launching an already-running application after it has been launched must take less than the original launch time.

9. Security Model Compatibility

Device implementations MUST implement a security model consistent with the Android platform security model as defined in Security and Permissions reference document in the APIs [ Resources, 54 ] in the Android developer documentation. Device implementations MUST support installation of self-signed applications without requiring any additional permissions/certificates from any third parties/authorities. Specifically, compatible devices MUST support the security mechanisms described in the follow sub-sections.

9.1. Permissions

Device implementations MUST support the Android permissions model as defined in the Android developer documentation [ Resources, 54 ]. Specifically, implementations MUST enforce each permission defined as described in the SDK documentation; no permissions may be omitted, altered, or ignored. Implementations MAY add additional permissions, provided the new permission ID strings are not in the android.* namespace.

9.2. UID and Process Isolation

Device implementations MUST support the Android application sandbox model, in which each application runs as a unique Unix-style UID and in a separate process. Device implementations MUST support running multiple applications as the same Linux user ID, provided that the applications are properly signed and constructed, as defined in the Security and Permissions reference [ Resources, 54 ].

9.3. Filesystem Permissions

Device implementations MUST support the Android file access permissions model as defined in as defined in the Security and Permissions reference [ Resources, 54 ].

9.4. Alternate Execution Environments

Device implementations MAY include runtime environments that execute applications using some other software or technology than the Dalvik virtual machine or native code. However, such alternate execution environments MUST NOT compromise the Android security model or the security of installed Android applications, as described in this section.

Alternate runtimes MUST themselves be Android applications, and abide by the standard Android security model, as described elsewhere in Section 9.

Alternate runtimes MUST NOT be granted access to resources protected by permissions not requested in the runtime's AndroidManifest.xml file via the <uses-permission> mechanism.

Alternate runtimes MUST NOT permit applications to make use of features protected by Android permissions restricted to system applications.

Alternate runtimes MUST abide by the Android sandbox model. Specifically:

Alternate runtimes SHOULD install apps via the PackageManager into separate Android sandboxes (that is, Linux user IDs, etc.)
Alternate runtimes MAY provide a single Android sandbox shared by all applications using the alternate runtime
Alternate runtimes and installed applications using an alternate runtime MUST NOT reuse the sandbox of any other app installed on the device, except through the standard Android mechanisms of shared user ID and signing certificate
Alternate runtimes MUST NOT launch with, grant, or be granted access to the sandboxes corresponding to other Android applications

Alternate runtimes MUST NOT be launched with, be granted, or grant to other applications any privileges of the superuser (root), or of any other user ID.

The .apk files of alternate runtimes MAY be included in the system image of a device implementation, but MUST be signed with a key distinct from the key used to sign other applications included with the device implementation.

When installing applications, alternate runtimes MUST obtain user consent for the Android permissions used by the application. That is, if an application needs to make use of a device resource for which there is a corresponding Android permission (such as Camera, GPS, etc.), the alternate runtime MUST inform the user that the application will be able to access that resource. If the runtime environment does not record application capabilities in this manner, the runtime environment MUST list all permissions held by the runtime itself when installing any application using that runtime.

9.5. Multi-User Support

Android 4.2 includes support for multiple users and provides support for full user isolation [ Resources, 70 ].

Device implementations MUST meet these requirements related to multi-user support[ Resources, 71 ]:

As the behavior of the telephony APIs on devices with multiple users is currently undefined, device implementations that declare android.hardware.telephony MUST NOT enable multi-user support.
Device implementations MUST, for each user, implement a security model consistent with the Android platform security model as defined in Security and Permissions reference document in the APIs [Resources, 54]

Each user instance on an Android device MUST have separate and isolated external storage directories. Device implementations MAY store multiple users' data on the same volume or filesystem. However, the device implementation MUST ensure that applications owned by and running on behalf a given user cannot list, read, or write to data owned by any other user. Note that removable media, such as SD card slots, can allow one user to access another's data by means of a host PC. For this reason, device implementations that use removable media for the external storage APIs MUST encrypt the contents of the SD card if multi-user is enabled using a key stored only on non-removable media accessible only to the system. As this will make the media unreadable by a host PC, device implementations will be required to switch to MTP or a similar system to provide host PCs with access to the current user's data. Accordingly, device implementations MAY but SHOULD NOT enable multi-user if they use removable media [ Resources, 72 ] for primary external storage. The upstream Android open-source project includes an implementation that uses internal device storage for application external storage APIs; device implementations SHOULD use this configuration and software implementation. Device implementations that include multiple external storage paths MUST NOT allow Android applications to write to the secondary external storage

9.6. Premium SMS Warning

Android 4.2 includes support for warning users for any outgoing premium SMS message. Premium SMS messages are text messages sent to a service registered with a carrier that may incur a charge to the user. Device implementations that declare support for android.hardware.telephony MUST warn users before sending a SMS message to numbers identified by regular expressions defined in /data/misc/sms/codes.xml file in the device. The upstream Android open-source project provides an implementation that satisfies this requirement.

10. Software Compatibility Testing

Device implementations MUST pass all tests described in this section.

However, note that no software test package is fully comprehensive. For this reason, device implementers are very strongly encouraged to make the minimum number of changes as possible to the reference and preferred implementation of Android 4.2 available from the Android Open Source Project. This will minimize the risk of introducing bugs that create incompatibilities requiring rework and potential device updates.

10.1. Compatibility Test Suite

Device implementations MUST pass the Android Compatibility Test Suite (CTS) [ Resources, 2 ] available from the Android Open Source Project, using the final shipping software on the device. Additionally, device implementers SHOULD use the reference implementation in the Android Open Source tree as much as possible, and MUST ensure compatibility in cases of ambiguity in CTS and for any reimplementations of parts of the reference source code.

The CTS is designed to be run on an actual device. Like any software, the CTS may itself contain bugs. The CTS will be versioned independently of this Compatibility Definition, and multiple revisions of the CTS may be released for Android 4.2. Device implementations MUST pass the latest CTS version available at the time the device software is completed.

10.2. CTS Verifier

Device implementations MUST correctly execute all applicable cases in the CTS Verifier. The CTS Verifier is included with the Compatibility Test Suite, and is intended to be run by a human operator to test functionality that cannot be tested by an automated system, such as correct functioning of a camera and sensors.

The CTS Verifier has tests for many kinds of hardware, including some hardware that is optional. Device implementations MUST pass all tests for hardware which they possess; for instance, if a device possesses an accelerometer, it MUST correctly execute the Accelerometer test case in the CTS Verifier. Test cases for features noted as optional by this Compatibility Definition Document MAY be skipped or omitted.

Every device and every build MUST correctly run the CTS Verifier, as noted above. However, since many builds are very similar, device implementers are not expected to explicitly run the CTS Verifier on builds that differ only in trivial ways. Specifically, device implementations that differ from an implementation that has passed the CTS Verfier only by the set of included locales, branding, etc. MAY omit the CTS Verifier test.

10.3. Reference Applications

Device implementers MUST test implementation compatibility using the following open source applications:

The "Apps for Android" applications [ Resources, 55 ]
Replica Island (available in Android Market)

Each app above MUST launch and behave correctly on the implementation, for the implementation to be considered compatible.

11. Updatable Software

Device implementations MUST include a mechanism to replace the entirety of the system software. The mechanism need not perform "live" upgrades - that is, a device restart MAY be required.

Any method can be used, provided that it can replace the entirety of the software preinstalled on the device. For instance, any of the following approaches will satisfy this requirement:

Over-the-air (OTA) downloads with offline update via reboot
"Tethered" updates over USB from a host PC
"Offline" updates via a reboot and update from a file on removable storage

The update mechanism used MUST support updates without wiping user data. That is, the update mechanism MUST preserve application private data and application shared data. Note that the upstream Android software includes an update mechanism that satisfies this requirement.

If an error is found in a device implementation after it has been released but within its reasonable product lifetime that is determined in consultation with the Android Compatibility Team to affect the compatibility of third-party applications, the device implementer MUST correct the error via a software update available that can be applied per the mechanism just described.

12. Contact Us

You can contact the document authors at compatibility@android.com for clarifications and to bring up any issues that you think the document does not cover.

Appendix A - Bluetooth Test Procedure

The test procedure is based on the BluetoothChat sample app included in the Android open source project tree. The procedure requires two devices:

a candidate device implementation running the software build to be tested
a separate device implementation already known to be compatible, and of a model from the device implementation being tested - that is, a "known good" device implementation

The test procedure below refers to these devices as the "candidate" and "known good" devices, respectively.

Setup and Installation

Build BluetoothChat.apk via 'make samples' from an Android source code tree
Install BluetoothChat.apk on the known-good device
Install BluetoothChat.apk on the candidate device

Test Bluetooth Control by Apps

Launch BluetoothChat on the candidate device, while Bluetooth is disabled
Verify that the candidate device either turns on Bluetooth, or prompts the user with a dialog to turn on Bluetooth

Test Pairing and Communication

Launch the Bluetooth Chat app on both devices
Make the known-good device discoverable from within BluetoothChat (using the Menu)
On the candidate device, scan for Bluetooth devices from within BluetoothChat (using the Menu) and pair with the known-good device
Send 10 or more messages from each device, and verify that the other device receives them correctly
Close the BluetoothChat app on both devices by pressing Home
Unpair each device from the other, using the device Settings app

Test Pairing and Communication in the Reverse Direction

Launch the Bluetooth Chat app on both devices.
Make the candidate device discoverable from within BluetoothChat (using the Menu).
On the known-good device, scan for Bluetooth devices from within BluetoothChat (using the Menu) and pair with the candidate device.
Send 10 or messages from each device, and verify that the other device receives them correctly.
Close the Bluetooth Chat app on both devices by pressing Back repeatedly to get to the Launcher.

Test Re-Launches

Re-launch the Bluetooth Chat app on both devices.
Send 10 or messages from each device, and verify that the other device receives them correctly.

Note: the above tests have some cases which end a test section by using Home, and some using Back. These tests are not redundant and are not optional: the objective is to verify that the Bluetooth API and stack works correctly both when Activities are explicitly terminated (via the user pressing Back, which calls finish()), and implicitly sent to background (via the user pressing Home.) Each test sequence MUST be performed as described.

Android 4.2 兼容性定義

目錄

一、簡介

2. 資源

3. 軟件

3.1。託管 API 兼容性

3.2.軟 API 兼容性

3.2.1。權限

3.2.2.構建參數

3.2.3。意圖兼容性

3.2.3.1。核心應用意圖

3.2.3.2。意圖覆蓋

3.2.3.3。意圖命名空間

3.2.3.4。廣播意圖

3.3.原生 API 兼容性

3.3.1 應用二進制接口

3.4.網絡兼容性

3.4.1。 Web 視圖兼容性

3.4.2.瀏覽器兼容性

3.5. API 行為兼容性

3.6. API 命名空間

3.7. Virtual Machine Compatibility

3.8. User Interface Compatibility

3.8.1. Widgets

3.8.2. Notifications

3.8.3. Search

3.8.4. Toasts

3.8.5. Themes

3.8.6. Live Wallpapers

3.8.7. Recent Application Display

3.8.8. Input Management Settings

3.8.9. Lock and Home Screen Widgets

3.8.10. Lock Screen Media Remote Control

3.8.11. Dreams

3.9 Device Administration

3.10 Accessibility

3.11 Text-to-Speech

4. Application Packaging Compatibility

5. Multimedia Compatibility

5.1. Media Codecs

5.2 Video Encoding

5.3 Video Decoding

5.4. Audio Recording

5.5. Audio Latency

5.6. Network Protocols

6. Developer Tools and Options Compatibility

6.1 Developer Tools

6.2 Developer Options

7. Hardware Compatibility

7.1. Display and Graphics

7.1.1. Screen Configuration

7.1.2. Display Metrics

7.1.3. Screen Orientation

7.1.4. 2D and 3D Graphics Acceleration

7.1.5. Legacy Application Compatibility Mode

7.1.6. Screen Types

7.1.7. Screen Technology

7.1.8. External Displays

7.2. Input Devices

7.2.1. Keyboard

7.2.2. Non-touch Navigation

7.2.3. Navigation keys

7.2.4. Touchscreen input

7.2.5. Microphone

7.3.傳感器

7.3.1. Accelerometer

7.3.2. Magnetometer

7.3.3. GPS

7.3.4. Gyroscope

7.3.5. Barometer

7.3.7. Thermometer

7.3.7. Photometer

7.3.8. Proximity Sensor

7.4. Data Connectivity

7.4.1. Telephony

7.4.2. IEEE 802.11 (WiFi)

7.4.2.1. WiFi Direct

7.4.3.藍牙

7.4.4. Near-Field Communications

7.4.5. Minimum Network Capability