行為變更：所有應用程式

Android 14 平台包含可能對應用程式造成影響的行為變更。無論 targetSdkVersion 為何，當應用程式在 Android 14 上執行時，下列行為變更將會套用至所有應用程式。您應測試應用程式，並視需要修改，以便在適當情況下支援新版本功能。

另請務必查看僅對指定 Android 14 為目標版本的應用程式造成影響的行為變更。

核心功能

根據預設，系統會拒絕排定精確鬧鐘

精確鬧鐘是針對使用者需求或需要在確切時間發生的操作所設計的通知。自 Android 14 起，SCHEDULE_EXACT_ALARM 權限不再預先授予以 Android 13 以上版本為目標所安裝的最新應用程式；該權限依預設為拒絕狀態。

進一步瞭解精準鬧鐘排程權限變更。

在應用程式快取期間，註冊使用情境的廣播訊息會排入佇列

在 Android 14 中，當應用程式處於快取狀態時，系統可以將已註冊使用情境的廣播訊息排入佇列。這類似於佇列 Android 12 (API 級別 31) 為非同步繫結器引入的行為 交易系統不會將宣告資訊清單的廣播訊息排入佇列，而且應用程式會遭到移除 以便進行廣播傳遞

當應用程式結束快取狀態 (例如返回前景時)， 系統會傳送所有排入佇列的廣播訊息某些廣播訊息的多個執行個體可以合併為單一廣播訊息。根據其他因素，例如系統 健康狀態、應用程式可能會從快取狀態中移除， 廣播訊息

應用程式只能終止自己的背景處理程序

自 Android 14 起，當應用程式呼叫 killBackgroundProcesses() 時， API 只能終止您自有應用程式的背景處理程序。

如果傳入其他應用程式的套件名稱，此方法不會 ，而 Logcat 中會顯示以下訊息：

Invalid packageName: com.example.anotherapp

您的應用程式不應使用 killBackgroundProcesses() API，或嘗試影響其他應用程式的處理程序生命週期，即使是在舊版 OS 上也是如此。Android 的設計是為了在背景作業中保留快取的應用程式，並且能夠在系統需要記憶體時自動終止這些應用程式。如果您的應用程式不小心關閉其他應用程式，可能會因為需要在稍後重新啟動這些應用程式 (比起恢復現有已快取的應用程式會耗用更多的資源)，進而降低系統效能並增加電池用量。

針對第一個要求 MTU 的 GATT 用戶端，MTU 會設為 517

Starting from Android 14, the Android Bluetooth stack more strictly adheres to Version 5.2 of the Bluetooth Core Specification and requests the BLE ATT MTU to 517 bytes when the first GATT client requests an MTU using the BluetoothGatt#requestMtu(int) API, and disregards all subsequent MTU requests on that ACL connection.

To address this change and make your app more robust, consider the following options:

  • Your peripheral device should respond to the Android device's MTU request with a reasonable value that can be accommodated by the peripheral. The final negotiated value will be a minimum of the Android requested value and the remote provided value (for example, min(517, remoteMtu))
    • Implementing this fix could require a firmware update for peripheral
  • Alternatively, limit your GATT characteristic writes based on the minimum between the known supported value of your peripheral and the received MTU change
    • A reminder that you should reduce 5 bytes from the supported size for the headers
    • For example: arrayMaxLength = min(SUPPORTED_MTU, GATT_MAX_ATTR_LEN(517)) - 5

應用程式可能排入受限制待命值區的新原因

Android 14 推出了應用程式可放入受限制待命值區的新原因。應用程式的工作因 onStartJob、onStopJob 或 onBind 方法逾時而多次觸發 ANR 錯誤。(如要瞭解 onStartJob 和 onStopJob 的變更，請參閱「JobScheduler 強化回呼和網路行為」)。

如要追蹤應用程式是否已進入受限制的待機區塊，建議您在工作執行時使用 API UsageStatsManager.getAppStandbyBucket() 進行記錄，或在應用程式啟動時使用 UsageStatsManager.queryEventsForSelf()。

mlock 上限為 64 KB

在 Android 14 (API 級別 34) 以上版本中，平台會將可使用 mlock() 鎖定的最大記憶體量，從每個程序 64 KB 降至 64 KB。在先前版本中，每個程序的限制為 64 MB。這項限制可促進應用程式和系統的記憶體管理。為在各裝置上提供更一致的體驗，Android 14 新增了新的 CTS 測試，針對相容裝置的新 mlock() 限制進行測試。

系統會強制執行快取應用程式的資源用量

By design, an app's process is in a cached state when it's moved to the background and no other app process components are running. Such an app process is subject to being killed due to system memory pressure. Any work that Activity instances perform after the onStop() method has been called and returned, while in this state, is unreliable and strongly discouraged.

Android 14 introduces consistency and enforcement to this design. Shortly after an app process enters a cached state, background work is disallowed, until a process component re-enters an active state of the lifecycle.

Apps that use typical framework-supported lifecycle APIs – such as services, JobScheduler, and Jetpack WorkManager – shouldn't be impacted by these changes.

使用者體驗

關於使用者無法關閉通知的變更

If your app shows non-dismissable foreground notifications to users, Android 14 has changed the behavior to allow users to dismiss such notifications.

This change applies to apps that prevent users from dismissing foreground notifications by setting Notification.FLAG_ONGOING_EVENT through Notification.Builder#setOngoing(true) or NotificationCompat.Builder#setOngoing(true). The behavior of FLAG_ONGOING_EVENT has changed to make such notifications actually dismissable by the user.

These kinds of notifications are still non-dismissable in the following conditions:

  • When the phone is locked
  • If the user selects a Clear all notification action (which helps with accidental dismissals)

Also, this new behavior doesn't apply to notifications in the following use cases:

  • CallStyle notifications
  • Device policy controller (DPC) and supporting packages for enterprise
  • Media notifications
  • The default Search Selector package

以更清楚的方式顯示資料安全性資訊

為了加強使用者隱私，Android 14 會增加系統顯示您在 Play 管理中心表單中宣告的資訊地點數量。目前，使用者可以在 Google Play 應用程式商店資訊的「資料安全性」專區中查看這項資訊。

建議您查看應用程式的位置資料分享政策，並撥冗為應用程式的 Google Play 資料安全性專區進行適用的更新。

詳情請參閱這份指南，瞭解 Android 14 如何以更清楚的方式顯示資料安全性資訊。

無障礙設定

非線性字型縮放至 200%

Starting in Android 14, the system supports font scaling up to 200%, providing low-vision users with additional accessibility options that align with Web Content Accessibility Guidelines (WCAG).

If you already use scaled pixels (sp) units to define text sizing, then this change probably won't have a high impact on your app. However, you should perform UI testing with the maximum font size enabled (200%) to ensure that your app can accommodate larger font sizes without impacting usability.

安全性

可安裝的目標 API 級別下限

Starting with Android 14, apps with a targetSdkVersion lower than 23 can't be installed. Requiring apps to meet these minimum target API level requirements improves security and privacy for users.

Malware often targets older API levels in order to bypass security and privacy protections that have been introduced in newer Android versions. For example, some malware apps use a targetSdkVersion of 22 to avoid being subjected to the runtime permission model introduced in 2015 by Android 6.0 Marshmallow (API level 23). This Android 14 change makes it harder for malware to avoid security and privacy improvements. Attempting to install an app targeting a lower API level will result in an installation failure, with the following message appearing in Logcat:

INSTALL_FAILED_DEPRECATED_SDK_VERSION: App package must target at least SDK version 23, but found 7

On devices upgrading to Android 14, any apps with a targetSdkVersion lower than 23 will remain installed.

If you need to test an app targeting an older API level, use the following ADB command:

adb install --bypass-low-target-sdk-block FILENAME.apk

媒體擁有者的套件名稱可能會被遮蓋

您可以使用媒體儲存區查詢列有儲存特定媒體檔案應用程式的 OWNER_PACKAGE_NAME 資料欄。自 Android 14 版本起，除非符合下列至少一項條件，否則系統將遮蓋此值：

  • 儲存媒體檔案的應用程式會具備一律可由其他應用程式瀏覽的套件名稱。

  • 查詢媒體儲存區的應用程式會要求 QUERY_ALL_PACKAGES 權限。

進一步瞭解 Android 如何篩選套件的瀏覽權限，以保護隱私權。