行为变更：所有应用

Android 14 平台包含一些行为变更，这些变更可能会影响您的应用。以下行为变更将影响在 Android 14 上运行的所有应用，无论采用哪种 targetSdkVersion 都不例外。您应该测试您的应用，然后根据需要进行修改，以适当地支持这些变更。

此外，请务必查看仅影响以 Android 14 为目标平台的应用的行为变更列表。

核心功能

默认拒绝设定精确的闹钟

Exact alarms are meant for user-intentioned notifications, or for actions that need to happen at a precise time. Starting in Android 14, the SCHEDULE_EXACT_ALARM permission is no longer being pre-granted to most newly installed apps targeting Android 13 and higher—the permission is denied by default.

Learn more about the changes to the permission for scheduling exact alarms.

当应用进入缓存时，上下文注册的广播将加入队列

On Android 14, the system can place context-registered broadcasts in a queue while the app is in the cached state. This is similar to the queuing behavior that Android 12 (API level 31) introduced for async binder transactions. Manifest-declared broadcasts aren't queued, and apps are removed from the cached state for broadcast delivery.

When the app leaves the cached state, such as returning to the foreground, the system delivers any queued broadcasts. Multiple instances of certain broadcasts might be merged into one broadcast. Depending on other factors, such as system health, apps might be removed from the cached state, and any previously queued broadcasts are delivered.

应用只能终止自己的后台进程

Starting in Android 14, when your app calls killBackgroundProcesses(), the API can kill only the background processes of your own app.

If you pass in the package name of another app, this method has no effect on that app's background processes, and the following message appears in Logcat:

Invalid packageName: com.example.anotherapp

Your app shouldn't use the killBackgroundProcesses() API or otherwise attempt to influence the process lifecycle of other apps, even on older OS versions. Android is designed to keep cached apps in the background and kill them automatically when the system needs memory. If your app kills other apps unnecessarily, it can reduce system performance and increase battery consumption by requiring full restarts of those apps later, which takes significantly more resources than resuming an existing cached app.

Note: It isn't possible for a 3rd-party application to improve the memory, power, or thermal behavior of an Android device. You should ensure that your app is compliant with Google Play's policy regarding misleading claims.

第一个请求 MTU 的 GATT 客户端的 MTU 设置为 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.

Note: This change doesn't have an impact unless the peripheral device isn't handling the MTU negotiation properly and accepting any MTU size even if it doesn't support it. In such cases, it could cause issues when your app sends large amounts of data from Android 14 devices.

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

将应用放入“受限待机”存储分区的新原因

Android 14 introduces a new reason an app can be placed into the restricted standby bucket. The app's jobs trigger ANR errors multiple times due to onStartJob, onStopJob, or onBind method timeouts. (See JobScheduler reinforces callback and network behavior for changes to onStartJob and onStopJob.)

Note: See power management to see how the app is impacted if it is placed into the restricted bucket. The app is moved back to the active bucket when the user launches the app to the foreground, just as in previous Android versions.

To track whether or not the app has entered the restricted standby bucket, we recommend logging with the API UsageStatsManager.getAppStandbyBucket() on job execution or UsageStatsManager.queryEventsForSelf() on app startup.

mlock 限制为 64 KB

In Android 14 (API level 34) and higher, the platform reduces the maximum memory that can be locked using mlock() to 64 KB per process. In previous versions, the limit was 64 MB per process. This restriction promotes better memory management across apps and the system. To provide more consistency across devices, Android 14 adds a new CTS test for the new mlock() limit on compatible devices.

系统会强制使用缓存的应用资源

从设计上讲，当应用的进程移至后台且没有任何其他应用进程组件在运行时，应用进程将处于缓存状态。此类应用进程可能会因系统内存压力而终止。在此状态下，Activity 实例在调用并返回 onStop() 方法后执行的任何工作均不可靠，强烈建议不要这样做。

Android 14 对此设计引入了一致性和强制执行要求。在应用进程进入缓存状态后不久，系统会禁止后台工作，直到进程组件重新进入生命周期的活跃状态。

使用框架支持的典型生命周期 API（例如服务、JobScheduler 和 Jetpack WorkManager）的应用应该不受这些变化的影响。

用户体验

关于不可关闭通知用户体验方式的变更

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

数据安全信息更显眼

To enhance user privacy, Android 14 increases the number of places where the system shows the information you have declared in the Play Console form. Currently, users can view this information in the Data safety section on your app's listing in Google Play.

We encourage you to review your app's location data sharing policies and take a moment to make any applicable updates to your app's Google Play Data safety section.

Learn more in the guide about how data safety information is more visible on Android 14.

无障碍功能

非线性字体放大至 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

最低可安装的目标 API 级别

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

媒体所有者软件包名称可能会隐去

The media store supports queries for the OWNER_PACKAGE_NAME column, which indicates the app that stored a particular media file. Starting in Android 14, this value is redacted unless at least one of the following conditions is true:

• The app that stored the media file has a package name that is always visible to other apps.

• The app that queries the media store requests the QUERY_ALL_PACKAGES permission.

  Caution: Use of the QUERY_ALL_PACKAGES permission is subject to Google Play Policy.

Learn more about how Android filters package visibility for privacy purposes.