将前台服务迁移到用户发起的数据传输作业

Android 14 applies strict rules on when apps are allowed to use foreground services.

Also in Android 14 we are introducing a new API to specify that a job must be a user-initiated data transfer job. This API is helpful for use cases that require longer-duration, user-initiated transferring of data, such as downloading a file from a remote server. These types of tasks should use a user-initiated data transfer job.

User-initiated data transfer jobs are started by the user. These jobs require a notification, start immediately, and may be able to run for an extended period of time as system conditions allow. You can run several user-initiated data transfer jobs concurrently.

User initiated jobs must be scheduled while the application is visible to the user (or in one of the allowed conditions). After all constraints are met, user initiated jobs can be executed by the OS, subject to system health restrictions. The system may also use the provided estimated payload size to determine how long the job executes.

Note: If you're currently using WorkManager for network data transfer use cases, we recommend that you continue using that library instead of user-initiated data transfer jobs.

用户发起的数据传输作业的权限

由用户发起的数据传输作业需要具备以下新权限才能运行：RUN_USER_INITIATED_JOBS。系统会自动授予此权限。如果您未在应用清单中声明此权限，系统会抛出 SecurityException。

安排用户发起的数据传输作业的流程

如需运行用户发起的作业，请执行以下操作：

1. 如果这是您第一次使用 JobScheduler 声明 API，请在清单中声明 JobService 和相关权限。此外，还要为数据传输定义 JobService 的具体子类：

   <service android:name="com.example.app.CustomTransferService"
           android:permission="android.permission.BIND_JOB_SERVICE"
           android:exported="false">
           ...
   </service>
   

   class CustomTransferService : JobService() {
     ...
   }
   

2. 在清单中声明 RUN_USER_INITIATED_JOBS 权限：

   <manifest ...>
       <uses-permission android:name="android.permission.RUN_USER_INITIATED_JOBS" />
       <application ...>
           ...
       </application>
   </manifest>
   

3. 构建 JobInfo 对象时，调用新的 setUserInitiated() 方法。我们还建议您在创建作业时通过调用 setEstimatedNetworkBytes() 提供载荷大小估算值：

   val networkRequestBuilder = NetworkRequest.Builder()
           .addCapability(NET_CAPABILITY_INTERNET)
           .addCapability(NET_CAPABILITY_NOT_METERED)
           // Add or remove capabilities based on your requirements
           .build()
   
   val jobInfo = JobInfo.Builder()
           // ...
           .setUserInitiated(true)
           .setRequiredNetwork(networkRequestBuilder.build())
           .setEstimatedNetworkBytes(1024 * 1024 * 1024)
           // ...
           .build()
   

4. 在应用可见或在允许的条件列表中，作业应在转移开始前调度：

   val jobScheduler: JobScheduler =
       context.getSystemService(Context.JOB_SCHEDULER_SERVICE) as JobScheduler
   jobScheduler.schedule(jobInfo)
   

5. 执行作业时，请确保对 JobService 对象调用 setNotification()。该值用于在任务管理器和状态栏通知区域中告知用户作业正在运行：

   class CustomTransferService : JobService() {
     override fun onStartJob(params: JobParameters?): Boolean {
         val notification = Notification.Builder(applicationContext, NOTIFICATION_CHANNEL_ID)
                 .setContentTitle("My user-initiated data transfer job")
                 .setSmallIcon(android.R.mipmap.myicon)
                 .setContentText("Job is running")
                 .build()
   
         setNotification(params, notification.id, notification,
                 JobService.JOB_END_NOTIFICATION_POLICY_DETACH)
         // Do the job execution.
     }
   }
   

   注意： 如果您未在短时间内调用 setNotification()，则会导致应用出现 ANR。

6. 定期更新通知，让用户了解作业的状态和进度。如果您在安排作业之前无法确定传输大小，或者需要更新估算的传输大小，请在已知传输大小后使用新的 API updateEstimatedNetworkBytes() 更新传输大小。

7. 执行完成后，调用 jobFinished() 以向系统表明作业已完成，或者应重新调度作业。

可以停止用户发起的数据传输作业

用户和系统都可以停止用户发起的传输作业。

由用户从任务管理器提供

用户可以停止显示在任务管理器中的用户发起的传输作业。

在用户按 Stop 时，系统会执行以下操作：

• 立即终止应用的进程，包括正在运行的所有其他作业或前台服务。
• 不针对任何正在运行的作业调用 onStopJob()。
• 阻止重新调度用户可见的作业。

因此，建议在发布的作业通知中提供控件，以便顺利停止和重新调度作业。

请注意，在特殊情况下，Stop 按钮不会显示在任务管理器中的作业旁边，或者该作业根本不会显示在任务管理器中。

由系统提供

Unlike regular jobs, user-initiated data transfer jobs are unaffected by App Standby Buckets quotas. However, the system still stops the job if any of the following conditions occur:

• A developer-defined constraint is no longer met.
• The system determines that the job has run for longer than necessary to complete the data transfer task.
• The system needs to prioritize system health and stop jobs due to increased thermal state.
• The app process is killed due to low device memory.

When the job is stopped by the system (not by the low-memory case), the system calls onStopJob(), and the system retries the job at a time that the system deems to be optimal. Check that your app can persist data transfer state, even if onStopJob() isn't called, and that your app can restore this state when onStartJob() is called again.

允许安排用户发起的数据传输作业的条件

Apps can only start a user-initiated data transfer job if the app is in the visible window, or if the certain conditions are met. To determine when a user-initiated data transfer job can be scheduled, the system applies the same list of conditions that allow apps to start an activity from the background in special cases. Notably, this list of conditions are not the same as the set of exemptions for background-started foreground service restrictions.

The exceptions to the previous statement are the following:

• If an app can launch activities from the background, they can also launch user-initiated data transfer jobs from the background.
• If an app has an activity in the back stack of an existing task on the Recents screen, that alone doesn't allow a user-initiated data transfer job to run.

If the job is scheduled at some other time not listed in the allowed conditions list, the job fails and returns a RESULT_FAILURE error code.

适用于用户发起的数据传输作业的约束条件

为了支持在最佳时间点运行的作业，Android 提供了为每种作业类型分配约束条件的功能。这些约束条件从 Android 13 开始就已经可用。

注意：下表仅比较了因作业类型而异的约束条件。如需了解所有约束条件，请参阅 JobScheduler 开发者页面或工作约束条件。

下表显示了支持给定作业约束条件的不同作业类型，以及 WorkManager 支持的作业约束条件集。您可以使用表格前的搜索栏按作业约束方法的名称过滤表格。

以下是用户发起的数据传输作业允许使用的约束条件：

• setBackoffCriteria(JobInfo.BACKOFF_POLICY_EXPONENTIAL)
• setClipData()
• setEstimatedNetworkBytes()
• setMinimumNetworkChunkBytes()
• setPersisted()
• setNamespace()
• setRequiredNetwork()
• setRequiredNetworkType()
• setRequiresBatteryNotLow()
• setRequiresCharging()
• setRequiresStorageNotLow()

测试

下面列出了有关如何手动测试应用作业的一些步骤：

• 如需获取作业 ID，请获取在构建作业时定义的值。

• 如需立即运行作业或重试已停止的作业，请在终端窗口中运行以下命令：

  adb shell cmd jobscheduler run -f APP_PACKAGE_NAME JOB_ID
  

• 如需模拟系统强行停止作业（由于系统运行状况或超出配额条件），请在终端窗口中运行以下命令：

  adb shell cmd jobscheduler timeout TEST_APP_PACKAGE TEST_JOB_ID