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我正在写一篇关于 JobScheduler 的教程，但我发现了一个奇怪的行为。我要求在 1 秒内安排 3 个不同的作业（.setOverrideDeadline(1000)），但它们都被提交并运行了两次......所以这里的代码：

public class MyApplication extends Application {
    private static final int JOB_ID_HanlderThread = 100;
    private static final int JOB_ID_ExecutorService = 200;
    private static final int JOB_ID_AsyncTask = 300;
    JobScheduler mJobScheduler;
    ExecutorService myExecutorServiceForJobs=null;
    private static MyApplication INSTANCE;
    public static MyApplication getInstance(){
        return INSTANCE;
    }


    /**
     * Called when the application is starting, before any activity, service,
     * or receiver objects (excluding content providers) have been created.
     * Implementations should be as quick as possible (for example using
     * lazy initialization of state) since the time spent in this function
     * directly impacts the performance of starting the first activity,
     * service, or receiver in a process.
     * If you override this method, be sure to call super.onCreate().
     */
    @Override
    public void onCreate() {
        Log.e("MyApplication", "*********************** onCreate *****************************");
        super.onCreate();
        //use only for the ExceutorService case
        INSTANCE=this;
        //instanciate your JobScheduler
        mJobScheduler= (JobScheduler) getSystemService(JOB_SCHEDULER_SERVICE);
        Log.e("MyApplication", "onCreate: JobScheduler instanciate");

        //this first example use the HandlerThread (no need of executor service)
        //---------------------------------------------------------------------
        //define your JobServices here
        JobInfo.Builder builder = new JobInfo.Builder(JOB_ID_HanlderThread,
                new ComponentName( getPackageName(),
                        MyJobServiceUsingHandlerThread.class.getName() ) );
        //begin in one second
        builder.setOverrideDeadline(1000);
        int returnedValue;
        //the return value is failure(0) or success(1) not the JobId if success (Javadoc wrong)
        returnedValue=mJobScheduler.schedule( builder.build() );
        //launch it
        if( returnedValue <= 0 ) {
            //If something goes wrong (manage exception/error is better than logging them)
            Log.e("MyApplication", "onCreate: JobScheduler launch the task failure");
        }else{
            //nothing goes wrong
            Log.e("MyApplication", "onCreate: JobScheduler launch the task suceess JOB_ID_HanlderThread "+returnedValue);
        }

        //this second example use ExecutorService
        //---------------------------------------
        //then again define your Job and launch it
        JobInfo.Builder builder1 = new JobInfo.Builder(JOB_ID_ExecutorService,
                new ComponentName( getPackageName(),
                        MyJobServiceUsingExecutor.class.getName() ) );
        //begin in one second
        builder1.setOverrideDeadline(1000);
        //launch it
        returnedValue=mJobScheduler.schedule( builder1.build() );
        if( returnedValue <= 0 ) {
            //If something goes wrong (manage exception/error is better than logging them)
            Log.e("MyApplication", "onCreate: JobScheduler launch the task failure");
        }else{
            //nothing goes wrong
            Log.e("MyApplication", "onCreate: JobScheduler launch the task suceess JOB_ID_ExecutorService "+returnedValue);
        }

        //this third example use AsyncTask
        //--------------------------------
        //then again define your Job and launch it
        JobInfo.Builder builder2 = new JobInfo.Builder(JOB_ID_AsyncTask,
                new ComponentName( getPackageName(),
                        MyJobServiceUsingAsyncTask.class.getName() ) );
        //begin in one second
        builder2.setOverrideDeadline(1000);
        //launch it
        returnedValue=mJobScheduler.schedule( builder2.build() );
        if( returnedValue <= 0 ) {
            //If something goes wrong (manage exception/error is better than logging them)
            Log.e("MyApplication", "onCreate: JobScheduler launch the task failure");
        }else{
            //nothing goes wrong
            Log.e("MyApplication", "onCreate: JobScheduler launch the task suceess JOB_ID_AsyncTask "+returnedValue);
        }
    }

使用此代码，我希望我的作业运行一次，但如果我查看我获得的日志： 

10-20 06:45:13.118 13041-13041/? E/MyApplication: *********************** onCreate *****************************
10-20 06:45:13.122 13041-13041/? E/MyApplication: onCreate: JobScheduler instanciate
10-20 06:45:13.126 13041-13041/? E/MyApplication: onCreate: JobScheduler launch the task suceess JOB_ID_HanlderThread 1
10-20 06:45:13.127 13041-13041/? E/MyApplication: onCreate: JobScheduler launch the task suceess JOB_ID_ExecutorService 1
10-20 06:45:13.130 13041-13041/? E/MyApplication: onCreate: JobScheduler launch the task suceess JOB_ID_AsyncTask 1
10-20 06:45:13.559 13041-13041/? E/MyJobServiceHandler: onStartJob called <--------------------------------
10-20 06:45:13.572 13041-13041/? E/MyJobServiceExecutor: onStartJob called <--------------------------------
10-20 06:45:14.133 13041-13041/? E/MyJobServiceAsync: onStartJob called <--------------------------------
10-20 06:45:14.141 13041-13041/? E/MyJobServiceAsync: onStartJob called <--------------------------------
10-20 06:45:18.571 13041-13066/? E/MyHandler: The work is done in a separate thread called MyJobServiceUsingHandlerThread
10-20 06:45:18.573 13041-13041/? E/MyJobServiceHandler: onDestroy called, Looper is dead  <******************************************
10-20 06:45:18.574 13041-13041/? E/MyJobServiceHandler: onStartJob called <--------------------------------
10-20 06:45:18.576 13041-13067/? E/MyRunnable: The work is done in a separate thread called MyJobServiceUsingExecutorService
10-20 06:45:18.577 13041-13041/? E/MyJobServiceExecutor: onDestroy called, executor service is dead  <******************************************
10-20 06:45:18.577 13041-13041/? E/MyApplication: killMyExecutorServiceForJob called
10-20 06:45:18.577 13041-13041/? E/MyApplication: myExecutorServiceForJobs isShutDown
10-20 06:45:18.580 13041-13041/? E/MyJobServiceExecutor: onStartJob called <--------------------------------
10-20 06:45:19.145 13041-13070/? E/MyAsyncTask: The work is done in a separate thread called AsyncTask #1
10-20 06:45:19.145 13041-13041/? E/MyAsyncTask: The work is finished  <******************************************
10-20 06:45:23.576 13041-13075/? E/MyHandler: The work is done in a separate thread called MyJobServiceUsingHandlerThread
10-20 06:45:23.577 13041-13041/? E/MyJobServiceHandler: onDestroy called, Looper is dead  <******************************************
10-20 06:45:23.582 13041-13076/? E/MyRunnable: The work is done in a separate thread called MyJobServiceUsingExecutorService
10-20 06:45:23.584 13041-13041/? E/MyJobServiceExecutor: onDestroy called, executor service is dead  <******************************************
10-20 06:45:23.584 13041-13041/? E/MyApplication: killMyExecutorServiceForJob called
10-20 06:45:23.584 13041-13041/? E/MyApplication: myExecutorServiceForJobs isShutDown
10-20 06:45:24.147 13041-13077/? E/MyAsyncTask: The work is done in a separate thread called AsyncTask #2
10-20 06:45:24.148 13041-13041/? E/MyAsyncTask: The work is finished  <******************************************

我在本教程中所做的是使用 HandlerThread 运行一个作业，另一个使用 ExecutorService 运行，最后一个使用 AsyncTask 来解释如何在后台线程中完成工作。我展示了这种不同的技术，因为在某些用例中，您可能希望将作业排入同一线程 (HandlerThread) 或管理线程池 (ExecutorService) 或仅使用非托管线程 (AsyncTask)。

我定义了这些作业并在 MyApplication:onCreate 方法中安排它们。为了更深入地了解代码，我把它放在 GitHub 上：https ://github.com/MathiasSeguy-Android2EE/JobSchedulerForGitHub

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1 回答 1

23

谢谢你 - 我在 JobScheduler 上工作。根据您的应用程序（谢谢！）我设法很容易地重现了这个并追踪了错误的原因。

tl;博士，这种情况在教程应用程序之外不会经常发生。要在您的教程中解决它，请将您的作业的截止日期增加到大于每个后台线程运行的时间量。

正在发生的事情是您连续安排您的作业，并且 JobScheduler 几乎可以立即按照它们的安排运行它们。然而，一秒钟后（对于“真正的”应用程序来说，一秒钟不会发生的部分）覆盖期限警报触发，并且作业调度程序非常积极地决定任何期限已过期的作业都需要再次运行（API合同规定“最后期限到期”胜过所有其他考虑），因此它将其放入待处理队列中。一旦执行作业完成，就会检查待处理队列，并且那里有一个作业，所以它运行。

因此，如果在作业运行时截止日期到期，则作业将触发 2 次。确保截止日期在作业运行之前（导致作业运行）或之后（警报实际上不会让 b/c 作业已经完成）到期，并且一切都按预期工作。

我已经在 Android N 中修复了这个问题（不幸的是 M 已经发布了），并添加了一个 CTS 测试以确保它保持修复。感谢您提请我们注意

于 2015-10-23T00:42:28.757 回答