Android Jobservice 被销毁

Question

我建立了一个 Jobservice 来做一些事情。出于测试目的，我让它每三十秒运行一次。为了找到问题，我将服务减少到什么都不做(!)。我知道，系统可以停止工作；如果 onStopJob 方法返回 true 它将重新启动。这种情况会发生并且效果很好，虽然我想知道发生的频率和时间(在半夜，手机刚好放在 table 上!)。
为了检查所有这些，我正在使用 SharedPreferences，跟踪停止和重新启动。
然而，我发现，这项工作不仅停止了，而且有时甚至被完全摧毁了。然后我在 OnDestroy 方法中设置了一个重启例程。这是行不通的。作业正在重新启动，但立即又被销毁了。所以我有一些问题:
为什么它首先被销毁？
为什么不能重新启动它？
我该怎么做才能让它更稳定？
在 Android 5.0.1 下的 Galaxy S4 和 6.0 下的 XPeria Z2 上试用
针对 MinSDK 5.0、TargetSDK 6.0 编译。
这是我的 JobSchedulerService 的代码:

public class  JobSchedulerService extends JobService implements
    DataApi.DataListener,
    GoogleApiClient.ConnectionCallbacks,
    GoogleApiClient.OnConnectionFailedListener 
{

private boolean stoppedByUser = false;
public DateFormat formatter;
String stoptimeText;
public GregorianCalendar apptTime;
public Context myCnt;

@Override
public boolean onStartJob(JobParameters params){
        doJob(this);
        jobFinished(params, false );
    return true;
}

public void doJob(Context context){
    myCnt = context;
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(myCnt);
    SharedPreferences.Editor editor = prefs.edit();
    stoptimeText = prefs.getString("stopped","not yet stopped");
    editor.putString("started", "Job was running at " + timeNow());
    editor.apply();
    // do something here
}

@Override
public boolean onStopJob(JobParameters params){
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
    stoppedByUser = prefs.getBoolean("stoppedByUser", false);
    SharedPreferences.Editor editor = prefs.edit();
    stoptimeText += "Job stopped autom. at " + timeNow();
    editor.putString("stopped", stoptimeText);
    editor.apply();
    if (stoppedByUser){
        stoppedByUser = false;
        editor.putBoolean("stoppedByUser", false);
        stoptimeText += "OnStopJob called by user-stop at " + timeNow();
        editor.putString("stopped", stoptimeText);
        editor.apply();
        return false;
    }
    else return true;
}

@Override
public void onDestroy() {
    super.onDestroy();
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
    stoppedByUser = prefs.getBoolean("stoppedByUser", false);
    SharedPreferences.Editor editor = prefs.edit();
    stoptimeText += "Job was destroyed at "+ timeNow();
    editor.putString("stopped", stoptimeText);
    editor.apply();
    if (!stoppedByUser){
        JobInfo.Builder builder = new JobInfo.Builder(1,
                new ComponentName(getPackageName(), JobSchedulerService.class.getName()));
        builder.setPeriodic(30 * 1000);
        builder.setPersisted(true);
        stoptimeText += "Job rest. after dstr. at " + timeNow();
        editor.putString("stopped", stoptimeText);
        editor.putString("started", "Auto update started after destroy! Check if really running!");
        editor.apply();
    }
    else {
        stoptimeText += "OnDestroy called by user-stop at " + timeNow();
        editor.putString("stopped", stoptimeText);
        editor.apply();
    }
}

public String timeNow(){
    apptTime = (GregorianCalendar) GregorianCalendar.getInstance(TimeZone.getTimeZone("UTC"));
    formatter = new SimpleDateFormat("EEE, dd./HH:mm", Locale.ENGLISH);
    formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
    return formatter.format(apptTime.getTimeInMillis());
}

@Override
public void onDataChanged(DataEventBuffer dataEvents) {
}

@Override
public void onConnected(Bundle connectionHint) {
}

@Override
public void onConnectionFailed(ConnectionResult arg0) {
}

@Override
public void onConnectionSuspended(int arg0) {
}
}

这是我的 MainActivity(缩写):

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    myCnt = this;

    initGoogleApiClient();

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    viewPager = (ViewPager) findViewById(R.id.viewpager);
    setupViewPager(viewPager);

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    if (tabLayout != null)
        tabLayout.setupWithViewPager(viewPager);

    mJobScheduler = (JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);

//.......

public void startJob(){
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
    SharedPreferences.Editor editor = prefs.edit();
    editor.putString("started", "auto updates started by user!");
    editor.putBoolean("stoppedByUser", false);
    editor.apply();

    JobSchedulerService jss = new JobSchedulerService(); // used to "first run" the job, so there is no waiting time for the user
    jss.doJob(myCnt);

    JobInfo.Builder builder = new JobInfo.Builder(1,
            new ComponentName(getPackageName(), JobSchedulerService.class.getName()));
    builder.setPeriodic(30 * 1000);
    builder.setPersisted(true);

    if (mJobScheduler.schedule(builder.build()) <= 0) {
        Toast.makeText(MainActivity.this, "Failure starting Jobservice!", Toast.LENGTH_LONG).show();
    }
}

Answer 1

经过长时间的研究，我发现以下是问题所在:在我的

// do something here  

我有一个异步任务。但是，根据 Google 的说法，这仅适用于 UI 线程(请参阅:https://developer.android.com/reference/android/os/AsyncTask.html)。
在我的 JobSchedulerService 中使用它导致它在一段时间后被销毁。
我现在使用(常规)单独的线程在服务中“做某事”，并且它有效。