Android:在服务中启动一个线程

Question

我想在我自己的服务中启动一个从 Activity 启动的新线程。在这个线程中，我想每 3 秒更新一次数据库中的数据。我创建了数据库并在我的 onStartCommand() 方法中对其进行了初始化。我应该在哪里实现我的线程以及如何实现？

我试过了，但没有用，不幸的是，该应用程序将被关闭。如果不调用此方法，一切正常。

我创建了这个方法，我在我的 onStartCommand 中调用了它

private void startThreadUpdatingDatabase(){
    Log.d("Database", "startThreadUpdatingDatabase(was called)");
    new Thread(new Runnable() { 
        public void run(){
            //do stuff
        }
    }).start();
}

Answer 1

如果你想开始一个循环任务，你可以尝试不同的方法:

1)报警
2)处理程序
3) TimerTask(我最不喜欢的)

报警:

private AlarmManager mAlarmManager;
private static final long ALARM_INTERVAL = 3 * 60 * 1000;

private void issueAlarm() {
    if(mAlarmManager == null)
        mAlarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
    Calendar calendar = Calendar.getInstance(Locale.US);
    calendar.add(Calendar.MILLISECOND, (int) ALARM_INTERVAL);
    Intent intent = new Intent(this, AlarmBroadcastReceiver.class);
    alarmIntent = PendingIntent.getBroadcast(this, ALARM_REQUEST_CODE, intent, 0);
    mAlarmManager.setRepeating(AlarmManager.RTC, calendar.getTimeInMillis(), ALARM_INTERVAL, alarmIntent);
}

创建您的 AlarmReceiver:

public class AlarmBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        //Do DB Stuff here
    }

}

并且不要忘记在 list 中注册它:

<receiver
    android:name=".AlarmBroadcastReceiver"
    android:exported="false" />

处理程序:

@Override
public void onCreate() {
    // Start up the thread running the service.  Note that we create a
    // separate thread because the service normally runs in the process's
    // main thread, which we don't want to block.  We also make it
    // background priority so CPU-intensive work will not disrupt our UI.
    HandlerThread thread = new HandlerThread("ServiceStartArguments",
        Process.THREAD_PRIORITY_BACKGROUND);
    thread.start();

    // Get the HandlerThread's Looper and use it for our Handler
    mServiceLooper = thread.getLooper();
    mServiceHandler = new ServiceHandler(mServiceLooper);
}

然后排队你发布的任务

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    //As danny117 pointed out, multiple clients starting the service
    //Can trigger this.
    mServiceHandler.removeCallbacks(yourRunnable);
    mServiceHandler.post(yourRunnable);
    return super.onStartCommand(intent, flags, startId);
}

可运行的应该是这样的:

private Runnable yourRunnable = new Runnable() {
        @Override
        public void run(){
        //DB work here
        if(mServiceHandler != null)
            mServiceHandler.postDelayed(this, ALARM_INTERVAL);
        }
}

在服务停止后也进行清理:

@Override
public void onDestroy() {
    super.onDestroy();
    mServiceHandler.removeCallbacks(yourRunnable);
    mServiceLooper.quit();
}

计时器:

创建你的计时器:

private Timer myTimer = new Timer();

创建循环计时器任务:

private void scheduleTask() {
    myTimer.scheduleAtFixedRate(new TimerTask() {
        public void run() {
            //Do DB stuff here
        }
    }, 0, ALARM_INTERVAL);
}

引用资料:
Scheduling Repeating Alarms
Creating a Service