关于Android中的PollingService定时轮询任务的讲解

class PollingThread extends Thread {
        @Override
        public void run() {
            Log.i("zzf", "Polling...");
        }
    }

public class PollingReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub
        Log.i("zzf", "Receive!");
        Intent i = new Intent(context, PollingService.class);
        context.startService(i);
    }

}

public class PollingService extends Service {

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // TODO Auto-generated method stub
        //创建PollingThread子线程，用于执行任务
        new PollingThread().start();
        // 获取AlarmManager系统服务
        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        // 包装需要执行Service的Intent
        Intent i = new Intent(this, PollingReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, i, 0);
        int anSeconds = 5 * 1000; // 5秒
        //  触发时间
        long triggerAtTime = SystemClock.elapsedRealtime() + anSeconds;
        manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtTime, pendingIntent);
        return super.onStartCommand(i, flags, startId);
    }        

　　　　 Log.i("zzf","Start polling service...");
        Intent intent = new Intent(this, PollingService.class);
        startService(intent);