请求后台任务在Android中多次运行

Question

I have a long running calculation that takes sensor data as arguments.

After getting the calculation result, I would like to call a method to update a view.

This calculation may take some time, therefore I'm unable to run it inside the Activity code as I receive sensor data because the UI thread freezes or slows down.

Since I want to run this calculation every time I receive new sensor data, what options Android offers me?

I've tried using AsyncTask . I would start an AsyncTask to run the calculation with new sensor data, and the View's update method would get called inside its onPostExecute .

Unfortunately this approach created issues with animation synchronization: an AsyncTask could finish after the next, and the View's update would get called with outdated information, effectively making its animations jittery.

I've also tried running the same AsyncTask with executeOnExecutor , passing a Single Thread Executor to it, but that didn't stop the animation jitter.

Lastly, I've tried to run an IntentService with a ResultReceiver callback inside the MainActivity. While I'm able to get it running, it only runs once. Have I misunderstood what IntentServices are for? I can't seem to run it multiple times (using a method that creates an intent with extra parameters and calls startService with it).

Summary : I have a slow method that operates on sensor data. I want to run it in background every time I get new sensor data, and use its result/response to update a View.

Any suggestions?

Answer 1

Though I am not sure what kind of animation you are using,depending upon the structure of your application and code, few of the options could be that rather than updating data in onPostExecute(),see if you can do it in callback method of animation which tells you that animation has finished,ie calculate it in asynctask but update your arraylist or whatever you use in callback method of animation . Secondly if you have a general idea of how much time animation takes to finish you can apply handler with timer and try to match both operations by calling the animation with delay. Similarly you can use broadcast receiver or interface if the UI operation is across the activities.

Answer 2

Your Service is here.....

public class One extends Service {
public static final long NOTIFY_INTERVAL = 10 * 1000;
private Handler handler = new Handler();
private Timer timer = null;

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

@Override
public void onCreate() 
{
    if (timer != null) 
    {
        timer.cancel();
    } else
    {
        timer = new Timer();
    }
    timer.scheduleAtFixedRate(new DisplayTime(), 0, NOTIFY_INTERVAL);
}

class DisplayTime extends TimerTask 
{

    @Override
    public void run() {
        handler.post(new Runnable() {

            @Override
            public void run() {
                recall();
                Toast.makeText(getApplicationContext(), "run", Toast.LENGTH_SHORT).show();
            }

        });
    } 
 public void recall() {

      // Write here Async Task Method......
    }
 }           
  @Override
  public void onDestroy()
  {
    super.onDestroy();
    Toast.makeText(getApplicationContext(), "des", Toast.LENGTH_SHORT).show();
  }
}

Answer 3

您可以实现AsyncTask onProgressUpdate()方法，然后在doInBackground()中调用publishProgress()您可以在onProgressUpdate()更新UI