Search code examples
androidmultithreadinghandlerlooper

How to manage Loopers and Threads (thread doesn't die anymore!)


I created a class extending Thread to retrieve user location through LocationManager in a non-ui thread. I implemented this as a thread because it has to be started on request and do its work just for a limited time. By the way, I had to add a Looper object in the thread, to be able to create the handler for the LocationManager (onLocationChanged).

This is the code:

public class UserLocationThread extends Thread implements LocationListener {
//...
public void run() {
    try {
        Looper.prepare();
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
        Looper.loop();
        Looper.myLooper().quit();
    } catch (Exception e) {
        //...
    }
}

@Override
public void onLocationChanged(Location location) {
    locationManager.removeUpdates(this);
    //...
    handler.sendMessage(msg); //this is the handler for communication with father thread
}

//...}

I would like the thread to start, receive the user location data (in this case just one time), send the data to the main thread via a message to the handler, and then die. The problem is that in my case the thread does not die anymore, once the run method ended (that should be fine, because otherwise onLocationChanged would not receive the new locations).

But in this way, assuming that thread's stop and suspend methods are deprecated, what would be a good way, in this case at least, to make a thread with a looper die?

Thanks in advance ;)


Solution

  • You can explicitly quit from Looper's loop using Handler:

    private Handler mUserLocationHandler = null;
    private Handler handler = null;
    
    public class UserLocationThread extends Thread implements LocationListener {    
    
     public void run() {
        try {
              Looper.prepare();
            mUserLocationHandler = new Handler();
            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
            Looper.loop();
    
        } catch (Exception e) {
            //...
        }
    }
    
    
    @Override
    public void onLocationChanged(Location location) {
        locationManager.removeUpdates(this);
        //...
        handler.sendMessage(msg); 
        if(mUserLocationHandler != null){
            mUserLocationHandler.getLooper().quit();
        }
    }