android - LocationClient doesn't give callback when screen light goes off but my WakefulThread is running flawlessly as expected

Question

To retrieve fused location in background, I have created a library which is very similar to cwac-locpoll library created by Commonsguy.

Inside PollerThread , I am trying to connect, request and retrieve the locations using LocationClient.

I am able to get connected by receiving callback on onConnected method but I am not able to get callback on onLocationChanged method.so my onTimeout thread executes as per decided interval.

NOTE: This issue happens only when screen light goes off.otherwise it works completely fine.

I suspect there might be bug in new Location Api.

Here is the implementation of my PollerThread,

          private class PollerThread extends WakefulThread  implements GooglePlayServicesClient.ConnectionCallbacks,
      GooglePlayServicesClient.OnConnectionFailedListener,LocationListener{

            private static final String TAG = "PollerThread";

            //context
            private Context mContext=null;
            private LocationClient mLocationClient=null;
            private LocationRequest mLocationRequest=null;
            private LocationManager locMgr=null;
            private Intent intentTemplate=null;
            private Handler handler=new Handler();
            private Runnable onTimeout = new Runnable() {

            @Override
            public void run() {

            Log.e(TAG, "onTimeout");

            //prepare broadcast intent
              Intent toBroadcast=new Intent(intentTemplate);
              toBroadcast.putExtra(FusedPoller.EXTRA_ERROR, "Timeout!");
              toBroadcast.putExtra(
                      FusedPoller.EXTRA_ERROR_PROVIDER_DISABLED, false);
              toBroadcast.putExtra(FusedPoller.EXTRA_LASTKNOWN,
                      mLocationClient.getLastLocation());
              sendBroadcast(toBroadcast);

            //stop the thread
              quit();
            }
          };

        PollerThread(Context mContext,LocationRequest mLocationRequest,PowerManager.WakeLock lock, LocationManager locMgr,
                     Intent intentTemplate) {
          super(lock, "LocationPoller-PollerThread");

          Log.e(TAG, "PollerThread");

          this.mContext=mContext;
          this.mLocationRequest=mLocationRequest;
          this.locMgr=locMgr; 
          this.intentTemplate=intentTemplate;
        }


        @Override
        protected void onPreExecute() {
            super.onPreExecute();
              Log.e(TAG, "onPreExecute");

            //setup timeout
            setTimeoutAlarm();

            //initiate connection
            initiateConnection();
        }

        @Override
        protected void onPostExecute() {
          super.onPostExecute();
          Log.e(TAG, "onPostExecute");

          //remove timeout
          removeTimeoutAlarm();
          //disconnect
          initiateDisconnection();
        }

        /**
         * Called when the WakeLock is completely unlocked.
         * Stops the service, so everything shuts down.
         */
        @Override
        protected void onUnlocked() {
            Log.e(TAG, "onUnlocked");
            stopSelf();
        }


        private void setTimeoutAlarm() {
            Log.e(TAG, "setTimeoutAlarm");
            handler.postDelayed(onTimeout, FusedLocationUtils.DEFAULT_TIMEOUT);
        }

        private void removeTimeoutAlarm()
        {
            Log.e(TAG, "removeTimeoutAlarm");
            handler.removeCallbacks(onTimeout);
        }

        private void initiateConnection()
        {
            Log.e(TAG, "initiateConnection");
            mLocationClient = new LocationClient(this.mContext, this, this);
            mLocationClient.connect();
        }

        private void initiateDisconnection()
        {
            Log.e(TAG, "initiateDisconnection");
            if(mLocationClient.isConnected())
            {
                mLocationClient.disconnect();
            }
        }


        @Override
        public void onConnected(Bundle arg0) {
            Log.e(TAG, "onConnected");


            Log.e(TAG, "provider: GPS-"+locMgr.isProviderEnabled(LocationManager.GPS_PROVIDER)+" NETWORK-"+locMgr.isProviderEnabled(LocationManager.NETWORK_PROVIDER));

                if (!(locMgr.isProviderEnabled(LocationManager.GPS_PROVIDER)) && !(locMgr.isProviderEnabled(LocationManager.NETWORK_PROVIDER))) {
                    Log.e(TAG, "both disabled");

                    //get last location and broadcast it
                    getLastLocationAndBroadcast();

                    //stop the thread
                    quit();
                }
                else
                {
                    Log.e(TAG, "provider enabled");

                    //get latest location and broadcast it
                    getLatestLocationAndBroadcast();
                    //don't quit from here,quit from onLocationChanged
                }

        }


        @Override
        public void onDisconnected() {
            Log.e(TAG, "onDisconnected");
            // TODO Auto-generated method stub

        }

        @Override
        public void onConnectionFailed(ConnectionResult arg0) {
            Log.e(TAG, "onConnectionFailed");
            // TODO Auto-generated method stub

        }
        @Override
        public void onLocationChanged(Location location) {


            Log.e(TAG, "onLocationChanged");

            //prepare broadcast intent
            Intent toBroadcast=new Intent(intentTemplate);
            toBroadcast.putExtra(FusedPoller.EXTRA_LOCATION, location);
            sendBroadcast(toBroadcast);

            //stop further updates
            stopUpdates();
            //stop the thread
            quit();

        }

        private void getLatestLocationAndBroadcast() {
            Log.e(TAG, "getLatestLocationAndBroadcast");
            if(mLocationClient.isConnected() && servicesConnected())
            {
                Log.e(TAG, "going to request updates");
                Log.e(TAG, "lockStatic.isHeld(): "+lockStatic.isHeld());
                mLocationClient.requestLocationUpdates(mLocationRequest, this);
            }
            else
            {
                Log.e(TAG, "not going to request updates");
            }
        }


        private void stopUpdates() {
            Log.e(TAG, "stopUpdates");
            if(servicesConnected())
            {
                Log.e(TAG,getString(R.string.location_updates_stopped));
                mLocationClient.removeLocationUpdates(this);
            }
            else
            {
                Log.e(TAG,"can't do:"+getString(R.string.location_updates_stopped));
            }
        }



        private void getLastLocationAndBroadcast() {
            Log.e(TAG, "getLastLocationAndBroadcast");
            if(mLocationClient.isConnected() && servicesConnected())
            {
                Log.e(TAG, "going to get last location: "+mLocationClient.getLastLocation());

                Intent toBroadcast = new Intent(intentTemplate);
                toBroadcast.putExtra(FusedPoller.EXTRA_ERROR,
                        "Location Provider disabled!");
                toBroadcast.putExtra(
                        FusedPoller.EXTRA_ERROR_PROVIDER_DISABLED, true);
                toBroadcast.putExtra(FusedPoller.EXTRA_LASTKNOWN,
                        mLocationClient.getLastLocation());
                sendBroadcast(toBroadcast);
            }
            else
            {
                Log.e(TAG, "not going to get last location");
            }
        }
      }

and servicesConnected method implementation,

            /**
         * Verify that Google Play services is available before making a request.
         *
         * @return true if Google Play services is available, otherwise false
         */
        private boolean servicesConnected() {

              Log.e(TAG, "servicesConnected");

            // Check that Google Play services is available
            int resultCode =
                    GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);

            // If Google Play services is available
            if (ConnectionResult.SUCCESS == resultCode) {
                // In debug mode, log the status
                Log.d(FusedLocationUtils.APPTAG, getString(R.string.play_services_available));

                // Continue
                return true;
            // Google Play services was not available for some reason
            } else {
                // Display an error dialog
                Log.d(FusedLocationUtils.APPTAG, getString(R.string.play_services_unavailable));
                Toast.makeText(this, getString(R.string.play_services_unavailable), Toast.LENGTH_SHORT).show();

                return false;
            }
        }

Answer 1

If you want to listen to frequent location updates in the background (e.g., every second), you should be running your code inside a Service:

http://developer.android.com/reference/android/app/Service.html

Activities can be ended by the Android platform at any point in time in which they are not in the foreground.

When using a Service, I would recommend having the Service implement the LocationListener directly, and not a Thread inside the Service. For example, use:

public class LocListener extends Service implements com.google.android.gms.location.LocationListener, ...{

I've used this design of implementing the LocationListener directly on the Service with the LocationClient and fused location provider in my GPS Benchmark app and I can confirm that this works even when the screen is off and the app is running in the background.

If you want to listen to occasional location updates in the background (e.g., every minute) using the fused location provider, a better design is to use PendingIntents, using the LocationClient.requestLocationUpdates(Location Request, PendingIntent callbackIntent) method:

https://developer.android.com/reference/com/google/android/gms/location/LocationClient.html#requestLocationUpdates(com.google.android.gms.location.LocationRequest,%20android.app.PendingIntent)

From the above Android doc:

This method is suited for the background use cases, more specifically for receiving location updates, even when the app has been killed by the system. In order to do so, use a PendingIntent for a started service. For foreground use cases, the LocationListener version of the method is recommended, see requestLocationUpdates(LocationRequest, LocationListener).

Any previous LocationRequests registered on this PendingIntent will be replaced.

Location updates are sent with a key of KEY_LOCATION_CHANGED and a Location value on the intent.

See the Activity Recognition example for a more detailed description of using PendingIntents to get updates while running in the background:

https://developer.android.com/training/location/activity-recognition.html

Modified excerpts from this documentation are below, changed by me to be specific to location updates.

First declare the Intent:

public class MainActivity extends FragmentActivity implements
        ConnectionCallbacks, OnConnectionFailedListener {
    ...
    ...
    /*
     * Store the PendingIntent used to send location updates
     * back to the app
     */
    private PendingIntent mLocationPendingIntent;
    // Store the current location client
    private LocationClient mLocationClient;
    ...
}

Request updates as you currently are, but this time pass in the pending intent:

/*
 * Create the PendingIntent that Location Services uses
 * to send location updates back to this app.
 */
Intent intent = new Intent(
        mContext, LocationIntentService.class);

...
//Set up LocationRequest with desired parameter here
...
/*
 * Request a PendingIntent that starts the IntentService.
 */
mLocationPendingIntent =
        PendingIntent.getService(mContext, 0, intent,
        PendingIntent.FLAG_UPDATE_CURRENT);
/*
 * Request location updates
 */
mLocationClient.requestLocationUpdates(mLocationRequest, callbackIntent);

Handle Location Updates

To handle the Intent that Location Services sends for each update interval, define an IntentService and its required method onHandleIntent(). Location Services sends out ... updates as Intent objects, using the the PendingIntent you provided when you called requestLocationUpdates(). Since you provided an explicit intent for the PendingIntent, the only component that receives the intent is the IntentService you're defining.

Define the class and the required method onHandleIntent():

/**
 * Service that receives Location updates. It receives
 * updates in the background, even if the main Activity is not visible.
 */
public class LocationIntentService extends IntentService {
    ...
    /**
     * Called when a new location update is available.
     */
    @Override
    protected void onHandleIntent(Intent intent) {
        Bundle b = intent.getExtras();
        Location loc = (Location) b.get(LocationClient.KEY_LOCATION_CHANGED);
        Log.d(TAG, "Updated location: " + loc.toString());


    }
    ...
}

IMPORTANT - to be as efficient as possible, your code in onHandleIntent() should return as quickly as possible to allow the IntentService to shut down. From IntentService docs:

http://developer.android.com/reference/android/app/IntentService.html#onHandleIntent(android.content.Intent)

This method is invoked on the worker thread with a request to process. Only one Intent is processed at a time, but the processing happens on a worker thread that runs independently from other application logic. So, if this code takes a long time, it will hold up other requests to the same IntentService, but it will not hold up anything else. When all requests have been handled, the IntentService stops itself, so you should not call stopSelf().

My understanding of the IntentService design is that you can spawn Threads inside onHandleIntent() to avoid blocking other location updates via platform calls to onHandleIntent(), just be aware that the Service will continue to run until all the running threads terminate.