How To Get Location Using AsyncTask

Question

I am pulling my hair out with trying to find a good solution to this problem. I made my app so it finds my location. It seems overly complicated but easy enough. However following googles recommendations I am now trying to run this code as an Async task so it doesn't tie up the UI. However I can't even figure out how to get the code to compile never mind actually run. The error is that locationManager cannot be resolved when I reference it to remove the listeners. I have tried using the code posted on here Android find GPS location once, show loading dialog. However in this example currentLocation doesn't seemed to be referenced to anything and I ran into problems trying to sort that out. I have wasted nearly a full day trying to sort this problem so I would really appreciate if somebody can point me in the right direction.

private class LocationControl extends AsyncTask<Context, Void, Location> {
    public Location alocation;
    private LocatoinManager locationManager;

    @Override
    public Location doInBackground(Context... params) {
         locationManager = (LocationManager) params[0].getSystemService(Context.LOCATION_SERVICE);        
          locationManager.requestLocationUpdates(locationManager.GPS_PROVIDER, 0, 0, locationListener);
        return alocation;
    }

    public LocationListener locationListener = new LocationListener() {

            public void onStatusChanged(String provider, int status, Bundle extras) {}
            public void onProviderEnabled(String provider) {}
            public void onProviderDisabled(String provider) {}

            public void onLocationChanged(android.location.Location mlocation) {
                saveLocation(mlocation);
                locationManager.removeUpdates(locationListener);
            }
    };  

    void saveLocation(android.location.Location location){
        alocation = location;   
    }

    @Override
    protected void onPostExecute(Location result) {
        useLocation(result);
        super.onPostExecute(result);
    }

    @Override
    protected void onPreExecute() {
        dialog.show(WasserSportLotse.this, " ", "Finding location...");

        super.onPreExecute();
    }
}

So I changed the code with your recommendations and it now compiles. I have update the code on here to represent what I am running. I am getting a runtime error when the locationManager requestsLocationUpdates. Here is the logCat. Any Ideas?

04-15 14:57:56.742: ERROR/AndroidRuntime(18328): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception
04-15 14:57:56.942: ERROR/AndroidRuntime(18328): java.lang.RuntimeException: An error occured while executing doInBackground()
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.util.concurrent.FutureTask.run(FutureTask.java:122)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.lang.Thread.run(Thread.java:1060)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.os.Handler.<init>(Handler.java:121)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.location.LocationManager$ListenerTransport$1.<init>(LocationManager.java:128)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.location.LocationManager$ListenerTransport.<init>(LocationManager.java:126)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.location.LocationManager._requestLocationUpdates(LocationManager.java:697)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.location.LocationManager.requestLocationUpdates(LocationManager.java:619)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at com.WasserSportLotse.WasserSportLotse$LocationControl.doInBackground(WasserSportLotse.java:62)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at com.WasserSportLotse.WasserSportLotse$LocationControl.doInBackground(WasserSportLotse.java:1)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256)
04-15 14:57:56.942: ERROR/AndroidRuntime(18328):     ... 4 more
04-15 14:58:23.451: ERROR/AndroidRuntime(18356): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception
04-15 14:58:23.642: ERROR/AndroidRuntime(18356): java.lang.RuntimeException: An error occured while executing doInBackground()
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.util.concurrent.FutureTask.run(FutureTask.java:122)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.lang.Thread.run(Thread.java:1060)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.os.Handler.<init>(Handler.java:121)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.location.LocationManager$ListenerTransport$1.<init>(LocationManager.java:128)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.location.LocationManager$ListenerTransport.<init>(LocationManager.java:126)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.location.LocationManager._requestLocationUpdates(LocationManager.java:697)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.location.LocationManager.requestLocationUpdates(LocationManager.java:619)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at com.WasserSportLotse.WasserSportLotse$LocationControl.doInBackground(WasserSportLotse.java:62)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at com.WasserSportLotse.WasserSportLotse$LocationControl.doInBackground(WasserSportLotse.java:1)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256)
04-15 14:58:23.642: ERROR/AndroidRuntime(18356):     ... 4 more

score 27 · Accepted Answer · edited Nov 02 '12 at 12:46

public class FastMainActivity extends Activity {

    Button searchBtn = null;
    Intent locatorService = null;
    AlertDialog alertDialog = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        searchBtn = (Button) findViewById(R.id.searchBtn);

        searchBtn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                if (!startService()) {
                    CreateAlert("Error!", "Service Cannot be started");
                } else {
                    Toast.makeText(FastMainActivity.this, "Service Started",
                            Toast.LENGTH_LONG).show();
                }

            }
        });

    }

    public boolean stopService() {
        if (this.locatorService != null) {
            this.locatorService = null;
        }
        return true;
    }

    public boolean startService() {
        try {
            // this.locatorService= new
            // Intent(FastMainActivity.this,LocatorService.class);
            // startService(this.locatorService);

            FetchCordinates fetchCordinates = new FetchCordinates();
            fetchCordinates.execute();
            return true;
        } catch (Exception error) {
            return false;
        }

    }

    public AlertDialog CreateAlert(String title, String message) {
        AlertDialog alert = new AlertDialog.Builder(this).create();

        alert.setTitle(title);

        alert.setMessage(message);

        return alert;

    }

    public class FetchCordinates extends AsyncTask<String, Integer, String> {
        ProgressDialog progDailog = null;

        public double lati = 0.0;
        public double longi = 0.0;

        public LocationManager mLocationManager;
        public VeggsterLocationListener mVeggsterLocationListener;

        @Override
        protected void onPreExecute() {
            mVeggsterLocationListener = new VeggsterLocationListener();
            mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

            mLocationManager.requestLocationUpdates(
                    LocationManager.NETWORK_PROVIDER, 0, 0,
                    mVeggsterLocationListener);

            progDailog = new ProgressDialog(FastMainActivity.this);
            progDailog.setOnCancelListener(new OnCancelListener() {
                @Override
                public void onCancel(DialogInterface dialog) {
                    FetchCordinates.this.cancel(true);
                }
            });
            progDailog.setMessage("Loading...");
            progDailog.setIndeterminate(true);
            progDailog.setCancelable(true);
            progDailog.show();

        }

        @Override
        protected void onCancelled(){
            System.out.println("Cancelled by user!");
            progDialog.dismiss();
            mLocationManager.removeUpdates(mVeggsterLocationListener);
        }

        @Override
        protected void onPostExecute(String result) {
            progDailog.dismiss();

            Toast.makeText(FastMainActivity.this,
                    "LATITUDE :" + lati + " LONGITUDE :" + longi,
                    Toast.LENGTH_LONG).show();
        }

        @Override
        protected String doInBackground(String... params) {
            // TODO Auto-generated method stub

            while (this.lati == 0.0) {

            }
            return null;
        }

        public class VeggsterLocationListener implements LocationListener {

            @Override
            public void onLocationChanged(Location location) {

                int lat = (int) location.getLatitude(); // * 1E6);
                int log = (int) location.getLongitude(); // * 1E6);
                int acc = (int) (location.getAccuracy());

                String info = location.getProvider();
                try {

                    // LocatorService.myLatitude=location.getLatitude();

                    // LocatorService.myLongitude=location.getLongitude();

                    lati = location.getLatitude();
                    longi = location.getLongitude();

                } catch (Exception e) {
                    // progDailog.dismiss();
                    // Toast.makeText(getApplicationContext(),"Unable to get Location"
                    // , Toast.LENGTH_LONG).show();
                }

            }

            @Override
            public void onProviderDisabled(String provider) {
                Log.i("OnProviderDisabled", "OnProviderDisabled");
            }

            @Override
            public void onProviderEnabled(String provider) {
                Log.i("onProviderEnabled", "onProviderEnabled");
            }

            @Override
            public void onStatusChanged(String provider, int status,
                    Bundle extras) {
                Log.i("onStatusChanged", "onStatusChanged");

            }

        }

    }

}

+1. This is a great example that avoids Loopers, which can be confusing. — rmigneco, Mar 24 '14 at 00:44
This code doesn't run the location manager in background, but in the onPreExecute() method, which runs in the UI thread. — Alessandro Roaro, May 06 '14 at 17:02
@SpinalTapFan11 Agreed, it replaces it with just a simple loop, `while (this.lati == 0.0) {}`. — Joshua Pinter, Aug 16 '14 at 16:19
@SALMAN can u explain what is use of asyn task when doInBackground() method just loop(wait) doing nothing... and all the work load in on the Ui thread — FaisalAhmed, Dec 21 '17 at 05:47

score 4 · Answer 2 · answered Jun 19 '13 at 06:22

4

Just add Looper.prepare() before calling locationManager.requestLocationUpdates(locationManager.GPS_PROVIDER, 0, 0, locationListener); Remember to call Looper.loop() after.

answered Jun 19 '13 at 06:22

jibysthomas

1,601
2
16
24

what about if I want to stop this loop? – Anderson Aug 02 '16 at 03:02

score 1 · Answer 3 · answered Apr 15 '11 at 12:35

1

First to fix your compilation problem, move

LocationManager locationManager = (LocationManager)params[0].getSystemService(Context.LOCATION_SERVICE);

So that it's a private member variable of the class.

LocationManager does not have to be in an AsyncTask. It does not tie up the UI, all updates are already asynchronous. This will just add needless complication to your project.

You probably only need to move useLocation into onLockationChanged.

answered Apr 15 '11 at 12:35

Mike dg

4,648
2
27
26

I suggest getting rid of the AsyncTask. The runtime error might just go away. – Mike dg Apr 15 '11 at 13:07
Thats how I originally had the app working however I have a splash screen and I would like to show a dialog when I am getting the location. The dialog was freezing when doing this. hence the need for the asyntask. – jiduvah Apr 15 '11 at 13:13
@Mike Do you have a reference that explains how `LocationManager` works asynchronously? There's nothing about it that I could find on the reference page. – thegrinner Jul 05 '11 at 14:03

How To Get Location Using AsyncTask

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