Question

Working on some check-in functionality for an application, and trying to figure out the cleanest way to handle the lastKnowLocation being null. Currently, I attach a location listener and then fire off an asynctask which publishes an indeterminate progressdialog, alerting the user that I am searching for a the gps to gather their location; the doInBackground method is essentially just a busy wait loop, waiting on the location to not be null. As a disclaimer, I feel like this current implementation is bit “jenky” from a code standpoint, but provides the expected user experience. However, I am wondering if anybody could provide insight as to what would be a better way to handle this fairly common scenario.

Thanks

Answer 1

I’m not for the progress dialog because if the GPS takes forever then so will your app, killing the UX. In the activity with the dialog why not have a global locationFound boolean, a lastLongitude and lastLatitude. The advantage of that being if the you use the GPS returned to open another activity and the user navigates backwards you can even implement a “See previous results” or whatever the terminology is for your app. Here’s how i implemented a GPS location wait in an activity for a small app i did a while ago, excluding the code that doesn’t matter for your question

public class MainActivity extends Activity {
        TextView txt;
        Button btnGPS;
        Button btnSeeLast;
        LocationManager locationManager;
        String provider;
        boolean gotLoc;
        boolean hasLastLoc;
        double lastLat;
        double lastLon;
        LocationListener myLocationListener;


    @Override
public void onDestroy(){
    super.onDestroy();
    locationManager.removeUpdates(myLocationListener);  

}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        .....
        txt = (TextView)findViewById(R.id.tekst);
        txt.setText("Waiting for GPS location");
        btnSeeLast = (Button)findViewById(R.id.btnSeeLast);
        btnSeeLast.setEnabled(false);
        hasLastLoc = false;
        String context = Context.LOCATION_SERVICE;
        gotLoc = false;
        locationManager = (LocationManager)getSystemService(context);
        provider = LocationManager.GPS_PROVIDER;
        myLocationListener = new UpdatesReceiver();
        int t = 5000;
        int distance = 5;
        locationManager.requestLocationUpdates(provider, t, distance, myLocationListener);
        checkGPS();
        Location location = locationManager.getLastKnownLocation(provider);
        if (location != null){
        gotLoc = true;
        updateWithNewLocation(location, true);
        }
      }

private void checkGPS(){
    if (!locationManager.isProviderEnabled(provider)){
        buildAlertMessageNoGps();
        }   
}

public void btnSeeLastClick(View view){
    Intent intent = new Intent(this, NextActivity.class);
    intent.putExtra("latitude", String.valueOf(lastLat));
    intent.putExtra("longitude", String.valueOf(lastLon));
    intent.putExtra("prev", false);     
    startActivity(intent);

}


private void updateWithNewLocation(Location location, boolean prev){
    btnGPS.setEnabled(true);
    String latLongString;

    if (location != null){
        double lat = location.getLatitude();
        double lng = location.getLongitude();

        //remember
        lastLat = lat;
    lastLon = lng;
    hasLastLoc = true;
    btnSeeLast.setEnabled(true);
        //end remember
        latLongString = "Latitude: " + lat + "\nLongitude: " + lng;
        txt.setText("");
        //txt.setText(latLongString);return;

        Intent intent = new Intent(this, AgentsList.class);
        intent.putExtra("latitude", String.valueOf(lat));
        intent.putExtra("longitude", String.valueOf(lng));

        if (prev){
            intent.putExtra("prev", true);              
        }
        else{
            intent.putExtra("prev", false);
        }
        startActivity(intent);

        }
    else{
        latLongString = "Failed to get a response from your GPS. Try again";
        txt.setText(latLongString);
        }



}

private class UpdatesReceiver implements LocationListener{
    @Override
    public void onLocationChanged(Location location) {
        if (gotLoc == false){
            gotLoc = true;
            updateWithNewLocation(location, false);


        }           

    }

    @Override
    public void onProviderDisabled(String provider){
    // Update application if provider disabled.
    }

    @Override
    public void onProviderEnabled(String provider){
    // Update application if provider enabled.
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras){
    // Update application if provider hardware status changed.
    }
}
}