Map view following user - MyLocationOverlay type functionality for Android Maps API v2

Question

I switched to v2 of Maps for Android, and I am trying to port over the following functionality:

With MyLocationOverlay I can show the devices current location (Blue Dot). When the user's location changes and the dot reaches the edge of the visible area, the map animates out so the dot becomes the center of the view, in real time.

In v2, I am using SupportMapFragment with getMap().setMyLocationEnabled(true). The current location appears as a blue dot(arrow), but when the device changes location, the map view does not shift and the dot eventually leaves the view.

Any ideas?

Answer 1

You need to add a LocationSource to your GoogleMap and respond to onLocationChanged events. Here is a simple class that asks for the user's location, then waits until the user's location is available and animates the map to center on their location.

public class MyLocationMapFragmentActivity extends FragmentActivity implements LocationListener, LocationSource
{
/**
 * Note that this may be null if the Google Play services APK is not available.
 */
private GoogleMap mMap;

private OnLocationChangedListener mListener;
private LocationManager locationManager;

@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);

    setContentView(R.layout.basic_map);

    locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

    if(locationManager != null)
    {
        boolean gpsIsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
        boolean networkIsEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if(gpsIsEnabled)
        {
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000L, 10F, this);
        }
        else if(networkIsEnabled)
        {
            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 5000L, 10F, this);
        }
        else
        {
            //Show an error dialog that GPS is disabled.
        }
    }
    else
    {
        //Show a generic error dialog since LocationManager is null for some reason
    }

    setUpMapIfNeeded();
}

@Override
public void onPause()
{
    if(locationManager != null)
    {
        locationManager.removeUpdates(this);
    }

    super.onPause();
}

@Override
public void onResume()
{
    super.onResume();

    setUpMapIfNeeded();

    if(locationManager != null)
    {
        mMap.setMyLocationEnabled(true);
    }
}


/**
 * Sets up the map if it is possible to do so (i.e., the Google Play services APK is correctly
 * installed) and the map has not already been instantiated.. This will ensure that we only ever
 * call {@link #setUpMap()} once when {@link #mMap} is not null.
 * <p>
 * If it isn't installed {@link SupportMapFragment} (and
 * {@link com.google.android.gms.maps.MapView
 * MapView}) will show a prompt for the user to install/update the Google Play services APK on
 * their device.
 * <p>
 * A user can return to this Activity after following the prompt and correctly
 * installing/updating/enabling the Google Play services. Since the Activity may not have been
 * completely destroyed during this process (it is likely that it would only be stopped or
 * paused), {@link #onCreate(Bundle)} may not be called again so we should call this method in
 * {@link #onResume()} to guarantee that it will be called.
 */
private void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the map.
    if (mMap == null) 
    {
        // Try to obtain the map from the SupportMapFragment.
        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.basicMap)).getMap();
        // Check if we were successful in obtaining the map.

        if (mMap != null) 
        {
            setUpMap();
        }

        //This is how you register the LocationSource
        mMap.setLocationSource(this);
    }
}

/**
 * This is where we can add markers or lines, add listeners or move the camera. In this case, we
 * just add a marker near Africa.
 * <p>
 * This should only be called once and when we are sure that {@link #mMap} is not null.
 */
private void setUpMap() 
{
    mMap.setMyLocationEnabled(true);
}

@Override
public void activate(OnLocationChangedListener listener) 
{
    mListener = listener;
}

@Override
public void deactivate() 
{
    mListener = null;
}

@Override
public void onLocationChanged(Location location) 
{
    if( mListener != null )
    {
        mListener.onLocationChanged( location );

        //Move the camera to the user's location once it's available!
        mMap.animateCamera(CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));
    }
}

@Override
public void onProviderDisabled(String provider) 
{
    // TODO Auto-generated method stub
    Toast.makeText(this, "provider disabled", Toast.LENGTH_SHORT).show();
}

@Override
public void onProviderEnabled(String provider) 
{
    // TODO Auto-generated method stub
    Toast.makeText(this, "provider enabled", Toast.LENGTH_SHORT).show();
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) 
{
    // TODO Auto-generated method stub
    Toast.makeText(this, "status changed", Toast.LENGTH_SHORT).show();
}
}

This should follow the user and keep centering the map on their location as it changes - if you'd like to only center the map on the user when they go "off screen", then you could check to see if the user's location is within the visible bounds of the map

@Override
public void onLocationChanged(Location location) 
{
    if( mListener != null )
    {
        mListener.onLocationChanged( location );

        LatLngBounds bounds = this.mMap.getProjection().getVisibleRegion().latLngBounds;

        if(!bounds.contains(new LatLng(location.getLatitude(), location.getLongitude())))
        {
             //Move the camera to the user's location if they are off-screen!
             mMap.animateCamera(CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));
        }
    }
}

Here's a short write up on the topic: Google Maps Android API V2 MyLocation LocationSource and event handling

UPDATE

I edited how I'm obtaining the user's location (see locationManager code in onCreate). I've found that using the "getBestProvider" methods are not reliable and just plain don't work on several devices. I had several users complain that their devices would never find their location, no matter how relaxed I made the criteria. It seems that manually picking GPS or Network works universally.