Google Map Heading Marker or Indicator

Question

The "Google Maps" app in Jellybean has an indicator which adjusts based on the way you're facing. I am interested in implementing a similar indicator but for multiple indicators.

Does anyone have an idea on how they implemented their heading indicator (note it maintains its heading even when the map is rotated). I attempted my own approach using markers, then I realized that markers will not rotate with the map (kind of an oh duh moment after a few hours of labor...)

To summarize: How do I implement an icon in google maps that rotates based on heading, and not the map.

So as of right now I see two solutions:

• Capture map rotation and transfer it to the marker
• Draw over the map using OpenGL

Could anyone offer any advice before I start down another rabbit hole? Thanks!

Answer 1

There are a couple things you can do if you want to show orientation on a map.

Here are all of the imports that are used:

import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;

1.Move the map so that the bearing is on top.

private final GoogleMap mMap;

//Get the current position from the map
CameraPosition camPosition = mMap.getCameraPosition();

//Update only the orientation/bearing, get all of the other values from the existing position.
CameraPosition newPos = new CameraPosition(
   camPosition.target,
   camPosition.zoom,        
   camPosition.tilt,
   azimuthInDegress);

//Set the position so that the map will update. The desired heading should not be on top
mMap.moveCamera(CameraUpdateFactory.newCameraPosition(newPos));

The problem with this idea is that if you don't stabilize your orientation updates, the map will move all over the place.

2.Implement a LocationSource

Google maps give you the ability to override it's location provider. First you'll want to implement a new Location source:

import android.app.Activity;
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.LocationSource;
import com.google.android.gms.maps.MapFragment;


public class LocationSourceImplActivity extends Activity {


@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    //Assume using the example from Google
    GoogleMap map = ((MapFragment) getFragmentManager()
            .findFragmentById(R.id.map)).getMap();

    map.setMyLocationEnabled(true);

    LocationManager locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

    map.setLocationSource(new LocationSourceImpl(locManager));
}

    /**
    *The Goal of this class is to listen for both location and heading updates 
    *and combine these into a single update, which will be passed to Google Maps.
    */ 
private class LocationSourceImpl implements LocationSource, LocationListener {

    private OnLocationChangedListener mListener = null;
    private Location mLastLoc = null;
    //Use your desired location provider. You can also update this class to better
    //determine when and how to register
    private static final String PREF_LOC_SRC ="";
    private final LocationManager mLocationManager;
    private float mLastHeading = Float.MAX_VALUE;


    public LocationSourceImpl(LocationManager pLocManager) {
        mLocationManager = pLocManager;

        //Get all updates, modify as desired. 
        mLocationManager.requestLocationUpdates(PREF_LOC_SRC, 0, 0, this);
    }

    @Override
    public void onLocationChanged(Location location) {
        mLastLoc = location;
        notifyListener();
    }

    private void notifyListener() {

        if(mListener != null && mLastLoc!=null) {

            if(mLastHeading != Float.MAX_VALUE) {
                mLastLoc.setBearing(mLastHeading);
            }

            //The listener will be the maps: 
            mListener.onLocationChanged(mLastLoc);

        }

    }

    @Override
    public void activate(OnLocationChangedListener pListener) {
                    //When the setLocationSource is called on the map, the map
                    //will be passed in as an OnLocationChangedListener (may not be the
                    //map, but may be a delegator created by the map. 
        mListener = pListener;
    }

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

    }

    /**
     * This method can/should be replaced with a heading calculation
     * @param pDegrees
     *  Heading in degrees
     */
    public void updateHeadingInDegrees(float pDegrees) {
        mLastHeading = pDegrees;
        notifyListener();

    }

    @Override
    public void onProviderDisabled(String paramString) {

    }

    @Override
    public void onProviderEnabled(String paramString) {

    }

    @Override
    public void onStatusChanged(String paramString, int paramInt,
            Bundle paramBundle) {

    }

}

}