Animating car Marker movement on map V2

问题

I am animating car moving on a street with real time location updates. But the car is facing to true north and the bearing returns 0.0 no matter which direction I am moving. Is there any hack to make the front of my car moving the direction I am moving. Here is my code.

private void draw_current_location(Location currentlocation) {
        LatLng current = new LatLng(currentlocation.getLatitude(), currentlocation.getLongitude());
        CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(current, 15);
        map.animateCamera(cameraUpdate);
        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            return;
        }
        Location calculatedLoc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if(locationManager.getProvider(LocationManager.GPS_PROVIDER).supportsBearing()) {
            float bearing = calculatedLoc.bearingTo(currentlocation);
            centeredMap(current, bearing);
        }
    }

    void centeredMap(final LatLng lalng, float bearng){
        Location l = new Location("");
        l.setLatitude(lalng.latitude);
        l.setLongitude(lalng.longitude);
        View marker = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.custom_marker_layout, null);
        if (customMarker != null) customMarker.remove();
        customMarker = map.addMarker(new MarkerOptions()
                .position(lalng)
                .title("Title")
                .snippet("Description")
                .anchor(0.5f, 0.5f)
                .flat(true)
                .rotation(bearng)
                .icon(BitmapDescriptorFactory.fromResource(R.drawable.customIMAGE)));
        Toast.makeText(getApplicationContext(), String.valueOf(l.getBearing()), Toast.LENGTH_SHORT).show();
        customMarker.setPosition(lalng);
        animation.animateMarker(l, customMarker);
}

UPDATE: Now the bearing is returning values. After I edited my code as such.

if(locationManager.getProvider(LocationManager.GPS_PROVIDER).supportsBearing()) {
            Location calculatedLoc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
            float bearing = calculatedLoc.bearingTo(currentlocation);
            Toast.makeText(getApplicationContext(), String.valueOf(bearing), Toast.LENGTH_SHORT).show();
            centeredMap(currentlocation, bearing);
        }

But the marker is rotating along the center vertical axis because of the anchor(.5f, .5f) but it doesn't RECOGNIZE my car marker's front so it doesn't animate along the street. The car is simply static image facing north and being dragged when I move. Any help would be much appreciated.

回答1:

I got it to work. I was gonna pull my hairs on this one. I was even gonna draw multiple cars with different rotation and animate between all using a switch case or something. But I didn't go that far. I had a static car facing north with anchor at (.5,.5) and drove to a distance to actually matter then it starts to rotate and follow my direction. 1) The bearing is only accurate if there is few seconds difference between the first location and the second. (The closer the location updates the less accurate the bearing)To do that it is better to grab locations further apart and animate direction based on the bearing you get; which is not real time animation(with some latency but great animation that looks like real). 2)You have to use GPS provider to get bearing.

来源：https://stackoverflow.com/questions/35449269/animating-car-marker-movement-on-map-v2