How do I measure Google Maps' camera viewport in meters?

Question

Specification:

I want to zoom the camera based on the markers' distances. If all the markers present in the Google Maps cannot be entirely covered on a street level zoom(15) , then switch to another built-in zoom function: CameraUpdateFactory.newLatLngBounds(bounds, width, height, padding), which satisfies the requirement. I refrain from using this built-in function when the markers are too close to each other or there's only one marker because it zooms on the maximum level. I have tried to use GoogleMap#setMaxZoomPreference but it doesn't seem to work. The zoom level does not necessarily prohibits to clamp on a certain maximum value(which setting a max zoom level becomes void) but I need to set the initial zoom where the user can see all of the markers present in the entire map.

Question:

How do I measure the camera viewport in meters?

Thoughts:

I will be needing the viewable area and gather all the distances of markers to determine if I will use the street level zoom level or the built-in zoom function.

Answer 1

You can measure the viewport width and height on each camera change like this:

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, GoogleMap.OnCameraIdleListener {
    private GoogleMap mMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(final GoogleMap googleMap) {
        mMap = googleMap;
        mMap.setOnCameraIdleListener(this);
    }

    @Override
    public void onCameraIdle() {
        VisibleRegion viewPort = mMap.getProjection().getVisibleRegion();
        double viewPortHeight = SphericalUtil.computeDistanceBetween(viewPort.nearLeft, viewPort.farLeft);
        double viewPortWidth = SphericalUtil.computeDistanceBetween(viewPort.nearLeft, viewPort.nearRight);
    }
}

I'm using the SphericalUtil.computeDistanceBetween method from the Google Maps Android API Utility Library