In google map using pinch to zoom in and zoom out with the current location as centre of the map

Question

In my current android application, User will have the option to select their address by placing the marker on the map. The marker always stays in the center of the map. When the user is trying to zoom into the location by using gestures (pinching the map), the marker is changing its position, while using the zoom buttons everything is fine. How do I avoid moving the marker in the gesture case by moving the marker when using a single finger and only applying the gestures when using multiple fingers.

Answer 1

Create TouchableWrapper and use it in MapFragment

public class TouchableWrapper extends FrameLayout {

    private GoogleMap mGoogleMap = null;

    public TouchableWrapper(Context context) {
        super(context);
    }

    public void setGoogleMap(GoogleMap googleMap) {
        mGoogleMap = googleMap;
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        mScaleDetector.onTouchEvent(event);

        switch (event.getAction() & MotionEvent.ACTION_MASK) {

            case MotionEvent.ACTION_DOWN:
                mGoogleMap.getUiSettings().setScrollGesturesEnabled(true);

            long thisTime = System.currentTimeMillis();
            if (thisTime - mLastTouchTime < ViewConfiguration.getDoubleTapTimeout()) {

                if (mGoogleMap != null) {
                    LatLng zoomCenter = mGoogleMap.getProjection().fromScreenLocation(new Point((int) event.getX(), (int) event.getY()));
                    float currentZoom = mGoogleMap.getCameraPosition().zoom;

                    int mapViewHeight = getHeight();
                    int mapViewWidth = getWidth();

                    Projection projection = mGoogleMap.getProjection();

                    geographicalPosition = projection.fromScreenLocation(new Point(mapViewWidth / 2, mapViewHeight / 2));

                    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(geographicalPosition.latitude, geographicalPosition.longitude), currentZoom + 1));

                }
                mLastTouchTime = -1;
            } else {
                mLastTouchTime = thisTime;
                mGoogleMap.getUiSettings().setZoomGesturesEnabled(false);
            }
            break;

            case MotionEvent.ACTION_POINTER_DOWN:
                 mGoogleMap.getUiSettings().setZoomGesturesEnabled(false);
            mGoogleMap.getUiSettings().setScrollGesturesEnabled(false);
            break;

            case MotionEvent.ACTION_POINTER_UP:
                mGoogleMap.getUiSettings().setScrollGesturesEnabled(true);
            break;

            case MotionEvent.ACTION_UP:
               mGoogleMap.getUiSettings().setScrollGesturesEnabled(true);
            break;
        }

        return super.dispatchTouchEvent(event);
    }



ScaleGestureDetector mScaleDetector = new ScaleGestureDetector(getContext(),
        new ScaleGestureDetector.SimpleOnScaleGestureListener() {

            private float scaleFactor = 1f;

            @Override
            public boolean onScale(ScaleGestureDetector detector) {
                // store scale factor for detect zoom "direction" on end
                scaleFactor = detector.getScaleFactor();
                float currentZoom = mGoogleMap.getCameraPosition().zoom;
                int mapViewHeight = getHeight();
                int mapViewWidth = getWidth();
                if (scaleFactor > 1) {
                    // zoom in detected
                    geographicalPosition = mGoogleMap.getProjection().fromScreenLocation(new Point(mapViewWidth / 2, mapViewHeight / 2));
                    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(geographicalPosition, currentZoom + 0.05f));

                } else if (scaleFactor < 1) {
                    // zoom out detected
                    geographicalPosition = mGoogleMap.getProjection().fromScreenLocation(new Point(mapViewWidth / 2, mapViewHeight / 2));
                    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(geographicalPosition, currentZoom - 0.05f));
                }
                return true;
            }

            @Override
            public void onScaleEnd(ScaleGestureDetector detector) {

                super.onScaleEnd(detector);
            }
        });

}

MapFragment for that should be customized like:

public class MultiTouchMapFragment extends MapFragment {
    public View mOriginalContentView;
    public TouchableWrapper mTouchView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
        mOriginalContentView = super.onCreateView(inflater, parent, savedInstanceState);
        mTouchView = new TouchableWrapper(getActivity());
        mTouchView.addView(mOriginalContentView);
        return mTouchView;
    }

    @Override
    public View getView() {
        return mOriginalContentView;
    }
}

in MainActivity:

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback {

    private GoogleMap mGoogleMap;
    private MultiTouchMapFragment mMapFragment;

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

        mMapFragment = (MultiTouchMapFragment) getFragmentManager()
                .findFragmentById(R.id.map_fragment);
        mMapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mGoogleMap = googleMap;
        mMapFragment.mTouchView.setGoogleMap(mGoogleMap);
    }

}