Keep map centered regardless of where you pinch zoom on android

Solution 1:

I've founded complete solution after spending about 3 days to search on google. My answer is edited from https://stackoverflow.com/a/32734436/3693334.

public class CustomMapView extends MapView {

    private int fingers = 0;
    private GoogleMap googleMap;
    private long lastZoomTime = 0;
    private float lastSpan = -1;
    private Handler handler = new Handler();

    private ScaleGestureDetector scaleGestureDetector;
    private GestureDetector gestureDetector;

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

    public CustomMapView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public CustomMapView(Context context, AttributeSet attrs, int style) {
        super(context, attrs, style);
    }

    public CustomMapView(Context context, GoogleMapOptions options) {
        super(context, options);
    }

    public void init(GoogleMap map) {
        scaleGestureDetector = new ScaleGestureDetector(getContext(), new ScaleGestureDetector.OnScaleGestureListener() {
            @Override
            public boolean onScale(ScaleGestureDetector detector) {
                if (lastSpan == -1) {
                    lastSpan = detector.getCurrentSpan();
                } else if (detector.getEventTime() - lastZoomTime >= 50) {
                    lastZoomTime = detector.getEventTime();
                    googleMap.animateCamera(CameraUpdateFactory.zoomBy(getZoomValue(detector.getCurrentSpan(), lastSpan)), 50, null);
                    lastSpan = detector.getCurrentSpan();
                }
                return false;
            }

            @Override
            public boolean onScaleBegin(ScaleGestureDetector detector) {
                lastSpan = -1;
                return true;
            }

            @Override
            public void onScaleEnd(ScaleGestureDetector detector) {
                lastSpan = -1;

            }
        });
        gestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onDoubleTapEvent(MotionEvent e) {

                disableScrolling();
                googleMap.animateCamera(CameraUpdateFactory.zoomIn(), 400, null);

                return true;
            }
        });
        googleMap = map;
    }

    private float getZoomValue(float currentSpan, float lastSpan) {
        double value = (Math.log(currentSpan / lastSpan) / Math.log(1.55d));
        return (float) value;
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        gestureDetector.onTouchEvent(ev);
        switch (ev.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_POINTER_DOWN:
                fingers = fingers + 1;
                break;
            case MotionEvent.ACTION_POINTER_UP:
                fingers = fingers - 1;
                break;
            case MotionEvent.ACTION_UP:
                fingers = 0;
                break;
            case MotionEvent.ACTION_DOWN:
                fingers = 1;
                break;
        }
        if (fingers > 1) {
            disableScrolling();
        } else if (fingers < 1) {
            enableScrolling();
        }
        if (fingers > 1) {
            return scaleGestureDetector.onTouchEvent(ev);
        } else {
            return super.dispatchTouchEvent(ev);
        }
    }

    private void enableScrolling() {
        if (googleMap != null && !googleMap.getUiSettings().isScrollGesturesEnabled()) {
            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    googleMap.getUiSettings().setAllGesturesEnabled(true);
                }
            }, 50);
        }
    }

    private void disableScrolling() {
        handler.removeCallbacksAndMessages(null);
        if (googleMap != null && googleMap.getUiSettings().isScrollGesturesEnabled()) {
            googleMap.getUiSettings().setAllGesturesEnabled(false);
        }
    }
}

and customize MapFragment

public class CustomMapFragment extends Fragment {

        CustomMapView view;
        Bundle bundle;
        GoogleMap map;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            bundle = savedInstanceState;
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.fragment_map, container, false);

            view = (CustomMapView) v.findViewById(R.id.mapView);
            view.onCreate(bundle);
            view.onResume();

            map = view.getMap();
            view.init(map);

            MapsInitializer.initialize(getActivity());

            return v;
        }

        public GoogleMap getMap() {
            return map;
        }

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

        @Override
        public void onPause() {
            super.onPause();
            view.onPause();
        }

        @Override
        public void onDestroy() {
            super.onDestroy();
            view.onDestroy();
        }

        @Override
        public void onLowMemory() {
            super.onLowMemory();
            view.onLowMemory();
        }
    }

Finally, in your activity:

....
<fragment
    android:id="@+id/map"
    class="yourpackage.CustomMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>
...

I've already tested on Android 4.1 (API 16) and latter, it work fine and smooth. (About API < 16, I haven't any device to test).

Solution 2:

Here's the code for what MechEthan is thinking of.

First you have to detect double-tap on an overlay view.

public class TouchableWrapper extends FrameLayout {
    private final GestureDetector.SimpleOnGestureListener mGestureListener
            = new GestureDetector.SimpleOnGestureListener() {
        @Override
        public boolean onDoubleTap(MotionEvent e) {

            //Notify the event bus (I am using Otto eventbus of course) that you have just received a double-tap event on the map, inside the event bus event listener
            EventBus_Singleton.getInstance().post(new EventBus_Poster("double_tapped_map"));

            return true;
        }
    };

    public TouchableWrapper(Context context) {
        super(context);
        mGestureDetector = new GestureDetectorCompat(context, mGestureListener);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        mGestureDetector.onTouchEvent(ev);

        return super.onInterceptTouchEvent(ev);
    }
}

Wherever it is that you are grabbing your mapView, wrap that mapView inside the TouchableWrapper created above. This is how I do it because I have the issue of needing to add a mapFragment into another fragment so I need a custom SupportMapFragment to do this

public class CustomMap_Fragment extends SupportMapFragment {

    TouchableWrapper mTouchView;

    public CustomMap_Fragment() {
        super();
    }

    public static CustomMap_Fragment newInstance() {
        return new CustomMap_Fragment();
    }

    @Override
    public View onCreateView(LayoutInflater arg0, ViewGroup arg1, Bundle arg2) {
        View mapView = super.onCreateView(arg0, arg1, arg2);

        Fragment fragment = getParentFragment();
        if (fragment != null && fragment instanceof OnMapReadyListener) {
            ((OnMapReadyListener) fragment).onMapReady();
        }

        mTouchView = new TouchableWrapper(getActivity());
        mTouchView.addView(mapView);

        return mTouchView;
    }

    public static interface OnMapReadyListener {
        void onMapReady();
    }
}

Inside my Map_Fragment (which in the end will sit inside a FrameLayout in an activity that supports navigation drawer and fragment transactions for switching the views)
```
mMapFragment = CustomMap_Fragment.newInstance();
getChildFragmentManager().beginTransaction().replace(R.id.map_container, mMapFragment).commit();
```

Now finally inside this same Fragment where I just got my map, the EventBus receiver will do the following action when it receives "double_tapped_map":

@Subscribe public void eventBus_ListenerMethod(AnswerAvailableEvent event) {
    //Construct a CameraUpdate object that will zoom into the exact middle of the map, with a zoom of currentCameraZoom + 1 unit
   zoomInUpdate = CameraUpdateFactory.zoomIn();
   //Run that with a speed of 400 ms.
   map.animateCamera(zoomInUpdate, 400, null);
}

Note: To achieve this perfectly you disable zoomGestures on your map (meaning you do myMap.getUiSettings().setZoomGesturesEnabled(false);. If you don't do that, you will be able to double-tap very quickly on the map and you will see that it will zoom away from the center because the implementation of double tap is exactly as I had in the first answer I posted, which is that they subtract current time from previous tap-time, so in that window you can slip in a third tap and it will not trigger the event bus event and google map will catch it instead; So disable Zoom gestures.

But then, you will see that pinch-in/out will not work anymore and you have to handle pinch also, which I've also done but needs like 1 more hour and I havent gotten the time to do that yet but 100% I will update the answer when I do that.

TIP: Uber has disabled rotate gestures on the map also. map.getUiSettings().setRotateGesturesEnabled(false);

Solution 3:

Personally, I would disable only zoom gestures on the map, detect pinch on an overlay, and then pass everything else through to the map.

The google-maps v2 API doesn't have anything explicit for custom zoom handling. Although I'm sure you could inject something, doing the overlay approach insulates you from google-maps changes, and lets you more easily support other map providers if needed.

(Just for completeness: you could also handle the post-camera change events and re-center, but that would be a janky, bad user experience.)

Keep map centered regardless of where you pinch zoom on android

Solution 1:

Solution 2:

Solution 3:

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