如何在android中执行捏合放大或捏合缩小

Question

I'm working on an application in which I have used custom mapView, and on that mapView if user pinch(two finger gesture), the camera position for map should change accordingly, for eg. if user pinch zoom in, the camera zoom should zoom in for map (only center of the screen) and if user pinch zoom out, the camera zoom should be zoom out for the map(only center of the screen). I've tried for it but for zoom in and zoom out the map is always zooming in. Is there any way to find the distance between two finger that is increasing/decreasing, or gesture is pinch zoom out or pinch zoom in??

UPDATE

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private static final String TAG = MainActivity.class.getSimpleName();
    private static final int LOCATION_PERMISSION_CONSTANT = 34;

    private static final int REQUEST_CHECK_SETTINGS = 12;

    //private EnhanchedMapView mapView;
    private MapView mapView;

    private GoogleMap googleMap;
    private FusedLocationProviderClient mFusedLocationClient;
    private Location mLastLocation;
    LocationManager locationManager;
    private TextView tvCoordinates;
    private GoogleApiClient googleApiClient;



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

        bindUI();
        mapView.onCreate(savedInstanceState);
        fusedLocationMethod(savedInstanceState);
        getLocationPermission();
        //getLastLocation();
    }

    private void bindUI() {
        mapView = findViewById(R.id.map_view);
        tvCoordinates = findViewById(R.id.tv_coordinates);

    }

   public void fusedLocationMethod(Bundle savedInstanceState) {
        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
    }

    private void getLocationPermission() {
        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) {
            ActivityCompat.requestPermissions(this,
                    new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION, android.Manifest.permission.ACCESS_COARSE_LOCATION},
                    LOCATION_PERMISSION_CONSTANT);
            return;
        }
        getLastLocation();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case LOCATION_PERMISSION_CONSTANT:
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    if (googleApiClient == null) {
                        getLocationPermission();
                    } else {
                        getLocationPermission();
                    }
                } else {

                    Toast.makeText(this, "Permission Denied", Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }


    public void getLastLocation() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            return;
        }
        mFusedLocationClient.getLastLocation()
                .addOnSuccessListener(this, new OnSuccessListener<Location>() {
                    @Override
                    public void onSuccess(Location location) {
                        if (location == null) {
                            Log.w(TAG, "onSuccess:null");
                            return;
                        }

                        mLastLocation = location;
                        preLat = location.getLatitude();
                        preLong = location.getLongitude();
                        settingMap(location.getLatitude(), location.getLongitude());

                        try {
                            locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
                        } catch (Exception e) {
                            e.printStackTrace();
                            Log.d("Error", e.getMessage() + " 203");
                        }

                        if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

                            return;
                        }

                    }
                })
                .addOnFailureListener(this, new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.w(TAG, "getLastLocation:onFailure", e);
                    }
                });
    }

    private double preLat = 0.0;
    private double preLong = 0.0;

    //setting map
    private void settingMap(final double lat, final double longi) {
        mapView.getMapAsync(new OnMapReadyCallback() {


            @Override
            public void onMapReady(GoogleMap gglmap) {


                googleMap = gglmap;
                googleMap.getUiSettings().setAllGesturesEnabled(false);
                googleMap.clear();
                CameraPosition cameraPosition = new CameraPosition.Builder().target(new LatLng(lat, longi)).zoom(16).build();

                googleMap.moveCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));

                googleMap.getUiSettings().setMyLocationButtonEnabled(false);

                //permission for location
                if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

                    return;
                }
                googleMap.setMyLocationEnabled(true);


                //googleMap.getUiSettings().setAllGesturesEnabled(false);
                googleMap.setOnCameraIdleListener(new GoogleMap.OnCameraIdleListener() {
                    @Override
                    public void onCameraIdle() {

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

                        Projection projection = googleMap.getProjection();

                        LatLng geographicalPosition = projection.fromScreenLocation(new Point(mapViewWidth / 2, mapViewHeight / 2));
                        //     Toast.makeText(getActivity(),""+geographicalPosition.latitude+" , "+geographicalPosition.longitude,Toast.LENGTH_LONG).show();


                        tvCoordinates.setText(geographicalPosition.latitude + "   ,   " + geographicalPosition.longitude);
                    }
                });

            }
        });


    }


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


    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
        super.onSaveInstanceState(savedInstanceState);
        mapView.onSaveInstanceState(savedInstanceState);
    }

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

    @Override
    public void onStop() {
        super.onStop();
        mapView.onStop();
    }

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

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

    @Override
    public void onStart() {
        super.onStart();
        mapView.onStart();
    }


}

EnhancedMapView.java

public class EnhanchedMapView extends MapView implements OnMapReadyCallback {
    private long mLastTouchTime = -1;
    private static final int INVALID_POINTER_ID = -1;

    private OnMapReadyCallback mMapReadyCallback;
    private GoogleMap mGoogleMap;

    private float mPosX;
    private float mPosY;

    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;

    private void init() {
    }

    @Override
    public void getMapAsync(OnMapReadyCallback callback) {
        mMapReadyCallback = callback;

        super.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mGoogleMap = googleMap;
    }

    LatLng geographicalPosition;
    boolean isPinch = false;

    @Override
    public boolean dispatchTouchEvent(MotionEvent 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));

                        MarkerOptions markerOptions = new MarkerOptions();
                        markerOptions.position(geographicalPosition);
                        mGoogleMap.addMarker(markerOptions);
                        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);
                Log.d("Nirmal", "ACTION_POINTER_DOWN");
                isPinch = true;

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

                Projection projection = mGoogleMap.getProjection();

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


                break;

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

                isPinch = false;
                break;

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

            case MotionEvent.ACTION_MOVE:
                if (isPinch) {
                    if (mGoogleMap == null || geographicalPosition == null)
                        break;
                    //Log.d("Nirmal", "ACTION_MOVE");
                    Log.d("Nirmal", "" + event.getX() + " , " + event.getY());


                    float currentZoom = mGoogleMap.getCameraPosition().zoom;

                    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(geographicalPosition.latitude, geographicalPosition.longitude), currentZoom + 0.05f));

                }
                break;

        }

        return super.dispatchTouchEvent(event);
    }


}

Answer 1

As pskink recommended, you need ScaleGestureDetector object, which determines zoom "direction". Something like that:

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();
                return true;
            }

            @Override
            public void onScaleEnd(ScaleGestureDetector detector) {
                float currentZoom = mGoogleMap.getCameraPosition().zoom;
                if (scaleFactor > 1) {
                    // zoom in detected
                    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(mZoomCenter, currentZoom + 1));
                } else if (scaleFactor < 1) {
                    // zoom out detected
                    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(mZoomCenter, currentZoom - 1));
                }
                super.onScaleEnd(detector);
            }
        });

And you can use it in your EnhanchedMapView.dispatchTouchEvent() easily:

...
@Override
public boolean dispatchTouchEvent(MotionEvent event) {

    // just call .onTouchEvent() on your ScaleGestureDetector object
    mScaleDetector.onTouchEvent(event);

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

NB! You need to disable GoogleMap zoom gesture

@Override
public void onMapReady(GoogleMap googleMap) {
    mGoogleMap = googleMap;
    mGoogleMap.getUiSettings().setZoomGesturesEnabled(false);
    ...
}

and never enable it.