How to get center of map for v2 android maps?

问题

In Google Maps for Android v1, MapView had a convenience method: getMapCenter(). Now I cannot figure out how to get map center with v2 of this api. I have perused the API documentation, but there is no mention of such a feature. Please advise.

Thanks, Igor

回答1:

I had the same problem. It seems you can get the center this way:

mMap.getCameraPosition().target

where mMap is the GoogleMap instance from your activity. This will return a LatLng object which basically represents the center of the map.

Note that the GeoPoint class is not available anymore.

According to http://developer.android.com/reference/com/google/android/gms/maps/model/CameraPosition.html

target is "The location that the camera is pointing at." (I tested it with the sample code and it worked okay for me)

回答2:

I have found two ways of do this:

1) The easiest, The first is using the target property in the Map's CameraPosition Object

 LatLng center = mMap.getCameraPosition().target;

2) The second is using a VisibleRegion object:

VisibleRegion visibleRegion = mMap.getProjection()
                    .getVisibleRegion();

Point x = mMap.getProjection().toScreenLocation(
                    visibleRegion.farRight);

Point y = mMap.getProjection().toScreenLocation(
                    visibleRegion.nearLeft);

Point centerPoint = new Point(x.x / 2, y.y / 2);

LatLng centerFromPoint = mMap.getProjection().fromScreenLocation(
                    centerPoint);

I have compared both answers:

Log.d("MapFragment: ", "Center From camera: Long: " + center.longitude
                        + " Lat" + center.latitude);

Log.d("Punto x", "x:" + x.x + "y:" + x.y);
Log.d("Punto y", "y:" + y.x + "y:" + y.y);

Log.d("MapFragment: ", "Center From Point: Long: "
                    + centerFromPoint.longitude + " Lat"
                    + centerFromPoint.latitude);

回答3:

You can use :

latlng=map.getProjection().getVisibleRegion().latLngBounds.getCenter();

回答4:

to get center of map I used onMapReady() method in activity, then used googleMap.setOnCameraChangeListener() method to get position of Came:

@Override
public void onMapReady(GoogleMap googMap) {
    googleMap.setOnCameraChangeListener(new GoogleMap.OnCameraChangeListener() {
        @Override
        public void onCameraChange(CameraPosition cameraPosition) {

       Log.i("centerLat",cameraPosition.target.latitude);

       Log.i("centerLong",cameraPosition.target.longitude);

        }
    });
}

回答5:

If you only want to get the position once (e.g. after the user has stopped panning the map), use setOnCameraIdleListener:

https://developers.google.com/android/reference/com/google/android/gms/maps/GoogleMap.OnCameraIdleListener

mMap.setOnCameraIdleListener(new GoogleMap.OnCameraIdleListener() {
    @Override
    public void onCameraIdle() {
        LatLng position = mMap.getCameraPosition().target;
        Log.d("MapActivity", "Position: " + position);
    }
});

or using a Java 8 lambda:

mMap.setOnCameraIdleListener(() -> {
    LatLng position = mMap.getCameraPosition().target;
    Log.d("MapActivity", "Position: " + position);
});

Note that the listener registered with setOnCameraChangeListener is called many times, and as the documentation states:

This may be called as often as once every frame and should not perform expensive operations.

回答6:

best way use cameraPosition

java:

LatLng centerMap = googleMap.getCameraPosition().target;

kotlin:

googleMap?.cameraPosition?.target?.let {
    // it is LatLng center
}

来源：https://stackoverflow.com/questions/13904505/how-to-get-center-of-map-for-v2-android-maps

标签

android

google-maps-api-2