在 onInfoWindowClick 中获取当前位置

Question

我想使用 onInfoWindowClick 中用户的当前位置。我在 onLocationChangend 中找到了位置，但是当我单击信息 window 时应用程序崩溃了，我不确定在 onInfoWindowClick.[=15 中是否以正确的方式重新定位到当前位置=]

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

private void setUpMap() {
/*....*/
googleMap.setInfoWindowAdapter(new UserInfoWindowAdapter(getLayoutInflater()));
    googleMap.setOnInfoWindowClickListener(new GoogleMap.OnInfoWindowClickListener() {
        @Override
        public void onInfoWindowClick(Marker marker) {

            LatLng markerPosition = marker.getPosition();
            Location myLocation;

            myLocation.setLatitude(myposition.latitude);
            myLocation.setLongitude(myposition.longitude);

            Location markerLoc = new Location("marker");
            markerLoc.setLatitude(markerPosition.latitude);
            markerLoc.setLongitude(markerPosition.longitude);

            float meters = myLocation.distanceTo(markerLoc);

            if (meters < 200) {
                /*...*/
            } else {
                /*...*/
            }
        }
    });
}

 @Override
public void onLocationChanged(Location location) {
    LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
    myposition = new LatLng(location.getLatitude(), location.getLongitude());

    CameraPosition cameraPosition = new CameraPosition.Builder().target(myposition).zoom(14).build();
    googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
}

我得到的错误是：

Attempt to invoke virtual method 'void android.location.Location.setLatitude(double)' on a null object reference

Answer 1

第一个问题是您有一个空 Location 对象，因为您从未对其进行初始化。但是，由于 onLocationChanged() 为您提供了位置参考，因此无需转换为 LatLng 然后再转换回位置。所以，只需使用一个成员变量，即 Location:

public class MainActivity extends AppCompatActivity 
        implements OnMapReadyCallback,
        GoogleApiClient.ConnectionCallbacks, 
        GoogleApiClient.OnConnectionFailedListener, LocationListener {

        Location mLocation;
        //...............

然后只需在 onLocationChanged() 中设置您的 Location 成员变量。此外，如果您想要获得多个位置更新以跟踪用户的移动，请删除取消注册位置更新的调用。

@Override
public void onLocationChanged(Location location) {
    //LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
    //myposition = new LatLng(location.getLatitude(), location.getLongitude());

    //add this:
    mLocation = location;

    CameraPosition cameraPosition = new CameraPosition.Builder().target(myposition).zoom(14).build();
    googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
}

那么InfoWindowClickListener就简化了，使用前确保mLocation不为null即可：

googleMap.setInfoWindowAdapter(new UserInfoWindowAdapter(getLayoutInflater()));
    googleMap.setOnInfoWindowClickListener(new GoogleMap.OnInfoWindowClickListener() {
        @Override
        public void onInfoWindowClick(Marker marker) {

            //null check, do nothing if current location is not known:
            if (mLocation == null) return;

            LatLng markerPosition = marker.getPosition();

            Location markerLoc = new Location("marker");
            markerLoc.setLatitude(markerPosition.latitude);
            markerLoc.setLongitude(markerPosition.longitude);

            float meters = mLocation.distanceTo(markerLoc);

            if (meters < 200) {
                /*...*/
            } else {
                /*...*/
            }
        }
    });
}

在 onInfoWindowClick 中获取当前位置

Get current Location in onInfoWindowClick

android

location

google-maps

google-maps-android-api-2