java - 谷歌地图 GPS : longitude and latitude returns zero

Question

我需要从 Main 类获取位置或纬度经度，但如果我获取位置它返回 null，如果我获取纬度和经度则返回 0.0，如下面的代码所示。尽量减少代码并使其尽可能清晰。

这是我需要从主类获取位置的服务类

public void onLocationChanged(Location location)
    {
        Log.e(TAG, "onLocationChanged: " + location);
        mLastLocation.set(location);

        if(MainActivity.isMarkerDragged()) {

            Location markerLocation = new Location(LocationManager.GPS_PROVIDER);
            markerLocation.setLatitude(MainActivity.getMarkerLat());
            markerLocation.setLongitude(MainActivity.getMarkerLon());

            Toast.makeText(mContext, MainActivity.getMarkerLon() + " = " + MainActivity.getMarkerLat(), Toast.LENGTH_SHORT).show();

            // Current location
            distance = location.distanceTo(markerLocation);
            Toast.makeText(mContext, "marker dragged " + distance, Toast.LENGTH_SHORT).show();

        }
    }

在 onLocationChanged 方法上，我得到了这个经度和纬度

endPoint.setTitle(endPoint.getPosition().longitude + ", " + endPoint.getPosition().latitude);

这按计划工作但是当我得到服务位置时它返回 0.0(糟透了)

public static Marker endPoint;
public static boolean markerDragged = true;
public static boolean serviceStarted = false;

private static double markerLat;
private static double markerLon;

/**
 * Gets the current location of the device, and positions the map's camera.
 */
private void getDeviceLocation() {
    /*
     * Request location permission, so that we can get the location of the
     * device. The result of the permission request is handled by a callback,
     * onRequestPermissionsResult.
     */
    if (ContextCompat.checkSelfPermission(this.getApplicationContext(),
            android.Manifest.permission.ACCESS_FINE_LOCATION)
            == PackageManager.PERMISSION_GRANTED) {
        mLocationPermissionGranted = true;
    } else {
        ActivityCompat.requestPermissions(this,
                new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION);
    }
    /*
     * Get the best and most recent location of the device, which may be null in rare
     * cases when a location is not available.
     */
    if (mLocationPermissionGranted) {
        mLastKnownLocation = LocationServices.FusedLocationApi
                .getLastLocation(mGoogleApiClient);
    }

    // Set the map's camera position to the current location of the device.
    if (mCameraPosition != null) {
        mMap.moveCamera(CameraUpdateFactory.newCameraPosition(mCameraPosition));
    } else if (mLastKnownLocation != null) {
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
                new LatLng(mLastKnownLocation.getLatitude(),
                        mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));

        // Adding a marker
        endPoint = mMap.addMarker(new MarkerOptions()
                .draggable(true)
                .position(new LatLng(mLastKnownLocation.getLatitude(),
                        mLastKnownLocation.getLongitude())));
        endPoint.setTitle(getString(R.string.drag));
    } else {
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(mDefaultLocation, DEFAULT_ZOOM));
        mMap.getUiSettings().setMyLocationButtonEnabled(false);
    }
}
@Override
public void onMarkerDragEnd(Marker marker) {
    if(!serviceStarted) {
        startService(new Intent(this, LocationService.class));
    }
}

@Override
public void onMarkerDragStart(Marker marker) {
    setMarkerDragged(true);

    markerLat = marker.getPosition().latitude;
    markerLon = marker.getPosition().longitude;

    endPoint.setTitle(endPoint.getPosition().longitude + ", " + endPoint.getPosition().latitude);
}

public static double getMarkerLon(){
    return markerLon;
}

public static double getMarkerLat(){
    return markerLat;
}

Answer 1

找到解决方案:在主类上:

        Intent intent = new Intent(this, LocationService.class);
        intent.putExtra("latitude", endPoint.getPosition().latitude);
        intent.putExtra("longitude", endPoint.getPosition().longitude);
        startService(intent);

和服务:

public int onStartCommand(Intent intent, int flags, int startId)
{
    Log.e(TAG, "onStartCommand");
    super.onStartCommand(intent, flags, startId);
    markerLat = (Double) intent.getExtras().get("latitude");
    markerLon = (Double) intent.getExtras().get("longitude");
    return START_STICKY;
}