ANDROID:在提示用户启用位置后获取该位置

我想在应用程序启动时获取设备的当前位置。它工作正常,但如果禁用该位置,则会崩溃。因此,我使用了一些代码来提示用户激活它,但似乎程序在实际激活位置之前就到达了崩溃线(在提示用户激活它之前)。

例如,在uber应用程序中,如果位置被禁用,R.id.container框架布局似乎会被虚拟片段(而不是SupportMapFragment)替换。点击一个按钮,提示用户启用它。然后SupportMapFragment将替换虚拟片段(据我所知)。但这一切似乎太过分了。这是唯一的办法吗?

oncreate() {
....
    SupportMapFragment fragment;
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragment = new SupportMapFragment();
    fragmentManager.beginTransaction().replace(R.id.container, fragment).commit();
    fragment.getMapAsync(this);
..... 
}

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

    // Prompt the user for permission.
    getLocationPermission();

    // Prompt the user to enable location if it is disabled
    // by using Task<LocationSettingsResponse>
    // and LocationSettingsRequest.Builder
    enableLocation();

    // Turn on the My Location layer and the related control on the map.
    updateLocationUI();

    // Get the current location of the device and set the position of the map.
    // uses Task.getResult which returns null because location
    // is yet to be activated despite chosing to do so above
    getDeviceLocation();
}

// inside getDeviceLocation();
@Override
public void onComplete(@NonNull Task<Location> task) {
       if (task.isSuccessful()) {
                // Set the map's camera position to the current location of the device.
                mLastKnownLocation = task.getResult(); // RETURNS NULL HERE
                mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
                new LatLng(mLastKnownLocation.getLatitude(),
                LastKnownLocation.getLongitude()), DEFAULT_ZOOM));
}