Andorid:提示开启后获取位置

Question

我想在应用程序启动时获取设备的当前位置。它工作得很好，但是如果位置被停用，它就会崩溃。所以我使用了一些代码来提示用户激活它，但似乎程序在位置被实际激活之前就到达了崩溃线。(在提示用户激活它之前)。

下面的enableLocation()方法负责提示用户和getDeviceLocation()获取位置。我尝试将getDeviceLocation()放在onstart方法中，将enableLocation()放在oncreate方法中，但仍然不起作用。有什么想法吗？

例如，在uber应用程序中，如果location被禁用，R.id.contrainer框架布局似乎会被一个虚拟片段(而不是SupportMapFragment)所取代。并且通过点击按钮来提示用户启用它。然后SupportMapFragment替换虚拟片段(根据我的理解)。但所有这些似乎都太多了。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));
} 

Answer 1

私有空getCurrentLocation() {

    gps = new GPSTracker(context, getActivity());
    if (gps.canGetLocation()) {
        if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) 
         return;
        }
        currentLatitude = gps.getLatitude();
        currentLongitude = gps.getLongitude();
    } else {
        showSettingsAlert();
    }
}