Android App Architecture: Implements user permission in lifecycle

Question

I have a LocationListener which is extended LiveData Class. From the Android 6.0, the permission is requested in runtime. Now , when I tried to implements the LiveData Class and it required the permission checking in onActive() function. I have to make the boilerplate code in each activity for the permission requested and result received. Is there any way to move such onRequestPermissionsResult() and checkSelfPermission() functions to the LocationListener ?

LocationFragment.java

public class LocationFragment extends LifecycleFragment {

  private FragmentLocationBinding binding;


  public LocationFragment() {
    // Required empty public constructor
  }


  @Override
  public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    if (ContextCompat.checkSelfPermission(getActivity(),
        permission.ACCESS_COARSE_LOCATION)
        != PackageManager.PERMISSION_GRANTED) {
      // Should we show an explanation?
      if (ActivityCompat.shouldShowRequestPermissionRationale(getActivity(),
          Manifest.permission.ACCESS_COARSE_LOCATION)) {
        // Show an explanation to the user *asynchronously* -- don't block
        // this thread waiting for the user's response! After the user
        // sees the explanation, try again to request the permission.

      } else {

        // No explanation needed, we can request the permission.

        ActivityCompat.requestPermissions(getActivity(),
            new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
            200);

        // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
        // app-defined int constant. The callback method gets the
        // result of the request.
      }
    }
    //get the viewmodel from activity
    LastLocationViewModel lastLocationViewModel = ViewModelProviders.of(getActivity())
        .get(LastLocationViewModel.class);
    lastLocationViewModel.getLastKnowLocation().observe(this, location -> {
      binding.setLocation(location);
    });

  }

  @Override
  public void onRequestPermissionsResult(int requestCode,
      String permissions[], int[] grantResults) {
    switch (requestCode) {
      case 200: {
        // If request is cancelled, the result arrays are empty.
        if (grantResults.length > 0
            && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
          Toast.makeText(getActivity(), "Rights Granted", Toast.LENGTH_SHORT).show();
          // permission was granted, yay! Do the
          // contacts-related task you need to do.
        } else {
          // permission denied, boo! Disable the
          // functionality that depends on this permission.
        }
        return;
      }

      // other 'case' lines to check for other
      // permissions this app might request
    }
  }

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
      Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    binding = DataBindingUtil
        .inflate(LayoutInflater.from(getActivity()), R.layout.fragment_location, null, false);
    return binding.getRoot();
  }

}

LastLocationListener.java

public class LastLocationListener extends LiveData<Location> {

  private LocationManager locationManager;

  private Context context;

  private LocationListener listener = new LocationListener() {
    @Override
    public void onLocationChanged(Location location) {

      Log.d("Location Msg", location.toString());
      setValue(location);
    }

    @Override
    public void onStatusChanged(String s, int i, Bundle bundle) {

    }

    @Override
    public void onProviderEnabled(String s) {

    }

    @Override
    public void onProviderDisabled(String s) {

    }
  };

  public LastLocationListener(Context context) {
    this.context = context;
    locationManager = (LocationManager) context.getSystemService(
        Context.LOCATION_SERVICE);
  }

  @Override
  protected void onActive() {
    if (ActivityCompat.checkSelfPermission(context, permission.ACCESS_FINE_LOCATION)
        != PackageManager.PERMISSION_GRANTED
        && ActivityCompat.checkSelfPermission(context, permission.ACCESS_COARSE_LOCATION)
        != PackageManager.PERMISSION_GRANTED) {
      // TODO: Consider calling
      //    ActivityCompat#requestPermissions
      // here to request the missing permissions, and then overriding
      //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
      //                                          int[] grantResults)
      // to handle the case where the user grants the permission. See the documentation
      // for ActivityCompat#requestPermissions for more details.
      return;
    }
    locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, listener);
  }

  @Override
  protected void onInactive() {
    locationManager.removeUpdates(listener);
  }


}

Answer 1

when I tried to implements the LiveData Class and it required the permission checking in onActive() function

No, it does not. What you are seeing is a Lint warning, which you can suppress. What is required is that you hold the permission before attempting to use this particular bit of LiveData.

Is there any way to move such onRequestPermissionsResult() and checkSelfPermission() functions to the LocationListener ?

No.