GPS reading cant be retrieved

问题:

i want to use GPS in my App. but when i tried to retrieve GPS readings as shown belwo in the code, Android studio gave me the belwo mentioned error

despit all the required permissions are added to manifest file

code:

LocationManager lm = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE);
    LocationListener ll = new LocationListener() {
        @Override
        public void onLocationChanged(Location location) {
            Log.w(TAG, "onLocationChanged");
        }

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {
            Log.w(TAG, "onStatusChanged");

        }

        @Override
        public void onProviderEnabled(String provider) {
            Log.w(TAG, "onProviderEnabled");
        }

        @Override
        public void onProviderDisabled(String provider) {
            Log.w(TAG, "onProviderDisabled");
        }
    };
    lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, ll);//error at this line

回答1:

This is due to in Marshmallow (Android version 6.0) Users can choose to turn off permissions. Simply wrap this check to see if the permission is enabled before your location code.

if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {

}

You should also write in an else statement request code which will request the permission from the user if they haven't got it.

Here's a nice request permissions method:

public void requestPermissions(List<String> permissions, ActivityCompat.OnRequestPermissionsResultCallback onRequestPermissionsResultCallback) {
    String[] params = permissions.toArray(new String[permissions.size()]);
    requestPermissions(params, onRequestPermissionsResultCallback);
}

In your case you will have to pass it the Location permissions which you can get with this method:

private List<String> getRequiredLocationPermissions() {
    String accessCoarsePermission = android.Manifest.permission.ACCESS_COARSE_LOCATION;
    String accessFineLocationPermission = android.Manifest.permission.ACCESS_FINE_LOCATION;
    int hasCoarsePermission = ContextCompat.checkSelfPermission(getActivity(), accessCoarsePermission);
    int hasFineLocationPermission = ContextCompat.checkSelfPermission(getActivity(), accessFineLocationPermission);
    List<String> permissions = new ArrayList<>();
    if (hasCoarsePermission != PackageManager.PERMISSION_GRANTED) {
        permissions.add(accessCoarsePermission);
    }
    if (hasFineLocationPermission != PackageManager.PERMISSION_GRANTED) {
        permissions.add(accessFineLocationPermission);
    }
    return permissions;
}