Android : currentlocation always return null value

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Android

Google-Maps

I tried to get the current location using android studio but always the variable currentLocation has null value

and the android studio draw red line under

Location currentLocation= LocationServices.FusedLocationApi.getLastLocation(mLocationclient);

and asked to check the permission I tried two ways with checking permission and without but the same result return null value

please who can help me? this is the code I have used

 private GoogleApiClient mLocationclient;
mLocationclient=new GoogleApiClient.Builder(this)
                    .addApi(LocationServices.API)
                    .addConnectionCallbacks(this)
                    .addOnConnectionFailedListener(this)
                    .build();
            mLocationclient.connect();

            Location currentLocation= LocationServices.FusedLocationApi.getLastLocation(mLocationclient);
            if(currentLocation==null)
                Toast.makeText(this,"could not connect",Toast.LENGTH_SHORT).show();
            else {
                LatLng ll=new LatLng(
                        currentLocation.getLatitude(),
                        currentLocation.getLongitude()
                );
                CameraUpdate update=CameraUpdateFactory.newLatLngZoom(ll,50);
                mMap.animateCamera(update);
            }

What I have tried:

I try (( mMap.setMyLocationEnabled(true); )) and it works fine
but programmatically does not work and always return null value to the variable currentLocation