Unable to get current location with google map

I'm using google map in a project, where I want to get my current location which is not working correctly,

MyActivity.java code:

 LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        boolean enabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
        if (enabled) {
            Criteria criteria = new Criteria();
            String bestProvider = locationManager.getBestProvider(criteria, true);
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.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;
            }
            Location location = locationManager.getLastKnownLocation(bestProvider);
            if (location != null) {
                lat = location.getLatitude();
                lng = location.getLongitude();
                return;
            }
        }

but it returns null every time, first i want know what's the problem and what's the best way to get my current location?

AndroidManifest.xml code

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

  <meta-data
        android:name="com.google.android.gms.version"
        android:value="@integer/google_play_services_version" />
  <meta-data
        android:name="com.google.android.geo.API_KEY"
        android:value="@string/google_maps_key" />

Use this Google Map API v2 Method

private void getCurrentLocation() {
        // Do a null check to confirm that we have not already instantiated the map.
        if (mMap == null) {
            // Try to obtain the map from the SupportMapFragment.
            mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();
            mMap.setMyLocationEnabled(true);
            // Check if we were successful in obtaining the map.
            if (mMap != null) {


             mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {

           @Override
           public void onMyLocationChange(Location arg0) {
            // TODO Auto-generated method stub

             mMap.addMarker(new MarkerOptions().position(new LatLng(arg0.getLatitude(), arg0.getLongitude())).title("It's Me!"));
           }
          });

            }
        }
    }