Android : Google map cannot load current location at first time loading

I am creating an Android application that will show the user their current location on a map. But on first time application cannot show current location marker and cannot work current location button also.i am using the following code

gps=new GPSTracker(MainActivity.this);
        if(gps.canGetLocation())
        {
            current_latitude=gps.getLatitude();
            current_longitude=gps.getLongitude();
            initialiseMap();
        }
        else
        {
        gps.showSettingsAlert();
        }





    }

    public void initialiseMap()
    {

        // check if map is created successfully or not
        if (googleMap == null) {
            Toast.makeText(getApplicationContext(),
                    "Sorry! unable to create maps", Toast.LENGTH_SHORT)
                    .show();
        }
        else
        {

        googleMap.setMyLocationEnabled(true);
        googleMap.getUiSettings().setMyLocationButtonEnabled(true);




            }