I would like to change the Position of the map in google maps v2

But Ive done it in a TimerTask ... target, zoom, bearing and so on and it says

"IllegalStateException - not on the main thread

What should I do? Any help?

class Task extends TimerTask { 

    @Override 
    public void run() {
        CameraPosition cameraPosition = new CameraPosition.Builder()
                .target(Zt)      // Sets the center of the map to Mountain View
                .zoom(12)                   // Sets the zoom
                .bearing(180)                // Sets the orientation of the camera to east
                .tilt(30)                   // Sets the tilt of the camera to 30 degrees
                .build();                   // Creates a CameraPosition from the builder

        mMap.moveCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
    }
}

Timer timer = new Timer();

timer.scheduleAtFixedRate(new Task(), 0, 20000);