Setting up an AnimationListener for an ObjectAnimator

Since you implemented AnimatorListener in your MainActivity, you must include all its abstract methods, and change nAnim.addListener(new Animat.... to nAnim.addListener(this)

@Override
public void onAnimationStart(Animator animation){
}

@Override
public void onAnimationEnd(Animator animation){
    startGame(level)
}

@Override
public void onAnimationRepeat(Animator animation){
}

@Override
public void onAnimationCancel(Animator animation){
}