private void setFullScreen(){
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
}
private void cancelFullScreen(){
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
}
이렇게 한번 해보실래요?