全屏退出视频后，应用崩溃

Question

每次我全屏观看视频时，我都会退出该应用程序，然后返回该应用程序。它崩溃了。这是我的代码

bellow是我的错误消息

// FULL SCREEN
private void initFullScreenButton () {
    PlayerControlView controlView = playerView.findViewById(R.id.exo_controller);

    fullScreenIcon = controlView.findViewById(R.id.exo_fullscreen_icon);
    fullScreenButton = controlView.findViewById(R.id.exo_fullscreen_button);
    fullScreenButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (!playerFullScreen)
                openFullScreenDialog();
            else
                closeFullScreenDialog();
        }
    });
}

  

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“ android.view.View android.view.View.findViewById（int）”