为什么在观看重新设置的视频广告之后重启应用？

Question

我在活动开始时显示广告，应用程序已发布且一切正常但在用户观看奖励视频广告然后关闭应用程序后，某些手机上的应用程序重新启动（我不确定它是否真的重新启动，但它导致他回到主要的第一个活动）

这是我的代码：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_quiz_1);
        MobileAds.initialize(this,"ca-app-pub-6995305968327976~6090393454");
        mad = MobileAds.getRewardedVideoAdInstance(this);
        mad.setRewardedVideoAdListener(this);
        mad.loadAd("ca-app-pub-6995305968327976/4158310785",new AdRequest.Builder().build());

这是onRewardedVideoAdLoaded()方法：

@Override
    public void onRewardedVideoAdLoaded() {
        LinearLayout everything;
        everything = (LinearLayout) findViewById(R.id.everything);
        everything.setVisibility(View.VISIBLE);
        if(!QuizActivity.this.isFinishing()){
            AlertDialog.Builder builder =  new AlertDialog.Builder(QuizActivity.this);
            builder.setTitle("...");
            builder.setMessage("...");
            builder.setCancelable(false);

            builder.setPositiveButton("...", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    if(mad.isLoaded()){
                        mad.show();
                    }
                }
            });

            builder.setNegativeButton("..", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });
            AlertDialog alert = builder.create();
            alert.show();
            GifImageView load;
            load = (GifImageView) findViewById(R.id.load);
            load.setVisibility(View.GONE);
        }
    }