Android Video View位于另一个Video View的顶部，但透明的顶部Video View无法加载视频

Question

我正在使用VideoView播放视频。在视频的中间暂停该视频，并在该VideoView上方加载该Frame Layout内的Frame Layout并具有另一个VideoView。在该顶部VideoView流中，另一个视频却无法正常工作，第二个VideoView是透明的，请参见底部VideoView。

这是我用于调试的xml，为Framelayout提供了绿色背景。

    <LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="320dp">
        <VideoView
            android:id="@+id/videoView"
            android:layout_width="match_parent"
            android:layout_centerInParent="true"
            android:layout_height="300dp"
            android:contentDescription="@string/app_name"
            />

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="300dp"
            android:src="@drawable/ic_launcher_background"
            android:layout_alignParentEnd="true"
            android:layout_centerVertical="true"
            android:id="@+id/imageView"
            android:visibility="gone"
            android:background="#f2f2">
            <VideoView
                android:id="@+id/videoOver"
                android:layout_width="match_parent"
                android:layout_centerInParent="true"
                android:layout_height="250dp"
                android:contentDescription="@string/app_name"
                />
        </FrameLayout>
    </RelativeLayout>



    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"/>

</LinearLayout >

这是我的Java代码

    public class MainActivity extends AppCompatActivity {
    boolean running = false;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final VideoView mVideoView = findViewById(R.id.videoView);
        final VideoView mVideoOver = findViewById(R.id.videoOver);

        final TextView text = findViewById(R.id.textView);
        final FrameLayout overLay = findViewById(R.id.imageView);
        mVideoView.setVideoURI(Uri.parse("https://ia600201.us.archive.org/22/items/ksnn_compilation_master_the_internet/ksnn_compilation_master_the_internet_512kb.mp4"));
        mVideoView.requestFocus();
        mVideoView.start();

        mVideoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mediaPlayer) {
                running = true;
                final int duration = mVideoView.getDuration();

                new Thread(new Runnable() {
                    public void run() {
                        do{
                            text.post(new Runnable() {
                                public void run() {
//                                    int time = (duration - mVideoView.getCurrentPosition())/1000;
                                    int time = (mVideoView.getCurrentPosition())/1000;
                                    if(time == 15){
                                        mVideoView.pause();
                                        overLay.setVisibility(View.VISIBLE);
                                        mVideoOver.setVideoURI(Uri.parse("http://techslides.com/demos/sample-videos/small.mp4"));
                                        mVideoView.clearFocus();
                                        mVideoOver.requestFocus();
                                        mVideoOver.start();
                                    }
                                    text.setText(time+"");
                                }
                            });
                            try {
                                Thread.sleep(500);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            if(!running) break;
                        }
                        while(mVideoView.getCurrentPosition()<duration);
                    }
                }).start();
            }
        });
    }
}