Android MediaPlayer unexpectedly stops playback (without being finalized)

I just stumbled across problem with it's this not-so-obvious solution and thought it might be helpful to some if I share my findings.

There are lots of similar questions but they didn't help me solve mine. (are different)

I have a activity that plays a video with sound, then displays an image for 3 seconds, then displays an animated mapview for 10 seconds and then plays another video.

• video1 (~60sec)
• image (~3sec)
• animated mapview (~10sec)
• video2 (~30sec)

the arose when trying to play audio from the moment the first video finished.
the audio played fine for the duration of the mapview, then stopped.
I tried all sorts of scenarios but the music always stopped when something changed, although some combinations worked (e.g. without map and video2 (just blackscreen instead)).
I did take a very close look at all the logs but didnt find anything helpful.

The issue is not that the mediaplayer is being gc'd or finalized somehow before finishing.

private static MediaPlayer mediaplayer;

and in OnCreate:

    mediaplayer = new MediaPlayer();
    AudioFocusRequest.Builder mp;
    mediaplayer.setAudioAttributes(
            new AudioAttributes
                    .Builder()
                    .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                    .build());
    try {
        mediaplayer.setDataSource(getApplicationContext(), Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.audio));
    } catch (IOException e) {
        e.printStackTrace();
        Log.e("audio_management","error trying to set data source for audio");
    }
    try {
        mediaplayer.prepare();
    } catch (IOException e) {
        e.printStackTrace();
        Log.e("audio_management","error preparing");
    }

Here's an example of how I play the videos

        z.schedule(new TimerTask() {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {

                @Override
                public void run() {
                    playPart2();
                }
            });
        }
    }, PARTONELENGTH + MAPDISPLAYTIME + IMAGEDISPLAYTIME);

and this is the playPart2() function:

    public void playPart2() {
    ImageView imgbg =  findViewById(R.id.imageView);
    ImageView agO = findViewById(R.id.agent1);
    ImageView agTw =  findViewById(R.id.agent2);
    ImageView agTh =  findViewById(R.id.agent3);
    ImageView agFo =  findViewById(R.id.agent4);
    ImageView agFi =  findViewById(R.id.agent5);
    ImageView agSi = findViewById(R.id.agent6);
    VideoView player =  findViewById(R.id.videoView);
    MapView mMap = findViewById(R.id.map);

    mMap.setVisibility(View.INVISIBLE);
    imgbg.setVisibility(View.INVISIBLE);
    agO.setVisibility(View.INVISIBLE);
    agTw.setVisibility(View.INVISIBLE);
    agTh.setVisibility(View.INVISIBLE);
    agFo.setVisibility(View.INVISIBLE);
    agFi.setVisibility(View.INVISIBLE);
    agSi.setVisibility(View.INVISIBLE);
    player.setVisibility(View.VISIBLE);


    Uri uri = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.part2);
    player.setVideoURI(uri);
    player.start();
}

I really dont know what is going on - I 've read through all the documentation concerning MediaPlayer and VideoViews. It says that it is possible to output 2 streams of audio at the same time. But it doesnt work.

turns out the videoView starting playback somehow paused the mediaplayer.
what solved the problem was just calling mediaplayer.start() again. it did resume where it had stopped all the times before. the (apparently existing) short break in playback is not noticeable.

why is this behaviour of mediaplayer/videoview not mentioned anywhere?

issue-solving-code:

        z.schedule(new TimerTask() {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {

                @Override
                public void run() {
                    playPart2();
                    mediaplayer.start();
                }
            });
        }
    }, PARTONELENGTH + MAPDISPLAYTIME + IMAGEDISPLAYTIME);