Question

I have a MediaPlayer playing a file, and I want to continuously write logging data in the background. This should be done by a Thread (or a similar concept, but I don’t know if an AsyncTask is the way to go here). The Thread shouldn’t always write, but pause for half a second in between.

My MediaPlayer works fine, but once I try to run my Thread, no video is displayed. The Thread appears to be running though.

Here’s the relevant code:

Thread:

public class LoggingThread implements Runnable {
String videoName;

public LoggingThread(String videoName) {
    Logger.startContinuousLogCSV(videoName);
    Log.d(TAG, "Created logging thread");
}

public void run() {
    Log.d(TAG, "Trying to run the thread");
    try {
        while (mIsVideoPlaying) {
            Log.d(TAG, "Video is playing. Writing rating to file.");
                    // write to file and Thread.sleep(500)
                    // problem occurs regardless of this
        }
        Log.d(TAG, "Video not playing anymore, stopping thread.");
    } catch (Exception e) {
        Logger.closeContinuousLogCSV();
    }
}
}

MediaPlayer start:

Here’s where I prepare the player for a video and create the Thread instance.

public void preparePlayerForVideo(int videoIndex) {
  Log.d(TAG, "Creating new logging thread");
  mLoggingThread = new LoggingThread(Session.sTracks.get(videoIndex));

  mPlayer = new MediaPlayer();
  // various calls to set up player, this works fine
  mPlayer.setOnPreparedListener(this);
  mPlayer.prepare();
}

This is called from the onPreparedListener.

public void startVideo() {
  mIsVideoPlaying = true;
  mLoggingThread.run();
  mPlayer.start();
}

LogCat output:

From the output, it appears that the Thread is running fine, but why is the player not showing any video?

02-15 12:00:18.904: D/SubjectivePlayerSession(17918): Creating new logging thread
02-15 12:00:18.944: D/SubjectivePlayerSession(17918): Created logging thread
02-15 12:00:18.944: D/SubjectivePlayerSession(17918): Set data source to: /mnt/sdcard/SubjectiveMovies/pair_01-video_a-GUT_DEUTSCH.mp4
02-15 12:00:19.095: V/SubjectivePlayerSession(17918): onVideoSizeChanged called
02-15 12:00:19.095: D/SubjectivePlayerSession(17918): Running thread
02-15 12:00:19.095: D/SubjectivePlayerSession(17918): Trying to run the thread
02-15 12:00:19.095: D/SubjectivePlayerSession(17918): Video is playing. Writing rating to file.
02-15 12:00:19.605: D/SubjectivePlayerSession(17918): Video is playing. Writing rating to file.
...

Answer 1

You should start a Thread object and add your Runnable to it:

public void startVideo() {
  mIsVideoPlaying = true;
  new Thread(mLoggingThread).start();
  mPlayer.start();
}

Calling Runnable#run() will run the code on the current thread, instead of creating a new one.