Making a Singleton Class in Android

Question

I'm trying to make a simple mp3 player app for a project and I'm having trouble with accessing the service from the main activity. I have some onclicklisteners in the activity:

play.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            Intent intent = new Intent(getApplicationContext(), PlayService.class);
            intent.putExtra("key", 0);
            startService(intent);               
        }
    });

    pause.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            Intent intent = new Intent(getApplicationContext(), PlayService.class);
            intent.putExtra("key", 1);
            startService(intent);
        }
    });

    stop.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            Intent intent = new Intent(getApplicationContext(), PlayService.class);
            intent.putExtra("key", 2);              
        }
    });

and a switch statement in my service that responds to the onclicks:

@Override
public int onStartCommand(Intent intent, int flags, int startId){

    int key = intent.getIntExtra("key", 1);
    MediaPlayer mMediaPlayer = new MediaPlayer();

    FileInputStream fileStream = null;
    try {
        fileStream = new FileInputStream("/sdcard/Download/Bob_Marley-Jammin.mp3");
    }
    catch (FileNotFoundException e1) {
            e1.printStackTrace();
    }

    switch (key) {
    case 0: //Play
        if (mMediaPlayer.isPlaying()){
            break;
        }
        else
            try {
                mMediaPlayer.setDataSource(fileStream.getFD());
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalStateException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            try {
                mMediaPlayer.prepare();
            } catch (IllegalStateException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            mMediaPlayer.start();
        break;
    case 1: //Pause
            mMediaPlayer.pause();
        break;
    case 2: //Stop
        if(mMediaPlayer.isPlaying()){
            mMediaPlayer.pause();
            mMediaPlayer.seekTo(0);
        }
        break;
    default:
        break;
    }   

    return Service.START_NOT_STICKY;
}

For some reason the play call works but the pause and stop calls have no effect. I think this might be because I'm creating a new MediaPlayer reference each time I'm calling the service. (I'm not sure how to fix this)

So I've heard it's easier to access the service by making it a singleton class and accessing it from the activity but I'm not sure how to implement that. Any tips based off my code?

Yes I have. I know the basic syntax but I'm having trouble implementing it — Connor Black, Jun 13 '12 at 02:11
The book "Effective Java" shows you how to create a good singleton class. I use Roboguice and @Singleton, which is more concise. — Christine, Jun 13 '12 at 07:32

score 0 · Accepted Answer · answered Jun 13 '12 at 02:15

The startService in the play button starts your service. Every next button click tries to start the service again, which will have no effect. You'll have to bind to the service, and set up communication between your activity and the service, in order for stop and pause to work. Put "play" in a call also. There's good documentation on how communication between activities and services work here: http://developer.android.com/reference/android/app/Service.html

score 0 · Answer 2 · edited May 23 '17 at 12:12

0

You can't init Service (use constructor, or call getInstance method), so you can't use singleton class.
The solution is you can communicate between your activity and service. Here is an Example: Communication between Activity and Service using Messaging
Look local service sample in android doc: http://developer.android.com/reference/android/app/Service.html

edited May 23 '17 at 12:12

Community

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answered Jun 13 '12 at 02:22

ductran

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Making a Singleton Class in Android

2 Answers2