Play Background Sound in android applications

This is tested in android studio 2.2.3

1) first copy and paste your music.mp3 into app.res.raw.

2) set service into AndroidManifest.xml be like this:

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">
    :
    :
    <service android:name=".SoundService"  android:enabled="true"></service>
</application>

3) Add SoundService.java file with contain this code:

package com.jahanweb.ring;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;

public class SoundService extends Service {
    MediaPlayer player;

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    public void onCreate() {
        player = MediaPlayer.create(this, R.raw.music); //select music file
        player.setLooping(true); //set looping
    }

    public int onStartCommand(Intent intent, int flags, int startId) {
        player.start();
        return Service.START_NOT_STICKY;
    }

    public void onDestroy() {
        player.stop();
        player.release();
        stopSelf();
        super.onDestroy();
    }

}

4) use it in the activity be like this:

package com.jahanweb.ring;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        //start service and play music
        startService(new Intent(MainActivity.this, SoundService.class));

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    protected void onDestroy() {
        //stop service and stop music
        stopService(new Intent(MainActivity.this, SoundService.class));
        super.onDestroy();
    }
}

Better to put your media code in service. It is best way to play media in background.

public class serv extends Service{

    MediaPlayer mp;
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }
    public void onCreate()
    {   
        mp = MediaPlayer.create(this, R.raw.b);
        mp.setLooping(false);
    }
    public void onDestroy()
    {       
        mp.stop();
    }
    public void onStart(Intent intent,int startid){

        Log.d(tag, "On start");
        mp.start();
    }
}

where raw is folder created in resources. and R.raw.b is an mp3 file.

MediaPlayer  player = MediaPlayer.create(this,  R.raw.music);
player.setLooping(true); // Set looping
player.setVolume(100,100);

public int onStartCommand(Intent intent, int flags, int startId) {
    player.start();
    return 1;
}

@Override
public void onDestroy() {
    player.stop();
    player.release();
}

public void onStart(Intent intent, int startId) 
{
    // TODO
}

Try below link... hope this will work

How to play audio in android using android service