import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;
import android.provider.Settings;
import android.widget.Toast;

public class backgroud_demo extends Service {

    private MediaPlayer mplayer;


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

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        mplayer = MediaPlayer.create(this,
                R.raw.iphone);
        mplayer.setLooping(true);
        mplayer.start();
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mplayer.stop();
    }
}

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity implements View.OnClickListener  {

    Button play,stop1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        play = (Button) findViewById(R.id.btn1);

        stop1 = (Button) findViewById(R.id.btn3);
        play.setOnClickListener(this);
        stop1.setOnClickListener(this);

    }
    @Override
    public void onClick(View view) {
        if (view == play) {
            startService(new Intent(this, backgroud_demo.class));

        } else if (view == stop1) {
            stopService(new Intent(this, backgroud_demo.class));

        }
    }


}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="PLAY" android:layout_marginTop="30dp"
        android:layout_marginLeft="30dp"
        android:layout_marginRight="30dp"
        />

    <Button
        android:id="@+id/btn3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="STOP" android:layout_marginTop="40dp"
        android:layout_marginLeft="30dp"
        android:layout_marginRight="30dp" />

</LinearLayout>

Add below line in AndroidManifest.xml

                                  <service android:name=".backgroud_demo" />
                                   

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