android - App stops working when mediaplayer is stopped in Service Class

Question

I am making a media player which plays music using an URL. I implemented a foreground service and also a notification. They are working fine. The problem is when I implement .stop function in media player , which is (rathu.stop)in my code, Apps gives an error displaying app stops working. I understand that I have used stop media player function in onDestroy method of service, but I dont know other place to implement that function. Then I have to set that method to a Onclicklistner also. Please help me.

Following are my codes.

MainActivity.java

package com.example.yomal.rathumakarafm;

import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.content.Context;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Build;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.Toast;

import java.io.IOException;
import java.security.Key;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {


    private SeekBar volumeSeekbar = null;

    private AudioManager audioManager = null;
    int Volume=0;

    ImageView aboutImage;
    private Button buttonStart;
    private Button buttonStop;
    private Button buttonPause;
    public static final String CHANNEL_ID = "exampleServiceChannel";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setVolumeControlStream(AudioManager.STREAM_MUSIC);
        setContentView(R.layout.activity_main);
        initControls();

        buttonStart = (Button) findViewById(R.id.buttonStart);
        buttonStop = (Button) findViewById(R.id.buttonStop);
//        buttonPause = (Button)findViewById(R.id.buttonPause);
        aboutImage = (ImageView) findViewById(R.id.about);


        buttonStart.setOnClickListener(this);
        buttonStop.setOnClickListener(this);
        aboutImage.setOnClickListener(this);

    }


    @Override
    public void onClick(View v) {


        if (v == buttonStart) {
            startService(new Intent(this, RathuMakara.class));
            buttonStart.setEnabled(false);
            buttonStop.setEnabled(true);
            Toast play = Toast.makeText(getApplicationContext(), "??? 3, 2, 1 ... ?????? ????", Toast.LENGTH_LONG);
            play.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL, 0, 0);
            play.show();


        } else if (v == buttonStop) {
            stopService(new Intent(this, RathuMakara.class));
            Toast play = Toast.makeText(getApplicationContext(), "Stopping Play", Toast.LENGTH_SHORT);
            play.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL, 0, 0);
            play.show();


            buttonStop.setEnabled(false);
            buttonStart.setEnabled(true);
        } else if (v == aboutImage)

            aboutImage = (ImageView) findViewById(R.id.about);


        aboutImage.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent aboutIntent = new Intent(MainActivity.this, AboutActivity.class);
                startActivity(aboutIntent);

            }
        });

        /*else if (v == buttonPause){
            onPause();
        }*/

    }

    private void initControls()

    {

        try {
            volumeSeekbar = (SeekBar) findViewById(R.id.sb);
            audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
            volumeSeekbar.setMax(audioManager
                    .getStreamMaxVolume(AudioManager.STREAM_MUSIC));
            volumeSeekbar.setProgress(audioManager
                    .getStreamVolume(AudioManager.STREAM_MUSIC));


            volumeSeekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
                @Override
                public void onStopTrackingTouch(SeekBar arg0) {
                    Toast volume = Toast.makeText(getApplicationContext(), "Volume: " + Integer.toString(Volume), Toast.LENGTH_SHORT);
                    volume.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL, 0, 0);
                    volume.show();

                }

                @Override
                public void onStartTrackingTouch(SeekBar arg0) {
                }

                @Override
                public void onProgressChanged(SeekBar arg0, int progress, boolean arg2) {
                    audioManager.setStreamVolume(AudioManager.STREAM_MUSIC,
                            Volume = progress , 0);
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }


    }

    public boolean onKeyDown(int keyCode, KeyEvent event){
        AudioManager audio = (AudioManager)this.getSystemService(Context.AUDIO_SERVICE);
        int currentVolume = audio.getStreamVolume(AudioManager.STREAM_MUSIC);
        if (keyCode == KeyEvent.KEYCODE_VOLUME_UP){
            volumeSeekbar.setProgress(currentVolume);
            return false;
        } else if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN){
            volumeSeekbar.setProgress(currentVolume);
            return false;
        }
        return super.onKeyDown(keyCode, event);
    }



}

Answer 1

Remove the word MediaPlayer from inside onStartCommand(). You declared a local variable with the same name as a member variable, causing the member variable to be "shadowed". That left it uninitialized, which caused an NPE in your onDestroy().