How to play audio in background - android

Question

I have the following code to play audio in android. I'm using Kotlin. How can I make sure the audio plays in the background once the app is closed?

// Start the media player
        playBtn.setOnClickListener {
            if (pause && mediaPlayer.isPlaying) {
                playBtn.setImageResource(R.drawable.ic_play_circle_filled);
                mediaPlayer.pause()
            } else {
                playBtn.setImageResource(R.drawable.pausebtn);

                if (pause) {
                    mediaPlayer.seekTo(mediaPlayer.currentPosition)
                    mediaPlayer.start()
                } else {
                    mediaPlayer = MediaPlayer.create(applicationContext, Uri.parse(intent.getStringExtra("audio")))
                    mediaPlayer.start()
                }
                initializeSeekBar()

                mediaPlayer.setOnCompletionListener {
                    Toast.makeText(this, "end", Toast.LENGTH_SHORT).show()
                }
            }

            pause = !pause;
        }

        prevBtn.setOnClickListener {
            try {
                mediaPlayer.seekTo(mediaPlayer.currentPosition + (-10*1000))

            } catch(e: UninitializedPropertyAccessException) {
                // media player is not initialized
            }
        }


        nextBtn.setOnClickListener {
            try {
                mediaPlayer.seekTo(mediaPlayer.currentPosition + (10*1000))
            } catch(e: UninitializedPropertyAccessException) {
                // media player is not initialized
            }
        }

        // Seek bar change listener
        seek_bar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
            override fun onProgressChanged(seekBar: SeekBar, i: Int, b: Boolean) {
                if (b) {
                    try {
                        mediaPlayer.seekTo(i * 1000)
                    } catch(e: UninitializedPropertyAccessException) {
                        // media player is not initialized
                    }
                }
            }

            override fun onStartTrackingTouch(seekBar: SeekBar) {
            }

            override fun onStopTrackingTouch(seekBar: SeekBar) {
            }
        })

Answer 1

For making the music to play in the background, you should implement the MediaPlayer API as a Service. Here is step by step guide on how you can implement the same - building a media player app

This example is in Java, hope you can understand and interpret in kotlin, else use the built in java to Kotlin converter in Android studio.