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How to stop mediaplayer while playing on background?

I am developing a music player on android and the app has two activities (MainActivity and PlayActivity). In the MainActivity I have a listview with a list of songs and in the PlayActivity I have a button to listen and pause the music. The problem is that when go back to MainActivity and I select a new song from the listview, the first one keeps playing on background while the second one also starts playing. How can I stop the first song when I select a new one?
(I don't want to stop mediaplayer onBackPressed, I just want to stop the music when another song it's selected from listview and play a fresh song in PlayActivity)
EDIT: I'm using AsyncTask to start mediaplayer on PlayActivity: mp.prepareAsync();

You could try to stop MediaPlayer when onBackPressed()
MediaPlayer mp ; // mp is your MediaPlayer
#Override
public void onBackPressed() {
if (mp != null) {
mp.stop();
mp.release();
mp = null;
}
super.onBackPressed();
}

private void playMusic() {
if (mp != null) {
if (mp.isPlaying()) {
mp.stop();
mp.release();
MediaPlayer copyMp = new MediaPlayer();
try {
copyMp.setDataSource("/path");
mp = copyMp;
mp.prepare();
mp.start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

From here
MediaPlayer is not thread-safe. Creation of and all access to player
instances should be on the same thread.
That means you have to maintain one media player instance throughout your whole application(As per your requirement). I don't know how you implemented the media player(Service/AsyncTask etc.). When you select a new song, you need to access that instance and replace the existing song with the selected one.

Checking the Media player

If i am playing song from a song list and if the other song is already playing then both songs plays simultaneously in android studio. If i just use next or previous buttons then they are working fine. The problem is through song list. I am not getting how to check if media player is playing already or not in this condion. I am doing this code in kotlin and i am new user of android studio.

you can check this way
You can take a global variable of MediaPlayer
public MediaPlayer mediaPlayer;
and then create in onCreate method:
mediaPlayer= MediaPlayer.create(this, R.raw.xxxx);
and thus your play method will be:
public void mediaPlay(View view) {
if(mediaPlayer.isPlaying()) {
mediaPlayer.stop();
}
else{
mediaPlayer.setLooping(true);
mediaPlayer.start();
}
}

Android Media Player Release won't stop playing

Here's my scenario:
I have a timer that counts down from 20 seconds. At 13 seconds, a sound starts playing. At 0 seconds, I stop the current sound, load up a new sound and play that new sound. Once that sounds finishes, I load up the previous sound, set it to loop, and start it.
This is the logic for hitting 0 seconds:
mp.stop();
mp = MediaPlayer.create(mActivity, R.raw.second_sound);
mp.start();
mp.setOnCompletionListener(new OnCompletionListener() {
#Override
public void onCompletion(MediaPlayer mp) {
mp = MediaPlayer.create(mActivity, R.raw.first_sound);
mp.setLooping(true);
mp.start();
}
});
Once the last sound starts playing, calling mp.release() doesn't stop the player. Any ideas as to how to stop the player?
Note: mp.release() works during the first time I start playing and during the second sound but not during the looping sound.
Solution: My global MediaPlayer is also named "mp". Oops.

You're getting the mp MediaPlayer objects mixed up a little. If mp.release() is being called outside of the onCompletion() method, it is not referring to the looping instance created there. Change the identifiers in onCompletion() to refer to the "outer" mp. For example, if your code is in MainActivity:
mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener()
{
#Override
public void onCompletion(MediaPlayer mp)
{
MainActivity.this.mp = MediaPlayer.create(MainActivity.this, R.raw.chirp);
MainActivity.this.mp.setLooping(true);
MainActivity.this.mp.start();
}
}
);

Why are you creating new media player every time and not releasing old one onCompltion? did you try setDataSource?

Lag between two sound "Mediaplayer" android

I want to play two sounds. I'm using this code but there's lag between the two sounds for about 2s. I want to play the second directly when the first sound is finished. How can I do that?
MediaPlayer mp = MediaPlayer.create(getApplicationContext(),R.raw.s83);
mp.start();
mp.setOnCompletionListener(new OnCompletionListener() {
public void onCompletion(MediaPlayer mp2){
mp2 = MediaPlayer.create(getApplicationContext(),R.raw.ss);
mp2.start();
}
});

Android 4.1 (v16) adds MediaPlayer.setNextMediaPlayer which was added to allow gapless playing as per the feature list. Prior to that, there is always a small delay between onCompletion and starting another MediaPlayer due to buffering. Creating the second MediaPlayer before onCompletion might help as well (and would be required for using setNextMediaPlayer anyways).

Try this:
Make mp2 a MediaPlayer class field and then use this code:
mp2 = MediaPlayer.create(getApplicationContext(),R.raw.ss);
MediaPlayer mp = MediaPlayer.create(getApplicationContext(),R.raw.s83);
mp.start();
mp.setOnCompletionListener(new OnCompletionListener() {
public void onCompletion(MediaPlayer mp){
YourActivityClass.this.mp2.start();
}
});
It will at least create the second MediaPlayer object and prepare() before the first sound is played, so you gain some time there.

Android: Playing two sounds one after the other

I am trying to play two sound items, one after the other
MediaPlayer mp = null;
protected void produceErrorSound(int index) {
if (mp != null) {
mp.reset();
mp.release();
}
mp = MediaPlayer.create(this, index);
mp.start();
}
public void correctAnswerAndNext(){
produceErrorSound(R.raw.right1) ;
produceErrorSound(R.raw.right1) ;
}
but only second sound is produced.
is there any alternative approach?

I can't see any wait mechanism in your code.
You can use an onCompletionListener to receive a callback when your first MediaPlayer has finished playback. At that point you can start the second MediaPlayer.
An alternative way in Jellybean (and later versions) is to use the audio chaining functionality (i.e. setNextMediaPlayer) to automatically start another MediaPlayer as soon as the current one has finished playing. Something like this (I've omitted the calls to setDataSource etc for brevity):
mediaPlayer1.prepare();
mediaPlayer2.prepare();
mediaPlayer1.start();
mediaPlayer1.setNextMediaPlayer(mediaPlayer2);