Freeze when playing URL with 'audioplayers' library in Flutter?

I have a list of URLs that I want to play with 'audioplayers' in Flutter. When the URL list starts to play, the freezing process occurs after playing 7-8 URLs. App and page freezes. This is always shown as an error:

E/flutter (11570): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Bad state: Future already completed
E/flutter (11570): #0      _AsyncCompleter.complete (dart:async/future_impl.dart:35:31)
E/flutter (11570): #1      AudioPlayer._completePrepared.<anonymous closure> (package:audioplayers/src/audioplayer.dart:292:29)
E/flutter (11570): #2      _RootZone.runUnaryGuarded (dart:async/zone.dart:1594:10)
E/flutter (11570): #3      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339:11)
E/flutter (11570): #4      _BufferingStreamSubscription._add (dart:async/stream_impl.dart:271:7)
E/flutter (11570): #5      _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:123:11)
E/flutter (11570): #6      _MapStream._handleData (dart:async/stream_pipe.dart:218:10)
E/flutter (11570): #7      _RootZone.runUnaryGuarded (dart:async/zone.dart:1594:10)
E/flutter (11570): #8      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339:11)
E/flutter (11570): #9      _BufferingStreamSubscription._add (dart:async/stream_impl.dart:271:7)
E/flutter (11570): #10     _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:123:11)
E/flutter (11570): #11     _WhereStream._handleData (dart:async/stream_pipe.dart:195:12)
E/flutter (11570): #12     _RootZone.runUnaryGuarded (dart:async/zone.dart:1594:10)
E/flutter (11570): #13     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339:11)
E/flutter (11570): #14     _DelayedData.perform (dart:async/stream_impl.dart:515:14)
E/flutter (11570): #15     _PendingEvents.handleNext (dart:async/stream_impl.dart:620:11)
E/flutter (11570): #16     _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:591:7)
E/flutter (11570): #17     _microtaskLoop (dart:async/schedule_microtask.dart:40:21)
E/flutter (11570): #18     _startMicrotaskLoop (dart:async/schedule_microtask.dart:49:5)

My related codes are as follows:

  bool isPlaying = false;
AudioPlayer audioPlayer = AudioPlayer();
int currentIndex = 0;
int start = 0;
...
//button pressed
onPressed: () {
isPlaying = !isPlaying;
if (start == 0) {
start++;
playAudioInstructions();
} else if (start == 1) {
start++;
audioPlayer.pause();
} else {
start--;
audioPlayer.resume();
}
setState(() {});
},
...
void playAudioInstructions() {
playAudio(urlList, currentIndex);
}
Future<void> playAudio(List<String> urlList, int currentIndex) async {
await audioPlayer.play(UrlSource(urlList[currentIndex]));
audioPlayer.onPlayerComplete.listen((event) {
if (currentIndex < urlList.length - 1) {
audioPlayer.stop();
currentIndex++;
playAudio(urlList, currentIndex);
} else {
currentIndex = 0;
audioPlayer.stop();
start = 0;
}
});
}
...

I couldn't figure out the cause of the freezing. I'd be happy to get help with the code snippet.

The freezing issue you're experiencing seems to be related to the "Bad state: Future already completed" error in your Flutter app. This error typically occurs when you try to complete a Future that has already been completed.

Looking at your code, the issue seems to be happening in the playAudio function when you recursively call playAudio to play the next URL in the list. The problem arises because you're not properly canceling the previous audioPlayer.onPlayerComplete subscription before creating a new one. As a result, multiple subscriptions are created, leading to the error.

To fix this issue, you need to cancel the previous subscription using the cancel method before creating a new subscription. Here's an updated version of your code with the necessary modifications:

bool isPlaying = false;
AudioPlayer audioPlayer = AudioPlayer();
int currentIndex = 0;
int start = 0;
StreamSubscription<void>? playerCompleteSubscription; // Add this line
// ...
onPressed: () {
isPlaying = !isPlaying;
if (start == 0) {
start++;
playAudioInstructions();
} else if (start == 1) {
start++;
audioPlayer.pause();
} else {
start--;
audioPlayer.resume();
}
setState(() {});
},
// ...
void playAudioInstructions() {
playAudio(urlList, currentIndex);
}
Future<void> playAudio(List<String> urlList, int currentIndex) async {
await audioPlayer.play(UrlSource(urlList[currentIndex]));
playerCompleteSubscription?.cancel(); // Cancel previous subscription if exists
playerCompleteSubscription = audioPlayer.onPlayerComplete.listen((event) {
if (currentIndex < urlList.length - 1) {
audioPlayer.stop();
currentIndex++;
playAudio(urlList, currentIndex);
} else {
currentIndex = 0;
audioPlayer.stop();
start = 0;
}
});
}

In the updated code, I added a StreamSubscription<void>? playerCompleteSubscription variable to keep track of the subscription for audioPlayer.onPlayerComplete events. Before creating a new subscription, I check if there is an existing subscription and cancel it using the cancel method.

By canceling the previous subscription, you ensure that only one subscription is active at a time, preventing the "Bad state: Future already completed" error and potential freezing of the app.

Make sure to replace the corresponding sections in your original code with the modified code provided above.