Just Audio Flutter Plugin – How to convert Duration from Stream listener to Integer?

Issue

I’m using Flutter’s Just-Audio plugin to play an mp3 file fetched from a streambuilder in my app. The streambuilder returns the duration of the file which I need for the setClip function;

player.setClip(start: Duration(milliseconds: 0), end: Duration(milliseconds: 10);

Instead of "10", the "end" point should be the file’s duration minus 500ms. So I’ve got this stream listener in my initState;

@override
  void initState() {
    super.initState();
    _init();
  }
    Future<void> _init() async {
    await player.setUrl('https://bucket.s3.amazonaws.com/example.mp3');

     player.durationStream.listen((event) {
       int newevent = event.inMilliseconds;
          });
        await player.setClip(start: Duration(milliseconds: 0), end: newevent);
     }

But I need to convert the fetched duration to an integer in order to take off 500ms. Unfortunately the int newevent = event.inMilliseconds; throws the following error;

A value of type 'int' can't be assigned to a variable of type 'Duration?'.  Try changing the type of the variable, or casting the right-hand type to 'Duration?'.

I’ve tried this;

 int? newevent = event?.inMilliseconds;

and then;

 await player.setClip(start: Duration(milliseconds: 0), end: Duration(milliseconds: newevent));

But then I just get this redline error under milliseconds: newevent ;

 The argument type 'Duration?' can't be assigned to the parameter type 'int'.

So how can I get my duration from my streamlistener as an integer so I can use it as the end point in player.setClip?

Solution

The problem appears because durationStream returns a nullable duration, and it has to be non-nullable to be able to convert it to an integer. You can promote the duration to a non-nullable type with a null check.

Furthermore, to only run setClip after the first event, use first instead of listen and move setClip inside the function:

player.durationStream.first.then((event) {
  if(event != null){
    int newevent = event.inMilliseconds - 500;
    await player.setClip(start: Duration(milliseconds: 0), end: Duration(milliseconds: newevent);
  }
});

Answered By – Hannes Hultergård

Answer Checked By – Mary Flores (FlutterFixes Volunteer)

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