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I'm trying to use an Inherited Widget to share the same service across all the screens.

This is the code of my Inherited Widget: 

class GlobalValues extends InheritedWidget {
  final AudioProvider audioProvider;

  GlobalValues({Key key, Widget child, this.audioProvider}) : super(key: key, child: child);

  static AudioProvider of(BuildContext context){
    return (context.dependOnInheritedWidgetOfExactType<GlobalValues>()).audioProvider;
  }

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) {
    return false;
  }
}

Therefore, I initialize it in the Home Screen: 

@override
  Widget build(BuildContext context) {
    double width = MediaQuery.of(context).size.width;

    return GlobalValues(
      audioProvider: AudioProvider(),
      child: StreamBuilder<MapEntry<Position, List<MuseumCard>>>(...)
    );
  }

and finally I would like to access it from a subsequent screen: 

@override
  Widget build(BuildContext context) {
    super.build(context);
    AudioProvider audioProvider = GlobalValues.of(context);
    Return Scaffold(...);
  }

But when the last screen is built I got this error message:

The getter 'audioProvider' was called on null. Receiver: null Tried calling: audioProvider

I'm noticing that if I initialize the widget in the main.dart then the error doesn't show up and everything works correctly: 

@override
  Widget build(BuildContext context) {
    return GlobalValues(
      audioProvider: AudioProvider(),
      child: MaterialApp(...),);
  }

But I would like to make it available only in a certain part of widget subtree, but don't know why it doesn't work.

Could it be due to routing between the screens? Or what other reason?

Thank you

Matteo Zantedeschi
  • 35
  • 5

1 Answers1

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Change you code while accessing as follow. You are missing to call audioProvider member of the class.

  @override
  Widget build(BuildContext context) {
    super.build(context);
    AudioProvider audioProvider = GlobalValues.of(context).audioProvider;
    Return Scaffold(...);
  }
Dilip Sharma
  • 41
  • 1
  • 6