CODEWITHSUNDEEP
flutter
Fidz
Fidz

Reputation: 43

Flutter MultiProvider or ChangeNotifier doesn't response

I am using MultiProvider in the main like the following:

@override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider(
          create: (context) => ReadPreferences(),
        ),
        ChangeNotifierProvider(
          create: (context) => ItemsCrud(),
        ),
      ],
      child: MaterialApp(
        initialRoute: initialPage,
        routes: {
          InitialScreen.screenId: (context) => InitialScreen(),
          HomeScreen.screenId: (context) => HomeScreen(),
          AddItemScreen.screenId: (context) => AddItemScreen(),
        },
      ),
    );
  }

But my problem is that it never read what inside ReadPreferences() class file at all, Although it reads the ItemsCrud() one normally.

My ReadPreferences() like the follwoing:

import 'package:flutter/foundation.dart'; //To use the "ChangeNotifier"
import 'package:shared_preferences/shared_preferences.dart'; //local store

class ReadPreferences extends ChangeNotifier {
  Future<SharedPreferences> _prefs = SharedPreferences.getInstance();

  //Constructor method
  ReadPreferences() {
    print('Please print this');

    getPreferences();
  }

  void getPreferences() async {
    final SharedPreferences prefs = await _prefs;
    print('print anything plz');
  }
}

It won't print anything at all, what am I doing wrong??

Upvotes: 2

Views: 376

Answers (2)

Junjie Yang
Junjie Yang

Reputation: 28

Is ReadPreferences being used in any of your child widgets(Screens)? You need to use it in your child widgets, otherwise the constructor won't be called. Used like this:

//your child widget build method
@override
  Widget build(BuildContext context) {
    ReadPreferences _dummyProvider = Provider.of<ReadPreferences>(context);
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
     .....
  }

Upvotes: 1

Loren.A
Loren.A

Reputation: 5595

I just tested this and created a test button like so that it creates an instance and fires the method in the onPressed:

FlatButton(
              child: Text('Provider Test'),
              onPressed: () {
                final readProvider =
                    Provider.of<ReadPreferences>(context, listen: false);
                readProvider.getPreferences();
              },
            ),

At first attempt I got an error : MissingPluginException (MissingPluginException(No implementation found for method getAll on channel plugins.flutter.io/shared_preferences))

Then I ran flutter clean then flutter pub get then cold restarted the app, and it works fine.

I see both print statements when I press the button.

Upvotes: 0

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