convert StreamBuilder to StreamProvider

Question

I have a StreamBuilder like this:

StreamBuilder<List<AuthInfo>>(
            stream: myDatabase.authInfosDao.watch(),
            builder: (context, snapshot) => (snapshot.data?.length ?? 0) > 0
                ? Home()
                : Auth()),

and I want to redo it into a Stream Provider and that's what happened:

StreamProvider<List<AuthInfo>>.value(
            value: myDatabase.authInfosDao.watch(),
            initialData: [],
            builder: (BuildContext context, AsyncSnapshop snapshot)...

and I can't figure out how to use the data that came in "Value" to load the desired page since there is no snapshot in StreamProvider

Answer 1

The StreamProvider will rebuild the widget every time new data arrives on the stream. It functions similar to ChangeNotificationProvider which does not generate a new change put updates data that the provider is listen on.

dependencies:
  flutter:
    sdk: flutter
  provider: ^6.0.2

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(
    const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return
    StreamProvider<ModelObject>(
      initialData: ModelObject(value:0),
      create:(_)=>createStream(),
      child:  MaterialApp(
        home: Test_StreamProviderWidget(),
      ));
    
  }
}

class ModelObject{

  ModelObject({this.value});
  int ? value;
}
Stream<ModelObject> createStream(){
  return 
  Stream<ModelObject>.periodic( Duration(seconds:1), (currentPeriodicValue)=>ModelObject(value:currentPeriodicValue+1)).take(10000);
}

class Test_StreamProviderWidget extends StatefulWidget {
  Test_StreamProviderWidget({Key? key}) : super(key: key);

  @override
  State<Test_StreamProviderWidget> createState() => _Test_StreamProviderWidgetState();
}

class _Test_StreamProviderWidgetState extends State<Test_StreamProviderWidget> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(appBar: AppBar(title:Text("stream provider")),body:
    Consumer<ModelObject>(
      builder:(context, model, child) {
        return 
        Center(child:Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
        
        Text('${model.value.toString()}',style: Theme.of(context).textTheme.headline2,)

        ],));
        
      },
    
    )
    )
    ;
  }
}