Detail tentang paket Penyedia untuk Flutter

1. StatefulWidget

class _MyWidgetState extends State<MyWidget> {
  DateTime _time = DateTime.now();  @override
  Widget build(BuildContext context) {
    return FlatButton(
      child: Text(_time.toString()),
      onPressed: () {
        setState(() => _time = DateTime.now());
      },
    );
  }
}

2. Warisan Warisan

3. ScopedModel

class MyModel extends Model {
  String _foo;  String get foo => _foo;
  
  void set foo(String value) {
    _foo = value;
    notifyListeners();  
  }
}

ScopedModel<MyModel>(
  model: MyModel(),
  child: MyApp(...)
)

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ScopedModelDescendant<MyModel>(
      builder: (context, child, model) => Text(model.foo),
    );
  }
}

class OtherWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FlatButton(
      child: Text('Update'),
      onPressed: () {
        final model = ScopedModel.of<MyModel>(context);
        model.foo = 'bar';
      },
    );
  }
}

4. BLoC

class MyBloc {
  final _controller = StreamController<MyType>();  Stream<MyType> get stream => _controller.stream;
  StreamSink<MyType> get sink => _controller.sink;
  
  myMethod() {
    //  
    sink.add(foo);
  }  dispose() {
    _controller.close();
  }
}
 ,   BLoC:
@override
Widget build(BuildContext context) {
 return StreamBuilder<MyType>(
  stream: myBloc.stream,
  builder: (context, asyncSnapshot) {
    //  
 });
}

5. Penyedia

• Penyedia Dasar
• ChangeNotifierProvider
• StreamProvider
• Futureprovider
• ValueListenableProvider
• MultiProvider
• Proxyprovider

Instalasi

Provider<MyModel>(
  builder: (context) => MyModel(),
  child: MyApp(...),
)

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Consumer<MyModel>(
      builder: (context, value, child) => Text(value.foo),
    );
  }
}

class OtherWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FlatButton(
      child: Text('Update'),
      onPressed: () {
        final model = Provider.of<MyModel>(context);
        model.foo = 'bar';
      },
    );
  }
}

class MyModel with ChangeNotifier {
  String _foo;  String get foo => _foo;
  
  void set foo(String value) {
    _foo = value;
    notifyListeners();  
  }
}

ChangeNotifierProvider<MyModel>(
  builder: (context) => MyModel(),
  child: MyApp(...),
)

final model = Provider.of<MyModel>(context);

final model = Provider.of<MyModel>(context, listen: false);

@override
Widget build(BuildContext context {
  return StreamBuilder(
   stream: FirebaseAuth.instance.onAuthStateChanged, 
   builder: (BuildContext context, AsyncSnapshot snapshot){ 
     ...
   });
}

StreamProvider<FirebaseUser>.value(
  stream: FirebaseAuth.instance.onAuthStateChanged,
  child: MyApp(...),
}

@override
Widget build(BuildContext context) {
  return Consumer<FirebaseUser>(
    builder: (context, value, child) => Text(value.displayName),
  );
}

FutureProvider<FirebaseUser>.value(
  value: FirebaseAuth.instance.currentUser(),
  child: MyApp(...),
);

class MyModel {
  final ValueNotifier<int> counter = ValueNotifier(0);  
}

Provider<MyModel>(
  builder: (context) => MyModel(),
  child: Consumer<MyModel>(builder: (context, value, child) {
    return ValueListenableProvider<int>.value(
      value: value.counter,
      child: MyApp(...)
    }
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Consumer<int>(
      builder: (context, value, child) {
        return Text(value.toString());
      },
    );
  }
}

class OtherWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FlatButton(
      child: Text('Update'),
      onPressed: () {
        final model = Provider.of<MyModel>(context);
        model.counter.value++;
      },
    );
  }
}

Provider<Foo>.value( 
  value: foo, 
  child: Provider<Bar>.value( 
    value: bar, 
    child: Provider<Baz>.value( 
      value: baz , 
      child: MyApp(...)
    ) 
  ) 
)

MultiProvider( 
  providers: [ 
    Provider<Foo>.value(value: foo), 
    Provider<Bar>.value(value: bar), 
    Provider<Baz>.value(value: baz), 
  ], 
  child: MyApp(...), 
)

MultiProvider ( 
  providers: [ 
    Provider<Foo> ( 
      builder: (context) => Foo(),
    ), 
    ProxyProvider<Foo, Bar>(
      builder: (context, value, previous) => Bar(value),
    ), 
  ], 
  child: MyApp(...),
)

Cara mendengarkan banyak penyedia sekaligus

Consumer2<MyModel, int>(
  builder: (context, value, value2, child) {
    //value  MyModel
    //value2  int
  },
);

Kesimpulan