set_state 2.1.1

A subclass of the State object placed in a static collection.

example/lib/main.dart

import 'package:flutter/material.dart';

import 'package:set_state/set_state.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  //
  MyApp({Key key}) : super(key: key);
  @override
  _MyAppState createState() => _MyAppState();
}

/// Demonstrates how to explicitly 're-create' a State object
class _MyAppState extends SetState<MyApp> {
  /// Key identifies the widget. New key? New widget!
  Key _homeKey = UniqueKey();

  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) => MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(key: _homeKey),
      );

  void setState(VoidCallback fn) {
    _homeKey = UniqueKey();
    super.setState(fn);
  }
}

class MyHomePage extends StatefulWidget {
  //
  MyHomePage({Key key}) : super(key: key);
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

/// The home page for this app.
class _MyHomePageState extends SetState<MyHomePage> {
  //
  _MyHomePageState() : super() {
    bloc = _HomePageBloc<_MyHomePageState>();
  }
  _HomePageBloc bloc;

  /// Supply a means to access its bloc
  void onPressed() => bloc.onPressed();

  @override
  void dispose() {
    // You should clean up after yourself.
    bloc.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(
          title: const Text('Home Page'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              const Text(
                'You have pushed the button this many times:',
              ),
              Text(
                '${bloc.data}',
                style: Theme.of(context).textTheme.headline4,
              ),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: onPressed,
          child: Icon(Icons.add),
        ),
        persistentFooterButtons: <Widget>[
          RaisedButton(
            child: const Text(
              'Second Page',
            ),
            onPressed: () {
              Navigator.push(
                  context,
                  MaterialPageRoute(
                      builder: (BuildContext context) => _SecondPage()));
            },
          ),
        ],
      );
}

/// The second page displayed in this app.
class _SecondPage extends StatefulWidget {
  //
  _SecondPage({Key key}) : super(key: key);

  @override
  State createState() => _SecondPageState();
}

class _SecondPageState extends SetState<_SecondPage> {
  // constructor
  _SecondPageState()
      : homeState = SetState.of<_MyHomePageState>(),
        super() {
    bloc = _SecondPageBloc();
  }
  _SecondPageBloc bloc;
  _MyHomePageState homeState;

  @override
  void dispose() {
    // You should clean up after yourself.
    bloc.dispose();
    homeState = null;
    super.dispose();
  }

  // Supply a means to access its bloc
  void onPressed() => bloc.onPressed();

  @override
  Widget build(BuildContext context) => Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              const Text("You're on the Second Page"),
              const Text('You have pushed the button this many times:'),
              Text(
                '${bloc.data}',
                style: Theme.of(context).textTheme.headline4,
              ),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: bloc.onPressed,
          child: Icon(Icons.add),
        ),
        persistentFooterButtons: <Widget>[
          RaisedButton(
            child: const Text('Home Page Counter'),
            onPressed: homeState?.onPressed,
          ),
          RaisedButton(
            child: const Text(
              'Home Page',
            ),
            onPressed: () {
              Navigator.pop(context);
            },
          ),
          RaisedButton(
            child: const Text(
              'Third Page',
            ),
            onPressed: () {
              Navigator.push(
                  context,
                  MaterialPageRoute(
                      builder: (BuildContext context) => _ThirdPage()));
            },
          ),
        ],
      );
}

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

  @override
  _ThirdPageState createState() => _ThirdPageState();
}

/// Demonstrates accessing the 'first' SetState object.
class _ThirdPageState extends SetState<_ThirdPage> {
  _ThirdPageState()
      : secondState = SetState.of<_SecondPageState>(),
        super() {
    // The corresponding Bloc
    bloc = _ThirdPageBloc();
    // Retrieve a specified State object.
    homeState = SetState.of<_MyHomePageState>();
    // Retrieve the very 'first' State object!
    appState = SetState.root;
  }
  _SecondPageState secondState;
  _ThirdPageBloc bloc;
  _MyHomePageState homeState;
  SetState appState;

  @override
  void dispose() {
    // You should clean up after yourself.
    secondState = null;
    homeState = null;
    super.dispose();
  }

  // Supply a means to externally access this State objects functionality.
  void onPressed() => bloc.onPressed();

  @override
  Widget build(BuildContext context) => Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              const Text("You're on the Third page."),
              const Text('You have pushed the button this many times:'),
              Text(
                '${bloc.data}',
                style: Theme.of(context).textTheme.headline4,
              ),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: onPressed,
          child: Icon(Icons.add),
        ),
        persistentFooterButtons: <Widget>[
          RaisedButton(
            child: const Text('Home Page Counter'),
            onPressed: homeState?.onPressed,
          ),
          RaisedButton(
            child: const Text('Second Page Counter'),
            onPressed: secondState?.onPressed,
          ),
          RaisedButton(
            child: const Text('Home Page New Key'),
            onPressed: () {
              appState?.setState(() {});
            },
          ),
          RaisedButton(
            child: const Text('Home Page'),
            onPressed: () {
              Navigator.popUntil(context, ModalRoute.withName('/'));
            },
          ),
          RaisedButton(
            child: const Text('Second Page'),
            onPressed: () {
              Navigator.pop(context);
            },
          ),
        ],
      );
}

/// Explicit specify the type of State object to work with.
class _HomePageBloc<T extends SetState> extends _CounterBloc {
  // 1)
  _HomePageBloc() {
    state = SetState.of<T>();
  }

// // 2)
// _HomePageBloc() : super() {
//   state = SetState.of<_HomePageBloc>();
// }

//  // 3 )
// factory _HomePageBloc() {
//   _this ??= _HomePageBloc._();
//   // Assign the 'new' State object.
//   _this.state = SetState.of<T>();
//   return _this;
// }
// _HomePageBloc._();
// static _HomePageBloc _this;

//  // 4)
// /// POWERFUL: You can override the instance field with a getter.
// /// As a getter, you don't have to instantiate until needed (and available).
// @override
//  SetState get state {
//   if(_state == null){
//      _state ??= SetState.of<T>();
//   }
//   return _state;
//   }
// SetState _state;
}

//class _SecondPageBloc<T extends SetState> extends _CounterBloc {
class _SecondPageBloc extends _CounterBloc {
  // // 1)
  // _SecondPageBloc() {
  //   state = SetState.of<T>();
  // }

  // // 2)
  // _SecondPageBloc() {
  //   state = SetState.of<_SecondPageState>();
  // }

  // 3 )
  // Retain the count even after its State is disposed!
  factory _SecondPageBloc() {
    _this ??= _SecondPageBloc._();
    // Assign the 'new' State object.
    _this.state = SetState.of<_SecondPageState>();
    return _this;
  }
  _SecondPageBloc._();
  static _SecondPageBloc _this;

//  // 4)
// /// POWERFUL: You can override the instance field with a getter.
// /// As a getter, you don't have to instantiate until needed (and available).
// @override
//  SetState get state => _state ??= SetState.of<T>();
// SetState _state;
}

/// Retain a State object by knowing the type you're looking for.
class _ThirdPageBloc extends _CounterBloc {
  // // 1)
  // _ThirdPageBloc() {
  //   state = SetState.of<T>();
  // }

  // // 2)
  // _ThirdPageBloc() {
  //   state = SetState.of<_ThirdPageBloc>();
  // }

  //  // 3 )
  // factory _ThirdPageBloc() {
  //   _this ??= _ThirdPageBloc._();
  //   // Assign the 'new' State object.
  //   _this.state = SetState.of<_ThirdPageState>();
  //   return _this;
  // }
  // _ThirdPageBloc._();
  // static _ThirdPageBloc _this;

  // 4)
  /// POWERFUL: You can override the field with a getter.
  /// As a getter, you don't have to instantiate until needed (and available).
  @override
  SetState get state => _state ??= SetState.of<_ThirdPageState>();
  SetState _state;
}

/// Made abstract to 'remind the developer' to supply a SetState object.
abstract class _CounterBloc with StateBloc {
  /// The 'data' is a lone integer.
  int _counter = 0;

  /// Getter to safely access the data.
  int get data => _counter;

  /// The generic function (Flutter API) called to manipulate the data.
  void onPressed() => setState(() {
        _counter++;
      });
}