Flutter状态管理插件flutter_typed_redux的使用

Flutter状态管理插件flutter_typed_redux的使用

在Flutter应用开发过程中，状态管理是一个非常重要的部分。flutter_typed_redux 是一个基于Redux的状态管理库，它提供了类型安全的功能来简化Redux Store的使用。

简介

flutter_typed_redux 提供了一组工具，可以方便地将类型化的Redux Store与Flutter小部件集成在一起。该库借鉴了 flutter_redux 的灵感，为Redux状态管理提供了一种更简洁的方式。

示例代码

以下是一个简单的示例，演示如何使用 flutter_typed_redux 来构建一个Flutter应用。

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

// 定义状态
class CounterState {
  final int count;

  CounterState({required this.count});
}

// 定义动作
abstract class CounterAction {}

class Increment extends CounterAction {}

class Decrement extends CounterAction {}

// 定义reducer
CounterState counterReducer(CounterState state, dynamic action) {
  if (action is Increment) {
    return CounterState(count: state.count + 1);
  } else if (action is Decrement) {
    return CounterState(count: state.count - 1);
  }
  return state;
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StoreProvider<CounterState>(
      store: Store<CounterState>(counterReducer, initialState: CounterState(count: 0)),
      child: MaterialApp(
        title: 'Flutter Typed Redux Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(),
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StoreConnector<CounterState, _ViewModel>(
      converter: (store) => _ViewModel.fromStore(store),
      builder: (context, vm) {
        return Scaffold(
          appBar: AppBar(
            title: Text('Flutter Typed Redux Demo'),
          ),
          body: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(
                  'You have pushed the button this many times:',
                ),
                Text(
                  '${vm.state.count}',
                  style: Theme.of(context).textTheme.headline4,
                ),
              ],
            ),
          ),
          floatingActionButton: Row(
            mainAxisAlignment: MainAxisAlignment.end,
            children: [
              FloatingActionButton(
                onPressed: () => vm.dispatch(Increment()),
                tooltip: 'Increment',
                child: Icon(Icons.add),
              ),
              SizedBox(width: 10),
              FloatingActionButton(
                onPressed: () => vm.dispatch(Decrement()),
                tooltip: 'Decrement',
                child: Icon(Icons.remove),
              ),
            ],
          ),
        );
      },
    );
  }
}

class _ViewModel {
  final CounterState state;

  _ViewModel(this.state);

  static _ViewModel fromStore(Store<CounterState> store) {
    return _ViewModel(store.state);
  }

  void dispatch(CounterAction action) {
    store.dispatch(action);
  }
}

代码解释

1. 定义状态:

   class CounterState {
     final int count;
   
     CounterState({required this.count});
   }
   

   这里我们定义了一个简单的状态类 CounterState，其中包含一个整数属性 count。

2. 定义动作:

   abstract class CounterAction {}
   
   class Increment extends CounterAction {}
   
   class Decrement extends CounterAction {}
   

   我们定义了一个抽象类 CounterAction 和两个具体的动作类 Increment 和 Decrement。

3. 定义reducer:

   CounterState counterReducer(CounterState state, dynamic action) {
     if (action is Increment) {
       return CounterState(count: state.count + 1);
     } else if (action is Decrement) {
       return CounterState(count: state.count - 1);
     }
     return state;
   }
   

   我们定义了一个reducer函数 counterReducer，根据不同的动作更新状态。

4. 创建应用:

   void main() {
     runApp(MyApp());
   }
   
   class MyApp extends StatelessWidget {
     @override
     Widget build(BuildContext context) {
       return StoreProvider<CounterState>(
         store: Store<CounterState>(counterReducer, initialState: CounterState(count: 0)),
         child: MaterialApp(
           title: 'Flutter Typed Redux Demo',
           theme: ThemeData(
             primarySwatch: Colors.blue,
           ),
           home: MyHomePage(),
         ),
       );
     }
   }
   

   在主函数中，我们使用 StoreProvider 将 Store 提供给整个应用，并设置初始状态。

5. 创建主页:

   class MyHomePage extends StatelessWidget {
     @override
     Widget build(BuildContext context) {
       return StoreConnector<CounterState, _ViewModel>(
         converter: (store) => _ViewModel.fromStore(store),
         builder: (context, vm) {
           return Scaffold(
             appBar: AppBar(
               title: Text('Flutter Typed Redux Demo'),
             ),
             body: Center(
               child: Column(
                 mainAxisAlignment: MainAxisAlignment.center,
                 children: <Widget>[
                   Text(
                     'You have pushed the button this many times:',
                   ),
                   Text(
                     '${vm.state.count}',
                     style: Theme.of(context).textTheme.headline4,
                   ),
                 ],
               ),
             ),
             floatingActionButton: Row(
               mainAxisAlignment: MainAxisAlignment.end,
               children: [
                 FloatingActionButton(
                   onPressed: () => vm.dispatch(Increment()),
                   tooltip: 'Increment',
                   child: Icon(Icons.add),
                 ),
                 SizedBox(width: 10),
                 FloatingActionButton(
                   onPressed: () => vm.dispatch(Decrement()),
                   tooltip: 'Decrement',
                   child: Icon(Icons.remove),
                 ),
               ],
             ),
           );
         },
       );
     }
   }
   

   在主页中，我们使用 StoreConnector 将状态和操作传递给视图模型 _ViewModel，并构建UI。

6. 创建视图模型:

   class _ViewModel {
     final CounterState state;
   
     _ViewModel(this.state);
   
     static _ViewModel fromStore(Store<CounterState> store) {
       return _ViewModel(store.state);
     }
   
     void dispatch(CounterAction action) {
       store.dispatch(action);
     }
   }