redux主要由??Store???、??Action???、??Reducer??三部分组成

• ??Store???用于存储和管理??State??
• ??Action??用于用户触发的一种行为
• ??Reducer???用于根据Action产生新的??State??
  flutter redux流程1.??Widget???通过??StoreConnector???绑定??Store???中的??State??数据
  2.??Widget???通过??Action??触发一种新的行为
  3.??Reducer???根据收到的??Action???更新??State??
  4.更新??Store???中的??State???绑定的??Widget??
  根据以上流程，我们实现项目中的主题切换功能。
  项目集成flutter redux库集成flutter redux修改项目根目录下??pubspec.yaml??，并添加依赖
  

  flutter_redux: ^0.5.3 ?

  
  初始化Store首先看下??Store??的构造函数，如下面代码所示
  

  Store( this.reducer, { State initialState, List middleware = const [], bool syncStream: false, bool distinct: false, }) : _changeController = new StreamController.broadcast(sync: syncStream) { _state = initialState; _dispatchers = _createDispatchers( middleware, _createReduceAndNotify(distinct), ); }

  
  根据上面的构造函数，我们首先需要创建??State???，并且还需要完成??State???初始化；然后需要创建??Reducer???；最后需要创建??Middleware??（暂不是本文需要讲解的内容）；
  

创建State
创建一个??State???对象??AppState???,用于储存需要共享的主题数据，并且完成??AppState??初始化工作，如下面代码所示

class AppState { ThemeData themeData; AppState({this.themeData}); factory AppState.initial() => AppState(themeData: AppTheme.theme); }

AppTheme???类中定义了一个默认主题??theme??，如下面代码所示

class AppTheme { static final ThemeData _themeData = https://www.it610.com/article/new ThemeData.light(); static get theme { return _themeData.copyWith( primaryColor: Colors.black, ); } }

到此，完成了State的相关操作。
创建Reducer
创建一个??Reducer???方法??appReducer???,为??AppState???类里的每一个参数创建一个??Reducer??，如下面代码所示

AppState appReducer(AppState state, action) { return AppState( themeData: themeReducer(state.themeData, action), ); }

而??themeReducer??将ThemeData和所有跟切换主题的行为绑定在一起,如下面代码所示

final themeReducer = combineReducers([ TypedReducer(_refresh), ]); ThemeData _refresh(ThemeData themeData, action) { themeData = https://www.it610.com/article/action.themeData; return themeData; }

通过??flutter redux???的??combineReducers???与??TypedReducer???将??RefreshThemeDataAction???和??_refresh???绑定在一起，当用户每次发出??RefreshThemeDataAction???时，都会触发??_refresh???,用来更新??themeData??。
创建Action
创建一个??Action???对象??RefreshThemeDataAction??,如下面代码所示

class RefreshThemeDataAction{ final ThemeData themeData; RefreshThemeDataAction(this.themeData); }

??RefreshThemeDataAction??的参数themeData是用来接收新切换的主题。
代码集成
创建??Store???所有的准备工作都已准备，下面创建??Store??，如下面代码所示

final store = new Store( appReducer, initialState: AppState.initial(), );

然后用??StoreProvider???加载store,??MaterialApp???通过??StoreConnector???与??Store???保持连接。到此我们已经完成了??flutter redux??的初始化工作，如下面代码所示

void main() { final store = new Store( appReducer, initialState: AppState.initial(), ); runApp(OpenGitApp(store)); }class OpenGitApp extends StatelessWidget { final Store store; OpenGitApp(this.store); @override Widget build(BuildContext context) { return new StoreProvider( store: store, child: StoreConnector( converter: _ViewModel.fromStore, builder: (context, vm) { return new MaterialApp( theme: vm.themeData, routes: AppRoutes.getRoutes(), ); }, ), ); } }

【Flutter主题切换 flutter redux】?StoreConnector???通过??converter???在??_ViewModel???中转化??store.state???的数据，最后通过??builder???返回实际需要更新主题的控件，这样就完成了数据和控件的绑定。??_ViewModel??的代码如下面所示

class _ViewModel { final ThemeData themeData; _ViewModel({this.themeData}); static _ViewModel fromStore(Store store) { return _ViewModel( themeData: store.state.themeData, ); } }

用户行为
最后，只需要添加切换主题部分的代码即可，这部分代码是从官方??gallery?? demo里的Style/Colors copy出来的，不做过多分析，如下面代码所示

const double kColorItemHeight = 48.0; class Palette { Palette({this.name, this.primary, this.accent, this.threshold = 900}); final String name; final MaterialColor primary; final MaterialAccentColor accent; final int threshold; // titles for indices > threshold are white, otherwise blackbool get isValid => name != null && primary != null && threshold != null; }final List allPalettes = [ new Palette( name: 'RED', primary: Colors.red, accent: Colors.redAccent, threshold: 300), new Palette( name: 'PINK', primary: Colors.pink, accent: Colors.pinkAccent, threshold: 200), new Palette( name: 'PURPLE', primary: Colors.purple, accent: Colors.purpleAccent, threshold: 200), new Palette( name: 'DEEP PURPLE', primary: Colors.deepPurple, accent: Colors.deepPurpleAccent, threshold: 200), new Palette( name: 'INDIGO', primary: Colors.indigo, accent: Colors.indigoAccent, threshold: 200), new Palette( name: 'BLUE', primary: Colors.blue, accent: Colors.blueAccent, threshold: 400), new Palette( name: 'LIGHT BLUE', primary: Colors.lightBlue, accent: Colors.lightBlueAccent, threshold: 500), new Palette( name: 'CYAN', primary: Colors.cyan, accent: Colors.cyanAccent, threshold: 600), new Palette( name: 'TEAL', primary: Colors.teal, accent: Colors.tealAccent, threshold: 400), new Palette( name: 'GREEN', primary: Colors.green, accent: Colors.greenAccent, threshold: 500), new Palette( name: 'LIGHT GREEN', primary: Colors.lightGreen, accent: Colors.lightGreenAccent, threshold: 600), new Palette( name: 'LIME', primary: Colors.lime, accent: Colors.limeAccent, threshold: 800), new Palette( name: 'YELLOW', primary: Colors.yellow, accent: Colors.yellowAccent), new Palette(name: 'AMBER', primary: Colors.amber, accent: Colors.amberAccent), new Palette( name: 'ORANGE', primary: Colors.orange, accent: Colors.orangeAccent, threshold: 700), new Palette( name: 'DEEP ORANGE', primary: Colors.deepOrange, accent: Colors.deepOrangeAccent, threshold: 400), new Palette(name: 'BROWN', primary: Colors.brown, threshold: 200), new Palette(name: 'GREY', primary: Colors.grey, threshold: 500), new Palette(name: 'BLUE GREY', primary: Colors.blueGrey, threshold: 500), ]; class ColorItem extends StatelessWidget { const ColorItem( {Key key, @required this.index, @required this.color, this.prefix = '', this.onChangeTheme}) : assert(index != null), assert(color != null), assert(prefix != null), super(key: key); final int index; final Color color; final String prefix; final Function(Color) onChangeTheme; String colorString() => "#${color.value.toRadixString(16).padLeft(8, '0').toUpperCase()}"; @override Widget build(BuildContext context) { return new Semantics( container: true, child: new Container( height: kColorItemHeight, padding: const EdgeInsets.symmetric(horizontal: 16.0), color: color, child: new SafeArea( top: false, bottom: false, child: FlatButton( child: new Row( mainAxisAlignment: MainAxisAlignment.spaceBetween, crossAxisAlignment: CrossAxisAlignment.center, children: [ new Text('$prefix$index'), new Text(colorString()), ], ), onPressed: () { onChangeTheme(color); }, ), ), ), ); } }class PaletteTabView extends StatelessWidget { static const List primaryKeys = const [ 50, 100, 200, 300, 400, 500, 600, 700, 800, 900 ]; static const List accentKeys = const [100, 200, 400, 700]; PaletteTabView({Key key, @required this.colors, this.onChangeTheme}) : assert(colors != null && colors.isValid), super(key: key); final Palette colors; final Function(Color) onChangeTheme; @override Widget build(BuildContext context) { final TextTheme textTheme = Theme.of(context).textTheme; final TextStyle whiteTextStyle = textTheme.body1.copyWith(color: Colors.white); final TextStyle blackTextStyle = textTheme.body1.copyWith(color: Colors.black); final List colorItems = primaryKeys.map((int index) { return new DefaultTextStyle( style: index > colors.threshold ? whiteTextStyle : blackTextStyle, child: new ColorItem( index: index, color: colors.primary[index], onChangeTheme: onChangeTheme), ); }).toList(); if (colors.accent != null) { colorItems.addAll(accentKeys.map((int index) { return new DefaultTextStyle( style: index > colors.threshold ? whiteTextStyle : blackTextStyle, child: new ColorItem( index: index, color: colors.accent[index], prefix: 'A', onChangeTheme: onChangeTheme), ); }).toList()); }return new ListView( itemExtent: kColorItemHeight, children: colorItems, ); } }class ThemeSelectPage extends StatelessWidget { @override Widget build(BuildContext context) { return StoreConnector( converter: _ViewModel.fromStore, builder: (context, vm) { return new DefaultTabController( length: allPalettes.length, child: new Scaffold( appBar: new AppBar( elevation: 0.0, title: const Text("主题色"), bottom: new TabBar( isScrollable: true, tabs: allPalettes .map((Palette swatch) => new Tab(text: swatch.name)) .toList(), ), ), body: new TabBarView( children: allPalettes.map((Palette colors) { return new PaletteTabView( colors: colors, onChangeTheme: vm.onChangeTheme, ); }).toList(), ), ), ); }); } }class _ViewModel { final Function(Color) onChangeTheme; _ViewModel({this.onChangeTheme}); static _ViewModel fromStore(Store store) { return _ViewModel( onChangeTheme: (color) { SharedPrfUtils.saveInt(SharedPrfKey.SP_KEY_THEME_COLOR, color.value); store.dispatch(RefreshThemeDataAction(AppTheme.changeTheme(color))); }, ); } }

运行效果
执行代码，效果如下

文章图片

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