Question

通过使用RiverPod状态管理，我尝试进行自我改进，以学习和使用该状态我做了一个简单的项目，并且试图通过按图标打开Drawer在AppBar（位于另一个类和文件中）中，不幸的是，与RiverPod示例代码一样，我的代码无法正常工作，并且主类也不会在单击图标时触发

我只是想通过单击AppBar上的图标来打开抽屉

主文件：

void main() {
  runApp(ProviderScope(child: MyApp()));
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Riverpod Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  @override
  Widget build(BuildContext context) {
    final drawerState = StateNotifierProvider<DrawerVisibility>((_)=>DrawerVisibility());
    return Consumer(
      builder: (context, read, _) {
        final state = read(drawerState.state);
        print('CLICKED $state');
        if(state){
          _scaffoldKey.currentState.openDrawer();
        }
        return Scaffold(
          key: _scaffoldKey,
          appBar: MyAppBar(),
          drawer: Drawer(),
          body: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(
                  'You have pushed the button this many times:',
                ),
              ],
            ),
          ),
        );
      },
    );
  }
}

AppBar类文件内容：

class MyAppBar extends StatelessWidget with PreferredSizeWidget {
  @override
  Widget build(BuildContext context) {
    final drawerState = StateNotifierProvider<DrawerVisibility>((_)=>DrawerVisibility());
    return AppBar(
      automaticallyImplyLeading: false,
      title: Row(
        mainAxisAlignment: MainAxisAlignment.start,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: <Widget>[
          IconButton(icon: Icon(Icons.menu), onPressed: () {
            context.read(drawerState).changeDrawerState();
          }),
          Text('My Sample'),
        ],
      ),
    );
  }

  @override
  Size get preferredSize => Size.fromHeight(kToolbarHeight);
}

最后是RiverPod类

class DrawerVisibility extends StateNotifier {
  DrawerVisibility() : super(false);

  void changeDrawerState() => state = true;
}

另一个问题是我第一次启动应用程序时得到以下输出：

I/flutter (12240): CLICKED false
I/flutter (12240): CLICKED false

无需单击任何图标

Answer 1

您应该尝试使用Consumer而不是ProviderListener，当您要显示对话框，小吃店，推/弹出或在这种情况下打开抽屉时，它会更好。最后，与其在每个构建方法中创建最终的提供程序，不如将其作为最终的全局参数创建一次，因此在您阅读/观看的每个小部件中，它都使用相同的实例

/// Create a final global StateNotifierProvider in your file instead of one inside each widget
final drawerState = StateNotifierProvider<DrawerVisibility>((_)=>DrawerVisibility());

class _MyHomePageState extends State<MyHomePage> {
  GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  @override
  Widget build(BuildContext context) {
    return ProviderListener<bool>(
      onChange: (context, state) {
        if(state) _scaffoldKey.currentState.openDrawer();
        //maybe check if the _scaffoldKey is mounted or is the drawer open before doing something
      },
      provider: drawerState.state,
      child: Scaffold(
        key: _scaffoldKey,
        appBar: MyAppBar(),
        drawer: Drawer(),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
            ],
          ),
        ),
      ),
    );
  }
}

然后在MyAppBar中删除抽屉状态，以便它使用与HomePage相同的全局变量，并且在关闭抽屉时，还应再次将状态设置为false

使用RiverPod状态管理的颤振变化抽屉状态

1 个答案: