Flutter Flitter riverpod小部件调用了两次

我正在努力学习颤振和Riverpod，并尝试使用干净的代码。我只是注意到我的小部件被调用了两次。如何避免不必要的操作

我的项目只是一个导航栏，根据我们单击的按钮加载视图

我的导航栏屏幕：

class NavigationBarScreen extends HookWidget
{

  @override
  Widget build(BuildContext context) {

    print('build navigationScreen');
    final _pageModel = useProvider(navigationProvider.state);

    return SafeArea(
      child: Scaffold(
        body : context.read(navigationProvider).buildScreen(_pageModel.pageState),
        bottomNavigationBar: Container(
              margin: EdgeInsets.only(left : 8, right : 8, bottom: 8),
              decoration: BoxDecoration(
                borderRadius: BorderRadius.only(
                    topRight: Radius.circular(20), topLeft: Radius.circular(20)),
                boxShadow: [
                  BoxShadow(color: AppColors.colorShadowLight, spreadRadius: 0, blurRadius: 10),
                ],
              ),
              child: ClipRRect(
                borderRadius: BorderRadius.circular(50.0),
                child: BottomNavigationBar(
                  type: BottomNavigationBarType.fixed,
                  backgroundColor: AppColors.colorBgDark,
                  fixedColor: AppColors.colorContrastOrange,
                  unselectedItemColor: AppColors.colorFontLight2,
                  currentIndex: _pageModel.navigationIndexItem,
                  showSelectedLabels: false,
                  showUnselectedLabels: false,
                  onTap: context.read(navigationProvider).selectPage,
                  items: [
                    BottomNavigationBarItem(
                      icon: Icon(Icons.home),
                      title: Text('Home'),
                    ),
                    BottomNavigationBarItem(
                      icon: Icon(Icons.settings),
                      title: Text('Settings'),
                    ),
                  ],
                ),
              ),
            ),
      ),
    );
  }

}

enum NavigationBarState
{
  HOME, PROFIL
}

class NavigationNotifier extends StateNotifier<NavigationBarModel>
{
  NavigationNotifier() : super(_initialPage);

  static const int _initialIndex = 0;
  static const NavigationBarState _initialState = NavigationBarState.HOME;
  static const _initialPage = NavigationBarModel(pageState : _initialState, navigationIndexItem : _initialIndex);

  void selectPage(int i)
  {
    switch (i)
    {
      case 0:
        state = NavigationBarModel(pageState : NavigationBarState.HOME, navigationIndexItem : i);
        break;
      case 1:
        state = NavigationBarModel(pageState : NavigationBarState.PROFIL, navigationIndexItem : i);
        break;
    }
  }

  Widget buildScreen(NavigationBarState page)
  {
    switch (page)
    {
      case NavigationBarState.HOME:
        return HomeScreen();
        break;
      case NavigationBarState.PROFIL:
        return Text("Page under construction");
        break;
    }
    return null;
  }

}

class NavigationBarModel {
  const NavigationBarModel({this.pageState, this.navigationIndexItem});
  final NavigationBarState pageState;
  final int navigationIndexItem;
}

I/flutter (32738): build navigationScreen
I/flutter (32738): build homeScreen
I/flutter (32738): build navigationScreen
I/flutter (32738): build homeScreen

我的导航通知程序：

class NavigationBarScreen extends HookWidget
{

  @override
  Widget build(BuildContext context) {

    print('build navigationScreen');
    final _pageModel = useProvider(navigationProvider.state);

    return SafeArea(
      child: Scaffold(
        body : context.read(navigationProvider).buildScreen(_pageModel.pageState),
        bottomNavigationBar: Container(
              margin: EdgeInsets.only(left : 8, right : 8, bottom: 8),
              decoration: BoxDecoration(
                borderRadius: BorderRadius.only(
                    topRight: Radius.circular(20), topLeft: Radius.circular(20)),
                boxShadow: [
                  BoxShadow(color: AppColors.colorShadowLight, spreadRadius: 0, blurRadius: 10),
                ],
              ),
              child: ClipRRect(
                borderRadius: BorderRadius.circular(50.0),
                child: BottomNavigationBar(
                  type: BottomNavigationBarType.fixed,
                  backgroundColor: AppColors.colorBgDark,
                  fixedColor: AppColors.colorContrastOrange,
                  unselectedItemColor: AppColors.colorFontLight2,
                  currentIndex: _pageModel.navigationIndexItem,
                  showSelectedLabels: false,
                  showUnselectedLabels: false,
                  onTap: context.read(navigationProvider).selectPage,
                  items: [
                    BottomNavigationBarItem(
                      icon: Icon(Icons.home),
                      title: Text('Home'),
                    ),
                    BottomNavigationBarItem(
                      icon: Icon(Icons.settings),
                      title: Text('Settings'),
                    ),
                  ],
                ),
              ),
            ),
      ),
    );
  }

}

enum NavigationBarState
{
  HOME, PROFIL
}

class NavigationNotifier extends StateNotifier<NavigationBarModel>
{
  NavigationNotifier() : super(_initialPage);

  static const int _initialIndex = 0;
  static const NavigationBarState _initialState = NavigationBarState.HOME;
  static const _initialPage = NavigationBarModel(pageState : _initialState, navigationIndexItem : _initialIndex);

  void selectPage(int i)
  {
    switch (i)
    {
      case 0:
        state = NavigationBarModel(pageState : NavigationBarState.HOME, navigationIndexItem : i);
        break;
      case 1:
        state = NavigationBarModel(pageState : NavigationBarState.PROFIL, navigationIndexItem : i);
        break;
    }
  }

  Widget buildScreen(NavigationBarState page)
  {
    switch (page)
    {
      case NavigationBarState.HOME:
        return HomeScreen();
        break;
      case NavigationBarState.PROFIL:
        return Text("Page under construction");
        break;
    }
    return null;
  }

}

class NavigationBarModel {
  const NavigationBarModel({this.pageState, this.navigationIndexItem});
  final NavigationBarState pageState;
  final int navigationIndexItem;
}

I/flutter (32738): build navigationScreen
I/flutter (32738): build homeScreen
I/flutter (32738): build navigationScreen
I/flutter (32738): build homeScreen

在run inspector中，我有以下内容：

class NavigationBarScreen extends HookWidget
{

  @override
  Widget build(BuildContext context) {

    print('build navigationScreen');
    final _pageModel = useProvider(navigationProvider.state);

    return SafeArea(
      child: Scaffold(
        body : context.read(navigationProvider).buildScreen(_pageModel.pageState),
        bottomNavigationBar: Container(
              margin: EdgeInsets.only(left : 8, right : 8, bottom: 8),
              decoration: BoxDecoration(
                borderRadius: BorderRadius.only(
                    topRight: Radius.circular(20), topLeft: Radius.circular(20)),
                boxShadow: [
                  BoxShadow(color: AppColors.colorShadowLight, spreadRadius: 0, blurRadius: 10),
                ],
              ),
              child: ClipRRect(
                borderRadius: BorderRadius.circular(50.0),
                child: BottomNavigationBar(
                  type: BottomNavigationBarType.fixed,
                  backgroundColor: AppColors.colorBgDark,
                  fixedColor: AppColors.colorContrastOrange,
                  unselectedItemColor: AppColors.colorFontLight2,
                  currentIndex: _pageModel.navigationIndexItem,
                  showSelectedLabels: false,
                  showUnselectedLabels: false,
                  onTap: context.read(navigationProvider).selectPage,
                  items: [
                    BottomNavigationBarItem(
                      icon: Icon(Icons.home),
                      title: Text('Home'),
                    ),
                    BottomNavigationBarItem(
                      icon: Icon(Icons.settings),
                      title: Text('Settings'),
                    ),
                  ],
                ),
              ),
            ),
      ),
    );
  }

}

enum NavigationBarState
{
  HOME, PROFIL
}

class NavigationNotifier extends StateNotifier<NavigationBarModel>
{
  NavigationNotifier() : super(_initialPage);

  static const int _initialIndex = 0;
  static const NavigationBarState _initialState = NavigationBarState.HOME;
  static const _initialPage = NavigationBarModel(pageState : _initialState, navigationIndexItem : _initialIndex);

  void selectPage(int i)
  {
    switch (i)
    {
      case 0:
        state = NavigationBarModel(pageState : NavigationBarState.HOME, navigationIndexItem : i);
        break;
      case 1:
        state = NavigationBarModel(pageState : NavigationBarState.PROFIL, navigationIndexItem : i);
        break;
    }
  }

  Widget buildScreen(NavigationBarState page)
  {
    switch (page)
    {
      case NavigationBarState.HOME:
        return HomeScreen();
        break;
      case NavigationBarState.PROFIL:
        return Text("Page under construction");
        break;
    }
    return null;
  }

}

class NavigationBarModel {
  const NavigationBarModel({this.pageState, this.navigationIndexItem});
  final NavigationBarState pageState;
  final int navigationIndexItem;
}

I/flutter (32738): build navigationScreen
I/flutter (32738): build homeScreen
I/flutter (32738): build navigationScreen
I/flutter (32738): build homeScreen

编辑：在我的导航栏屏幕中，我更改了以下内容：

body : context.read(navigationProvider).buildScreen(_pageModel.pageState),

据此：

body : useProvider(navigationProvider).buildScreen(_pageModel.pageState),

---

context.read（）必须在onPressed、onTap、。。。但是我得到了相同的结果，我的navigationBarScreen被调用了两次…

我无法运行您的代码，因为缺少部分，但我最好的猜测是，因为您正在查看提供程序本身和提供程序状态，所以它被调用了两次

@覆盖
小部件构建（构建上下文）{
打印（“构建导航屏幕”）；
//这是你正在收听的国家广播
final _pageModel=useProvider（navigationProvider.state）；
返回安全区(
孩子：脚手架(
//这里您正在收听提供商的节目
正文：context.read（navigationProvider）.buildScreen（_pageModel.pageState），

我建议重构StateNotifier，而不是从navigationProvider状态获取页面模型并将其传递回navigationProvider

class NavigationNotifier扩展了StateNotifier
{
NavigationNotifier（）：超级（\u initialPage）；
静态常数int _initialIndex=0；
静态常量NavigationBarState _initialState=NavigationBarState.HOME；
静态常量_initialPage=NavigationBarModel（页面状态：_initialState，navigationIndexItem:_initialIndex）；
无效选择页（int i）
{
开关（一）
{
案例0：
状态=NavigationBarModel（页面状态：NavigationBarState.HOME，navigationIndexItem:i）；
打破
案例1：
状态=NavigationBarModel（页面状态：NavigationBarState.profile，navigationIndexItem:i）；
打破
}
}
Widget buildScreen（）
{
开关（state.pageState）
{
案例导航BarState.HOME：
返回主屏幕（）；
打破
案例导航BarState.profile：
返回文本（“正在构建的页面”）；
打破
}
返回null；
}
}

---

然后从构建方法的顶部删除

final\u pageModel=useProvider（navigationProvider.state）；

。

感谢您的回复。