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Flutter 颤振：我应该如何使用继承的小部件？

flutter

Flutter 颤振：我应该如何使用继承的小部件？,flutter,state-management,inherited-widget,Flutter,State Management,Inherited Widget,简介：我认为原则上这个问题可能是共同的，但我觉得这个特定的应用程序不是。我谦恭地将其提交考虑，因此请温柔。我的代码在这里跌入了一个明显的陷阱，我根本不知道如何修复它。考虑了几个小时后，我甚至不知道该怎么办 问题：继承的小部件未更新其上方小部件中的状态 期望值：我希望当我在主页的页面视图上滑动时，底部AppBar的文本会更新。然而，这并没有发生 说明：我正在尝试使用InheritedWidget（InheritedPageIndex），我通过提供程序方法在根小部件（MaterialApp）上方初始

简介：我认为原则上这个问题可能是共同的，但我觉得这个特定的应用程序不是。我谦恭地将其提交考虑，因此请温柔。我的代码在这里跌入了一个明显的陷阱，我根本不知道如何修复它。考虑了几个小时后，我甚至不知道该怎么办

问题：继承的小部件未更新其上方小部件中的状态

期望值：我希望当我在主页的页面视图上滑动时，底部AppBar的文本会更新。然而，这并没有发生

说明：我正在尝试使用InheritedWidget（InheritedPageIndex），我通过提供程序方法在根小部件（MaterialApp）上方初始化了它（请参见下面的代码）。其中，有一个值向下传递到小部件树中它下面的小部件（MenuPage）。我希望此值在状态更改时更新；我试图通过在小部件树中的小部件下方滑动页面视图（主页）来修改它

代码：我重新编写并简化了我的代码，以便我们能够更轻松地诊断和修复问题，它看起来如下：

页面索引\u模型.省道

import 'package:flutter/material.dart';

    class PageIndex {
      PageIndex({@required this.index});
      double index = 0;
    }

import 'package:flutter/cupertino.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';

class InheritedPageIndex extends InheritedWidget {
  InheritedPageIndex({Key key, @required this.indexData, Widget child})
      : super(key: key, child: child);

  final PageIndex indexData;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => true;

  static PageIndex of(BuildContext context) => context
      .dependOnInheritedWidgetOfExactType<InheritedPageIndex>()
      .indexData;
}

import 'package:flutter/material.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';
import 'package:testinginheritedwidget/pages/menu_page.dart';
import 'package:testinginheritedwidget/providers/page_index_provider.dart';

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

    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return InheritedPageIndex(
          indexData: PageIndex(index: 0),
          child: MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Testing Inherited Widgets',
            home: MenuPage(),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/pages/home_page.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class MenuPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        return DefaultTabController(
          length: 3,
          child: Scaffold(
            //TODO: dot indicator
            resizeToAvoidBottomInset: false,
            appBar: AppBar(
              backgroundColor: Colors.black,
              title: Center(
                child: Text('Testing Inherited Widgets',
                    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
              ),
              bottom: TabBar(
                onTap: (tabIndex) {},
                labelColor: Colors.white,
                indicatorColor: Colors.white,
                tabs: const <Widget>[
                  Tab(icon: Icon(Icons.flight), child: Text('Flight')),
                  Tab(icon: Icon(Icons.map), child: Text('Map')),
                  Tab(icon: Icon(Icons.print), child: Text('Print')),
                ],
              ),
            ),
            body: SafeArea(
              child: TabBarView(
                children: <Widget>[
                  HomePage(),
                  HomePage(),
                  HomePage(),
                ],
              ),
            ),
            bottomNavigationBar: BottomAppBar(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
// *** PROBLEM 1 IS HERE ***
                  Text('${_pageIndex.index}'),
                ],
              ),
            ),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class HomePage extends StatefulWidget {
      @override
      _HomePageState createState() => _HomePageState();
    }

    class _HomePageState extends State<HomePage> {
      List<Widget> cards = [];

      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        for (var index = 0; index < 7; index++) {
          cards.add(
            Center(
              child: Text(
                '$index',
                style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
              ),
            ),
          );
          print(index);
        }
        return PageView(
          onPageChanged: (index) {
            setState(() {
//*** PROBLEM 2 IS HERE ***
              _pageIndex.index = index.toDouble();
              print('page index: ${_pageIndex.index}');
            });
          },
          children: cards,
        );
      }
    }

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/page_menu.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Testing Inherited Widgets',
      home: ChangeNotifierProvider(
        create: (BuildContext context) => Counter(0),
        child: MenuPage(),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int _counter;

  Counter(this._counter);

  getCounter() => _counter;

  setCounter(int counter) => _counter = counter;

  void increment(int counter) {
    _counter = counter;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/home_page.dart';

class MenuPage extends StatefulWidget {
  @override
  _MenuPageState createState() => _MenuPageState();
}

class _MenuPageState extends State<MenuPage> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return DefaultTabController(
      length: 3,
      child: Scaffold(
        //TODO: dot indicator
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Center(
            child: Text('Testing Inherited Widgets',
                style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
          ),
          bottom: TabBar(
            onTap: (tabIndex) {
              counter.increment(0);
            },
            labelColor: Colors.white,
            indicatorColor: Colors.white,
            tabs: const <Widget>[
              Tab(icon: Icon(Icons.flight), child: Text('Flight')),
              Tab(icon: Icon(Icons.map), child: Text('Map')),
              Tab(icon: Icon(Icons.print), child: Text('Print')),
            ],
          ),
        ),
        body: SafeArea(
          child: TabBarView(
            children: <Widget>[
              HomePage(),
              HomePage(),
              HomePage(),
            ],
          ),
        ),
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              //TODO: insert value below.
              Text(counter.getCounter().toString()),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> cards = [];

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    for (var index = 0; index < 7; index++) {
      cards.add(
        Center(
          child: Text(
            '$index',
            style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
          ),
        ),
      );
      print(index);
    }
    return PageView(
      onPageChanged: (index) {
        setState(() {
          counter.increment(index);
        });
      },
      children: cards,
    );
  }
}
页面索引提供程序。dart

import 'package:flutter/material.dart';

    class PageIndex {
      PageIndex({@required this.index});
      double index = 0;
    }

import 'package:flutter/cupertino.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';

class InheritedPageIndex extends InheritedWidget {
  InheritedPageIndex({Key key, @required this.indexData, Widget child})
      : super(key: key, child: child);

  final PageIndex indexData;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => true;

  static PageIndex of(BuildContext context) => context
      .dependOnInheritedWidgetOfExactType<InheritedPageIndex>()
      .indexData;
}

import 'package:flutter/material.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';
import 'package:testinginheritedwidget/pages/menu_page.dart';
import 'package:testinginheritedwidget/providers/page_index_provider.dart';

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

    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return InheritedPageIndex(
          indexData: PageIndex(index: 0),
          child: MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Testing Inherited Widgets',
            home: MenuPage(),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/pages/home_page.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class MenuPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        return DefaultTabController(
          length: 3,
          child: Scaffold(
            //TODO: dot indicator
            resizeToAvoidBottomInset: false,
            appBar: AppBar(
              backgroundColor: Colors.black,
              title: Center(
                child: Text('Testing Inherited Widgets',
                    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
              ),
              bottom: TabBar(
                onTap: (tabIndex) {},
                labelColor: Colors.white,
                indicatorColor: Colors.white,
                tabs: const <Widget>[
                  Tab(icon: Icon(Icons.flight), child: Text('Flight')),
                  Tab(icon: Icon(Icons.map), child: Text('Map')),
                  Tab(icon: Icon(Icons.print), child: Text('Print')),
                ],
              ),
            ),
            body: SafeArea(
              child: TabBarView(
                children: <Widget>[
                  HomePage(),
                  HomePage(),
                  HomePage(),
                ],
              ),
            ),
            bottomNavigationBar: BottomAppBar(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
// *** PROBLEM 1 IS HERE ***
                  Text('${_pageIndex.index}'),
                ],
              ),
            ),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class HomePage extends StatefulWidget {
      @override
      _HomePageState createState() => _HomePageState();
    }

    class _HomePageState extends State<HomePage> {
      List<Widget> cards = [];

      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        for (var index = 0; index < 7; index++) {
          cards.add(
            Center(
              child: Text(
                '$index',
                style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
              ),
            ),
          );
          print(index);
        }
        return PageView(
          onPageChanged: (index) {
            setState(() {
//*** PROBLEM 2 IS HERE ***
              _pageIndex.index = index.toDouble();
              print('page index: ${_pageIndex.index}');
            });
          },
          children: cards,
        );
      }
    }

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/page_menu.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Testing Inherited Widgets',
      home: ChangeNotifierProvider(
        create: (BuildContext context) => Counter(0),
        child: MenuPage(),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int _counter;

  Counter(this._counter);

  getCounter() => _counter;

  setCounter(int counter) => _counter = counter;

  void increment(int counter) {
    _counter = counter;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/home_page.dart';

class MenuPage extends StatefulWidget {
  @override
  _MenuPageState createState() => _MenuPageState();
}

class _MenuPageState extends State<MenuPage> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return DefaultTabController(
      length: 3,
      child: Scaffold(
        //TODO: dot indicator
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Center(
            child: Text('Testing Inherited Widgets',
                style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
          ),
          bottom: TabBar(
            onTap: (tabIndex) {
              counter.increment(0);
            },
            labelColor: Colors.white,
            indicatorColor: Colors.white,
            tabs: const <Widget>[
              Tab(icon: Icon(Icons.flight), child: Text('Flight')),
              Tab(icon: Icon(Icons.map), child: Text('Map')),
              Tab(icon: Icon(Icons.print), child: Text('Print')),
            ],
          ),
        ),
        body: SafeArea(
          child: TabBarView(
            children: <Widget>[
              HomePage(),
              HomePage(),
              HomePage(),
            ],
          ),
        ),
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              //TODO: insert value below.
              Text(counter.getCounter().toString()),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> cards = [];

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    for (var index = 0; index < 7; index++) {
      cards.add(
        Center(
          child: Text(
            '$index',
            style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
          ),
        ),
      );
      print(index);
    }
    return PageView(
      onPageChanged: (index) {
        setState(() {
          counter.increment(index);
        });
      },
      children: cards,
    );
  }
}
菜单页面。省道

import 'package:flutter/material.dart';

    class PageIndex {
      PageIndex({@required this.index});
      double index = 0;
    }

import 'package:flutter/cupertino.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';

class InheritedPageIndex extends InheritedWidget {
  InheritedPageIndex({Key key, @required this.indexData, Widget child})
      : super(key: key, child: child);

  final PageIndex indexData;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => true;

  static PageIndex of(BuildContext context) => context
      .dependOnInheritedWidgetOfExactType<InheritedPageIndex>()
      .indexData;
}

import 'package:flutter/material.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';
import 'package:testinginheritedwidget/pages/menu_page.dart';
import 'package:testinginheritedwidget/providers/page_index_provider.dart';

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

    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return InheritedPageIndex(
          indexData: PageIndex(index: 0),
          child: MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Testing Inherited Widgets',
            home: MenuPage(),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/pages/home_page.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class MenuPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        return DefaultTabController(
          length: 3,
          child: Scaffold(
            //TODO: dot indicator
            resizeToAvoidBottomInset: false,
            appBar: AppBar(
              backgroundColor: Colors.black,
              title: Center(
                child: Text('Testing Inherited Widgets',
                    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
              ),
              bottom: TabBar(
                onTap: (tabIndex) {},
                labelColor: Colors.white,
                indicatorColor: Colors.white,
                tabs: const <Widget>[
                  Tab(icon: Icon(Icons.flight), child: Text('Flight')),
                  Tab(icon: Icon(Icons.map), child: Text('Map')),
                  Tab(icon: Icon(Icons.print), child: Text('Print')),
                ],
              ),
            ),
            body: SafeArea(
              child: TabBarView(
                children: <Widget>[
                  HomePage(),
                  HomePage(),
                  HomePage(),
                ],
              ),
            ),
            bottomNavigationBar: BottomAppBar(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
// *** PROBLEM 1 IS HERE ***
                  Text('${_pageIndex.index}'),
                ],
              ),
            ),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class HomePage extends StatefulWidget {
      @override
      _HomePageState createState() => _HomePageState();
    }

    class _HomePageState extends State<HomePage> {
      List<Widget> cards = [];

      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        for (var index = 0; index < 7; index++) {
          cards.add(
            Center(
              child: Text(
                '$index',
                style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
              ),
            ),
          );
          print(index);
        }
        return PageView(
          onPageChanged: (index) {
            setState(() {
//*** PROBLEM 2 IS HERE ***
              _pageIndex.index = index.toDouble();
              print('page index: ${_pageIndex.index}');
            });
          },
          children: cards,
        );
      }
    }

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/page_menu.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Testing Inherited Widgets',
      home: ChangeNotifierProvider(
        create: (BuildContext context) => Counter(0),
        child: MenuPage(),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int _counter;

  Counter(this._counter);

  getCounter() => _counter;

  setCounter(int counter) => _counter = counter;

  void increment(int counter) {
    _counter = counter;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/home_page.dart';

class MenuPage extends StatefulWidget {
  @override
  _MenuPageState createState() => _MenuPageState();
}

class _MenuPageState extends State<MenuPage> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return DefaultTabController(
      length: 3,
      child: Scaffold(
        //TODO: dot indicator
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Center(
            child: Text('Testing Inherited Widgets',
                style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
          ),
          bottom: TabBar(
            onTap: (tabIndex) {
              counter.increment(0);
            },
            labelColor: Colors.white,
            indicatorColor: Colors.white,
            tabs: const <Widget>[
              Tab(icon: Icon(Icons.flight), child: Text('Flight')),
              Tab(icon: Icon(Icons.map), child: Text('Map')),
              Tab(icon: Icon(Icons.print), child: Text('Print')),
            ],
          ),
        ),
        body: SafeArea(
          child: TabBarView(
            children: <Widget>[
              HomePage(),
              HomePage(),
              HomePage(),
            ],
          ),
        ),
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              //TODO: insert value below.
              Text(counter.getCounter().toString()),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> cards = [];

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    for (var index = 0; index < 7; index++) {
      cards.add(
        Center(
          child: Text(
            '$index',
            style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
          ),
        ),
      );
      print(index);
    }
    return PageView(
      onPageChanged: (index) {
        setState(() {
          counter.increment(index);
        });
      },
      children: cards,
    );
  }
}

导入“包装：颤振/材料.省道”；
导入“package:testinginheritedwidget/models/page_index_model.dart”；
导入“package:testinginheritedwidget/pages/home_page.dart”；
导入“包：testinginheritedwidget/providers/page_index_provider.dart”；
类MenuPage扩展了无状态小部件{
@凌驾
小部件构建（构建上下文）{
PageIndex _PageIndex=InheritedPageIndex.of（上下文）；
返回DefaultTabController(
长度：3，
孩子：脚手架(
//TODO:点指示器
resizeToAvoidBottomInset:false，
appBar:appBar(
背景颜色：Colors.black，
标题：中心(
子：文本（'测试继承的小部件'，
样式：TextStyle（fontSize:20.0，fontWeight:fontWeight.bold）），
),
底部：选项卡栏(
onTap：（tabIndex）{}，
labelColor:Colors.white，
指示颜色：颜色。白色，
制表符：常数[
选项卡（图标：图标（Icons.flight），子项：文本（“flight”），
选项卡（图标：图标（Icons.map），子项：文本（'map'），
选项卡（图标：图标（Icons.print），子项：文本（“print”），
],
),
),
正文：安全区(
子项：选项卡视图(
儿童：[
首页（），
首页（），
首页（），
],
),
),
bottomNavigationBar:BottomAppBar(
孩子：排(
mainAxisAlignment:mainAxisAlignment.center，
儿童：[
//***问题1在这里***
文本（“${u pageIndex.index}”），
],
),
),
),
);
}
}
主页.省道

import 'package:flutter/material.dart';

    class PageIndex {
      PageIndex({@required this.index});
      double index = 0;
    }

import 'package:flutter/cupertino.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';

class InheritedPageIndex extends InheritedWidget {
  InheritedPageIndex({Key key, @required this.indexData, Widget child})
      : super(key: key, child: child);

  final PageIndex indexData;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => true;

  static PageIndex of(BuildContext context) => context
      .dependOnInheritedWidgetOfExactType<InheritedPageIndex>()
      .indexData;
}

import 'package:flutter/material.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';
import 'package:testinginheritedwidget/pages/menu_page.dart';
import 'package:testinginheritedwidget/providers/page_index_provider.dart';

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

    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return InheritedPageIndex(
          indexData: PageIndex(index: 0),
          child: MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Testing Inherited Widgets',
            home: MenuPage(),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/pages/home_page.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class MenuPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        return DefaultTabController(
          length: 3,
          child: Scaffold(
            //TODO: dot indicator
            resizeToAvoidBottomInset: false,
            appBar: AppBar(
              backgroundColor: Colors.black,
              title: Center(
                child: Text('Testing Inherited Widgets',
                    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
              ),
              bottom: TabBar(
                onTap: (tabIndex) {},
                labelColor: Colors.white,
                indicatorColor: Colors.white,
                tabs: const <Widget>[
                  Tab(icon: Icon(Icons.flight), child: Text('Flight')),
                  Tab(icon: Icon(Icons.map), child: Text('Map')),
                  Tab(icon: Icon(Icons.print), child: Text('Print')),
                ],
              ),
            ),
            body: SafeArea(
              child: TabBarView(
                children: <Widget>[
                  HomePage(),
                  HomePage(),
                  HomePage(),
                ],
              ),
            ),
            bottomNavigationBar: BottomAppBar(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
// *** PROBLEM 1 IS HERE ***
                  Text('${_pageIndex.index}'),
                ],
              ),
            ),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class HomePage extends StatefulWidget {
      @override
      _HomePageState createState() => _HomePageState();
    }

    class _HomePageState extends State<HomePage> {
      List<Widget> cards = [];

      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        for (var index = 0; index < 7; index++) {
          cards.add(
            Center(
              child: Text(
                '$index',
                style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
              ),
            ),
          );
          print(index);
        }
        return PageView(
          onPageChanged: (index) {
            setState(() {
//*** PROBLEM 2 IS HERE ***
              _pageIndex.index = index.toDouble();
              print('page index: ${_pageIndex.index}');
            });
          },
          children: cards,
        );
      }
    }

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/page_menu.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Testing Inherited Widgets',
      home: ChangeNotifierProvider(
        create: (BuildContext context) => Counter(0),
        child: MenuPage(),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int _counter;

  Counter(this._counter);

  getCounter() => _counter;

  setCounter(int counter) => _counter = counter;

  void increment(int counter) {
    _counter = counter;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/home_page.dart';

class MenuPage extends StatefulWidget {
  @override
  _MenuPageState createState() => _MenuPageState();
}

class _MenuPageState extends State<MenuPage> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return DefaultTabController(
      length: 3,
      child: Scaffold(
        //TODO: dot indicator
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Center(
            child: Text('Testing Inherited Widgets',
                style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
          ),
          bottom: TabBar(
            onTap: (tabIndex) {
              counter.increment(0);
            },
            labelColor: Colors.white,
            indicatorColor: Colors.white,
            tabs: const <Widget>[
              Tab(icon: Icon(Icons.flight), child: Text('Flight')),
              Tab(icon: Icon(Icons.map), child: Text('Map')),
              Tab(icon: Icon(Icons.print), child: Text('Print')),
            ],
          ),
        ),
        body: SafeArea(
          child: TabBarView(
            children: <Widget>[
              HomePage(),
              HomePage(),
              HomePage(),
            ],
          ),
        ),
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              //TODO: insert value below.
              Text(counter.getCounter().toString()),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> cards = [];

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    for (var index = 0; index < 7; index++) {
      cards.add(
        Center(
          child: Text(
            '$index',
            style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
          ),
        ),
      );
      print(index);
    }
    return PageView(
      onPageChanged: (index) {
        setState(() {
          counter.increment(index);
        });
      },
      children: cards,
    );
  }
}

导入“包装：颤振/材料.省道”；
导入“package:testinginheritedwidget/models/page_index_model.dart”；
导入“包：testinginheritedwidget/providers/page_index_provider.dart”；
类主页扩展了StatefulWidget{
@凌驾
_HomePageState createState（）=>\u HomePageState（）；
}
类_HomePageState扩展状态{
列表卡=[]；
@凌驾
小部件构建（构建上下文）{
PageIndex _PageIndex=InheritedPageIndex.of（上下文）；
对于（var指数=0；指数<7；指数++）{
卡片。添加(
居中(
子：文本(
“$index”，
样式：TextStyle（fontSize:25，fontWeight:fontWeight.bold），
),
),
);
打印（索引）；
}
返回页面视图(
onPageChanged:（索引）{
设置状态（）{
//***问题2在这里***
_pageIndex.index=index.toDouble（）；
打印（'页面索引：${u pageIndex.index}'）；
});
},
孩子们：卡片，
);
}
}
假设：经过大量研究和思考。我相信我无法更新供应商的价值；因为它位于第一个实例化的InheritedWidget和更改状态的方法之间。也许另一种说法是，我想要改变的状态就在它的正上方；并且，它采用第二个提供者的状态，而不是使用第一个提供者的状态

问题：

1）为了我的利益，我的假设是正确的，还是这里发生了其他事情

2）我该如何解决我的问题？我不相信实现一个BLoC方法能够解决这个问题，因为它也使用了一个提供者

我不知道在没有InheritedWidget的情况下如何将状态传递到widget树上。

您应该检查这个包：它是InheritedWidget的包装。并检查暴露
更改通知程序
类并允许在更新时通知侦听器的。如果您需要更多说明，我可以为您提供带软件包的解决方案

简介：为了全面起见，我将代码作为使用提供者软件包的最终答案，正如上面评论中所建议的那样。正如您所期望的，这段代码比上面的答案更简单，因为上面的答案不使用包

代码：

main.dart

import 'package:flutter/material.dart';

    class PageIndex {
      PageIndex({@required this.index});
      double index = 0;
    }

import 'package:flutter/cupertino.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';

class InheritedPageIndex extends InheritedWidget {
  InheritedPageIndex({Key key, @required this.indexData, Widget child})
      : super(key: key, child: child);

  final PageIndex indexData;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => true;

  static PageIndex of(BuildContext context) => context
      .dependOnInheritedWidgetOfExactType<InheritedPageIndex>()
      .indexData;
}

import 'package:flutter/material.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';
import 'package:testinginheritedwidget/pages/menu_page.dart';
import 'package:testinginheritedwidget/providers/page_index_provider.dart';

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

    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return InheritedPageIndex(
          indexData: PageIndex(index: 0),
          child: MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Testing Inherited Widgets',
            home: MenuPage(),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/pages/home_page.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class MenuPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        return DefaultTabController(
          length: 3,
          child: Scaffold(
            //TODO: dot indicator
            resizeToAvoidBottomInset: false,
            appBar: AppBar(
              backgroundColor: Colors.black,
              title: Center(
                child: Text('Testing Inherited Widgets',
                    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
              ),
              bottom: TabBar(
                onTap: (tabIndex) {},
                labelColor: Colors.white,
                indicatorColor: Colors.white,
                tabs: const <Widget>[
                  Tab(icon: Icon(Icons.flight), child: Text('Flight')),
                  Tab(icon: Icon(Icons.map), child: Text('Map')),
                  Tab(icon: Icon(Icons.print), child: Text('Print')),
                ],
              ),
            ),
            body: SafeArea(
              child: TabBarView(
                children: <Widget>[
                  HomePage(),
                  HomePage(),
                  HomePage(),
                ],
              ),
            ),
            bottomNavigationBar: BottomAppBar(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
// *** PROBLEM 1 IS HERE ***
                  Text('${_pageIndex.index}'),
                ],
              ),
            ),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class HomePage extends StatefulWidget {
      @override
      _HomePageState createState() => _HomePageState();
    }

    class _HomePageState extends State<HomePage> {
      List<Widget> cards = [];

      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        for (var index = 0; index < 7; index++) {
          cards.add(
            Center(
              child: Text(
                '$index',
                style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
              ),
            ),
          );
          print(index);
        }
        return PageView(
          onPageChanged: (index) {
            setState(() {
//*** PROBLEM 2 IS HERE ***
              _pageIndex.index = index.toDouble();
              print('page index: ${_pageIndex.index}');
            });
          },
          children: cards,
        );
      }
    }

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/page_menu.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Testing Inherited Widgets',
      home: ChangeNotifierProvider(
        create: (BuildContext context) => Counter(0),
        child: MenuPage(),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int _counter;

  Counter(this._counter);

  getCounter() => _counter;

  setCounter(int counter) => _counter = counter;

  void increment(int counter) {
    _counter = counter;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/home_page.dart';

class MenuPage extends StatefulWidget {
  @override
  _MenuPageState createState() => _MenuPageState();
}

class _MenuPageState extends State<MenuPage> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return DefaultTabController(
      length: 3,
      child: Scaffold(
        //TODO: dot indicator
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Center(
            child: Text('Testing Inherited Widgets',
                style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
          ),
          bottom: TabBar(
            onTap: (tabIndex) {
              counter.increment(0);
            },
            labelColor: Colors.white,
            indicatorColor: Colors.white,
            tabs: const <Widget>[
              Tab(icon: Icon(Icons.flight), child: Text('Flight')),
              Tab(icon: Icon(Icons.map), child: Text('Map')),
              Tab(icon: Icon(Icons.print), child: Text('Print')),
            ],
          ),
        ),
        body: SafeArea(
          child: TabBarView(
            children: <Widget>[
              HomePage(),
              HomePage(),
              HomePage(),
            ],
          ),
        ),
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              //TODO: insert value below.
              Text(counter.getCounter().toString()),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> cards = [];

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    for (var index = 0; index < 7; index++) {
      cards.add(
        Center(
          child: Text(
            '$index',
            style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
          ),
        ),
      );
      print(index);
    }
    return PageView(
      onPageChanged: (index) {
        setState(() {
          counter.increment(index);
        });
      },
      children: cards,
    );
  }
}
计数器\u型号.省道

import 'package:flutter/material.dart';

    class PageIndex {
      PageIndex({@required this.index});
      double index = 0;
    }

import 'package:flutter/cupertino.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';

class InheritedPageIndex extends InheritedWidget {
  InheritedPageIndex({Key key, @required this.indexData, Widget child})
      : super(key: key, child: child);

  final PageIndex indexData;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => true;

  static PageIndex of(BuildContext context) => context
      .dependOnInheritedWidgetOfExactType<InheritedPageIndex>()
      .indexData;
}

import 'package:flutter/material.dart';
import 'package:testinginheritedwidget/models/page_index_model.dart';
import 'package:testinginheritedwidget/pages/menu_page.dart';
import 'package:testinginheritedwidget/providers/page_index_provider.dart';

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

    class App extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return InheritedPageIndex(
          indexData: PageIndex(index: 0),
          child: MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Testing Inherited Widgets',
            home: MenuPage(),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/pages/home_page.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class MenuPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        return DefaultTabController(
          length: 3,
          child: Scaffold(
            //TODO: dot indicator
            resizeToAvoidBottomInset: false,
            appBar: AppBar(
              backgroundColor: Colors.black,
              title: Center(
                child: Text('Testing Inherited Widgets',
                    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
              ),
              bottom: TabBar(
                onTap: (tabIndex) {},
                labelColor: Colors.white,
                indicatorColor: Colors.white,
                tabs: const <Widget>[
                  Tab(icon: Icon(Icons.flight), child: Text('Flight')),
                  Tab(icon: Icon(Icons.map), child: Text('Map')),
                  Tab(icon: Icon(Icons.print), child: Text('Print')),
                ],
              ),
            ),
            body: SafeArea(
              child: TabBarView(
                children: <Widget>[
                  HomePage(),
                  HomePage(),
                  HomePage(),
                ],
              ),
            ),
            bottomNavigationBar: BottomAppBar(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
// *** PROBLEM 1 IS HERE ***
                  Text('${_pageIndex.index}'),
                ],
              ),
            ),
          ),
        );
      }
    }

    import 'package:flutter/material.dart';
    import 'package:testinginheritedwidget/models/page_index_model.dart';
    import 'package:testinginheritedwidget/providers/page_index_provider.dart';

    class HomePage extends StatefulWidget {
      @override
      _HomePageState createState() => _HomePageState();
    }

    class _HomePageState extends State<HomePage> {
      List<Widget> cards = [];

      @override
      Widget build(BuildContext context) {
        PageIndex _pageIndex = InheritedPageIndex.of(context);

        for (var index = 0; index < 7; index++) {
          cards.add(
            Center(
              child: Text(
                '$index',
                style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
              ),
            ),
          );
          print(index);
        }
        return PageView(
          onPageChanged: (index) {
            setState(() {
//*** PROBLEM 2 IS HERE ***
              _pageIndex.index = index.toDouble();
              print('page index: ${_pageIndex.index}');
            });
          },
          children: cards,
        );
      }
    }

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/page_menu.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Testing Inherited Widgets',
      home: ChangeNotifierProvider(
        create: (BuildContext context) => Counter(0),
        child: MenuPage(),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int _counter;

  Counter(this._counter);

  getCounter() => _counter;

  setCounter(int counter) => _counter = counter;

  void increment(int counter) {
    _counter = counter;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';
import 'package:stackoverflowquestionthree/home_page.dart';

class MenuPage extends StatefulWidget {
  @override
  _MenuPageState createState() => _MenuPageState();
}

class _MenuPageState extends State<MenuPage> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    return DefaultTabController(
      length: 3,
      child: Scaffold(
        //TODO: dot indicator
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: Colors.black,
          title: Center(
            child: Text('Testing Inherited Widgets',
                style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.bold)),
          ),
          bottom: TabBar(
            onTap: (tabIndex) {
              counter.increment(0);
            },
            labelColor: Colors.white,
            indicatorColor: Colors.white,
            tabs: const <Widget>[
              Tab(icon: Icon(Icons.flight), child: Text('Flight')),
              Tab(icon: Icon(Icons.map), child: Text('Map')),
              Tab(icon: Icon(Icons.print), child: Text('Print')),
            ],
          ),
        ),
        body: SafeArea(
          child: TabBarView(
            children: <Widget>[
              HomePage(),
              HomePage(),
              HomePage(),
            ],
          ),
        ),
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              //TODO: insert value below.
              Text(counter.getCounter().toString()),
            ],
          ),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stackoverflowquestionthree/counter_model.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> cards = [];

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<Counter>(context);

    for (var index = 0; index < 7; index++) {
      cards.add(
        Center(
          child: Text(
            '$index',
            style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
          ),
        ),
      );
      print(index);
    }
    return PageView(
      onPageChanged: (index) {
        setState(() {
          counter.increment(index);
        });
      },
      children: cards,
    );
  }
}
页面菜单。省道