Question

我试图在动态范围内实现动态主题。我尝试了以下一些教程和文档。最后，我了解到它将涉及到使用InheritedWidget，因此我尝试从Flutter文档以及此处进行研究。

Flutter: How to correctly use an Inherited Widget?

所以我停留在两个地方。其中之一是如何在MyAppState中更改ThemeData，以及如何在构建MaterialApp时访问该主题数据

还有另外一件事，我必须在哪里使用MyApp.of（context），我在某处尝试了此语句，但这会导致错误

获取器“数据”在null上被调用。

我试图从任何位于MaterialApp内部深处的小部件动态更改ThemeData

我尝试过的是：

import 'package:flutter/material.dart';
void main() => runApp(MainApp());

class _MyInherited extends InheritedWidget {
  final MyAppState data;

  _MyInherited({Key key, this.data, Widget child})
      : super(key: key, child: child);

  @override
  bool updateShouldNotify(_MyInherited old) {
    return true;
  }
}

class MyApp extends StatefulWidget {
  Widget child;

  MyApp({this.child});

  @override
  State<StatefulWidget> createState() {
    return MyAppState();
  }

  static MyAppState of(BuildContext context) {
    return (context.inheritFromWidgetOfExactType(_MyInherited) as _MyInherited)
        .data;
  }
}

class MyAppState extends State<MyApp> {
  ThemeData _myField;
  // only expose a getter to prevent bad usage
  ThemeData get myField => _myField;

  void onMyFieldChange(ThemeData newValue) {
    setState(() {
      _myField = newValue;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new _MyInherited(
      data: this,
      child: widget.child,
    );
  }
}


class MainApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MyApp(
      child: MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(primaryColor: Color(0xFFFFFF).withAlpha(0xFF);), //This is the themeData which I have to change from any widget inside MaterialApp
        home: Container(height: 200, width: 200, color: Colors.green)
          ),
    );
  }
}

我应该怎么做？

flutter继承的小部件RootApp（材料应用）更改主题数据

0 个答案: