我尝试创建一个基本的笔记应用程序来研究 flutter，但我不太明白如何通知我的 NotesContainer 按钮已被按下。我试图为它创建一个引用，但是添加函数在我不确定如何到达的状态类中。

import 'package:flutter/material.dart';

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final NotesContainer Notes = new NotesContainer();
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: Text('My Notes'),
        backgroundColor: Color.fromRGBO(223, 175, 117, 1),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.add),
            onPressed: (){
              Notes.add()
            },
          )
        ],
      ),
      body: Notes
    );
  }
}

class NoteData{
  String title;
  String content;

  NoteData(this.title, this.content);
  NoteData.noContent(t){
    title = t;
    content ='';
  }
}

class NotesContainer extends StatefulWidget{
  @override

  State<StatefulWidget> createState(){
    return new _NotesContainer();
  }

}

class _NotesContainer extends State<NotesContainer>{
  final _notes = <NoteData>[new NoteData('title','thing to do'), new NoteData('title2','thing to do2')];

  void add({String title='1'}){ //just to test adding 
    setState(() {
       _notes.add(new NoteData.noContent(title));
    });
  }

  Widget build(BuildContext context){
    return _buildNotesContainer();
  }

  _buildNotesContainer(){

    return new ListView.separated(
      itemCount: _notes.length,
      separatorBuilder: (BuildContext context, int index) => Divider(),
      itemBuilder: (BuildContext context, int index) {
        return ListTile(
          title: Text(_notes[index].title), 
        );
      },
      padding: const EdgeInsets.all(10.0),
    );
  }
}

我想解决方案是以某种方式通过有状态的 NotesContainer 类公开 _NotesContainer 中的 _function。我想知道是否有更优雅的解决方案。

谢谢，或者

最佳答案

我认为将在小部件树中进一步添加元素的责任委派更有意义。我修改了您的代码以展示其工作原理。

但是，如果您最终得到一个很深的小部件树并且子小部件需要 _notes 列表，那么我建议您考虑使用 Inherited 小部件并将 _notes 列表添加到它，这样您就可以访问它而无需通过状态太多了。

import 'package:flutter/material.dart';

// Note the name change
class NotesPage extends StatefulWidget {

  @override
  _NotesPageState createState() => _NotesPageState();
}

class _NotesPageState extends State<NotesPage> {
  final List<NoteData> _notes = <NoteData>[NoteData('title','thing to do'), NoteData('title2','thing to do2')];

  void add({String title='1'}){ //just to test adding
    setState(() {
      _notes.add(NoteData.noContent(title));
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          centerTitle: true,
          title: Text('My Notes'),
          backgroundColor: Color.fromRGBO(223, 175, 117, 1),
          actions: <Widget>[
            IconButton(
              icon: Icon(Icons.add),
              onPressed: (){
                add();
              },
            )
          ],
        ),
        body: NotesContainer(notes: _notes)
    );
  }
}

class NoteData{
  String title;
  String content;

  NoteData(this.title, this.content);
  NoteData.noContent(t){
    title = t;
    content ='';
  }
}

class NotesContainer extends StatelessWidget{
  final List<NoteData> notes;

  const NotesContainer({Key key, this.notes}) : super(key: key);

  @override
  Widget build(BuildContext context){
    return ListView.separated(
      itemCount: notes.length,
      separatorBuilder: (BuildContext context, int index) => Divider(),
      itemBuilder: (BuildContext context, int index) {
        return ListTile(
          title: Text(notes[index].title),
        );
      },
      padding: const EdgeInsets.all(10.0),
    );
  }
}

希望对您有所帮助:-)

关于flutter - 从父访问状态 - flutter，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55828730/