listview - 如何将元素添加到另一个类中已经存在的列表中？

Question

我想用颤振制作一个待办事项列表应用程序，但是我无法将文本输入保存到已经在我显示的另一个类中创建的列表中。

我曾尝试使用 setter 在另一个类中创建一个对象，但由于我使用的是有状态小部件，因此这不起作用，特别是因为我在脚手架主体上使用 Lists() （列表视图）来显示列表项

这是我的列表视图类

import 'package:flutter/material.dart';
import 'todo.dart';

class TodoListS extends StatefulWidget {
  @override
  TodoList createState() => TodoList();
}
 class TodoList extends State<TodoListS> {
   List<Todo> todos = [Todo(title:'Checktheicon'), Todo(title: 'help me')];
   void setTodo(Todo todo)
   {
     todos.add(todo);
   }
      @override
      Widget build(BuildContext context) {

        return myListView(context,todos );
      }
    }

Widget myListView(BuildContext context, List<Todo> todos) {

      // backing data

      return ListView.builder(
        itemCount: todos.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(todos[index].title),
            leading: Icon(todos[index].icons),
          );
        },
      );

    }

这是我显示列表的地方

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
          backgroundColor: Colors.pink[100], title: new Text('Todo List')),
      body: TodoListS(),
      floatingActionButton: FloatingActionButton(
          child: Icon(Icons.add), onPressed: () =>  _displayDialog(context)),
    );
  }

这是我想要获取文本输入并保存它的地方

_displayDialog(BuildContext context) {
      return showDialog(
          context: context,
          builder: (context) {
            return AlertDialog(
              title: Text('Insert Your to do'),
              content: TextField(
                controller: _textFieldController,
                decoration: InputDecoration(hintText: "ie. Wash dishes"),
              ),
              actions: <Widget>[
                new FlatButton(
                  child: new Text('CANCEL'),
                  onPressed: () {
                    Navigator.of(context).pop();
                  },
                ),
                new FlatButton(
                  child: new Text('ADD'),
                  onPressed: () {
                  var todo = new Todo(title: _textFieldController.value.text);
                  todol.setTodo(todo);
                    Navigator.of(context).pop();
                  },
                )
              ],
            );
          });
    }

所以现在，什么都没有保存，唯一显示的是我之前创建的待办事项，我的文本输入需要添加到列表中才能显示。

标签： listviewinheritanceflutterdart

Answer 1

要调用另一个类中的函数，您可以使用 GlobalKey

第 1 步：定义final GlobalKey<TodoList> _key = GlobalKey();
第 2 步：在 onPressed 中使用 _key.currentState.setTodo(Todo(title: _textFieldController.text));
第 3 步：将密钥添加到类

class TodoListS extends StatefulWidget {
  TodoListS({Key key}) : super(key: key);

第 4 步：TodoListS 传递密钥

body: TodoListS(
        key: _key,
      ),

完整的工作代码

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  final _textFieldController = TextEditingController();
  final GlobalKey<TodoList> _key = GlobalKey();

  @override
  void dispose() {
    // Clean up the controller when the widget is removed from the
    // widget tree.
    _textFieldController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar:
          AppBar(backgroundColor: Colors.pink[100], title: Text('Todo List')),
      body: TodoListS(
        key: _key,
      ),
      floatingActionButton: FloatingActionButton(
          child: Icon(Icons.add), onPressed: () => _displayDialog(context)),
    );
  }

  _displayDialog(BuildContext context) {
    return showDialog(
        context: context,
        builder: (context) {
          return AlertDialog(
            title: Text('Insert Your to do'),
            content: TextField(
              controller: _textFieldController,
              decoration: InputDecoration(hintText: "ie. Wash dishes"),
            ),
            actions: <Widget>[
              FlatButton(
                child: Text('CANCEL'),
                onPressed: () {
                  Navigator.of(context).pop();
                },
              ),
              FlatButton(
                child: Text('ADD'),
                onPressed: () {
                  /*var todo =  Todo(title: _textFieldController.value.text);
                  todol.setTodo(todo);*/

                  _key.currentState
                      .setTodo(Todo(title: _textFieldController.text));
                  setState(() {

                  });
                  Navigator.of(context).pop();
                },
              )
            ],
          );
        });
  }
}

class Todo {
  String title;

  Todo({
    this.title,
  });

  factory Todo.fromJson(Map<String, dynamic> json) => Todo(
        title: json["title"] == null ? null : json["title"],
      );

  Map<String, dynamic> toJson() => {
        "title": title == null ? null : title,
      };
}

class TodoListS extends StatefulWidget {
  TodoListS({Key key}) : super(key: key);
  @override
  TodoList createState() => TodoList();
}

class TodoList extends State<TodoListS> {
  List<Todo> todos = [Todo(title: 'Checktheicon'), Todo(title: 'help me')];

  void setTodo(Todo todo) {
    todos.add(todo);
  }

  @override
  Widget build(BuildContext context) {
    return myListView(context, todos);
  }
}

Widget myListView(BuildContext context, List<Todo> todos) {
  // backing data
  return ListView.builder(
    itemCount: todos.length,
    itemBuilder: (context, index) {
      return ListTile(
        title: Text(todos[index].title),
        //leading: Icon(todos[index].icons),
      );
    },
  );
}

完整的工作演示