Flutter - 如何在其他小部件中访问 TextEditingController？

Question

我的 main.dart 中有一个 TextField，控制器名为 textcontroller。 在其他小部件（button.dart）中，我有一个按钮。如果我按下该按钮，它应该将 main.dart 中的 Text 小部件的文本设置为 TextField 的文本。只需执行与 main.dart 中的第一个按钮相同的操作即可。如何从其他小部件（文件）访问此 TextEditingController？

这是我的应用程序的视频，以便更好地理解。 https://streamable.com/xi0dn1

这是我的 main.dart 的完整代码

import 'button.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

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

  final String title;

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

class MyHomePageState extends State<MyHomePage> {
  String var1 = "text1";
  TextEditingController textController = TextEditingController();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("My app"),
      ),
      body: Center(
        child: Column(
          children: <Widget>[
            TextField(
              controller: textController,
            ),
            RaisedButton(
              child: Text("button in the same widget"),
              onPressed: () {
                setState(() {
                  var1 = textController.text;
                });
              },
            ),
            Text(var1),
            Button2(),
          ],
        ),
      ),
    );
  }
}

这是我的 button.dart 代码

import 'main.dart';

class Button2 extends StatefulWidget {
  @override
  _Button2State createState() => _Button2State();
}

class _Button2State extends State<Button2> {
  String var2 = "text2";

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        children: <Widget>[
          RaisedButton(
            child: Text("button in second widget"),
            onPressed: () {
              setState(() {
                var2 = MyHomePageState().textController.text.toString();
              });
            },
          ),
          Text(var2),
        ],
      ),
    );
  }
}

Answer 1

将函数与小部件分离并传递函数。

在我的主页状态中：

// Extract the function
void onPressedFunction() {
  setState(() {
    var1 =  textController.text;
  });
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    // ...
    child: Column(
      children: <Widget>[
        RaisedButton(
          // ...
          onPressed: onPressedFunction, // function is extracted
        ),
        Text(var1),
        Button2(onPressedFunction), // pass the function
      ],
    ),
  ); 
}

在 Button2 中：

class Button2 extends StatefulWidget {
  final Function onPressedFunction;

  Button2(this.onPressedFunction); // accept the function

  @override
  _Button2State createState() => _Button2State();
}

class _Button2State extends State<Button2> {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        children: <Widget>[
          RaisedButton(
            child: Text("button in second widget"),
            onPressed: widget.onPressedFunction, // use the same function
          ),
          Text(var2),
        ],
      ),
    );
  }
}

这样，您的 Button2 将执行与按下第一个按钮相同的操作。

Answer 2

您可以将MyHomePageState 类型的GlobalKey 用于MyHomePage，并将其传递给button2 的构造函数。使用GlobalKey，您可以调用相应小部件状态的方法。

ma​​in.dart：

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final GlobalKey<MyHomePageState> key = new GlobalKey(); // this is new
  final String title;

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

class MyHomePageState extends State<MyHomePage> {
  String var1 = "text1";
  TextEditingController textController = TextEditingController();
  
  @override
  void initState() {
    super.initState();
  }
  
  getText() { // this is new
    return textController.text; 
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("My app"),
      ),
      body: Center(
        child: Column(
          children: <Widget>[
            TextField(
              controller: textController,
            ),
            RaisedButton(
              child: Text("button in the same widget"),
              onPressed: () {
                setState(() {
                  var1 = textController.text;
                });
              },
            ),
            Text(var1),
            Button2(widget.key), // this has changed
          ],
        ),
      ),
    );
  }
}

button2.dart：

import 'package:flutter/material.dart';
import 'main.dart';
class Button2 extends StatefulWidget {
  final GlobalKey<MyHomePageState> homeKey; // this is new
  Button2(this.homeKey); // this is new
  @override
  _Button2State createState() => _Button2State();
}

class _Button2State extends State<Button2> {
  String var2 = "text2";

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        children: <Widget>[
          RaisedButton(
            child: Text("button in second widget"),
            onPressed: () {
              setState(() {
                var2 = widget.homeKey.currentState.getText(); // this is new
              });
            },
          ),
          Text(var2),
        ],
      ),
    );
  }
}