Question

我有一个TextField，需要输入可以编辑的起始文本，然后根据需要传递回或保存到设备中。

我使用TextEditingController()作为起始文字，并且正在努力从StatefulWidget的州内访问此值。

下面是我的代码：

class TextFieldScreen extends StatefulWidget {
  final initialText;
  const TextFieldScreen({Key key, this.initialText}) : super(key: key);

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

class _TextFieldScreenState extends State<TextFieldScreen> {

  final _controller = TextEditingController(text: widget.initialText);

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Container(
          padding: EdgeInsets.all(24.0),
          child: TextField(
            controller: _controller,
            decoration: InputDecoration(
              enabledBorder: OutlineInputBorder(
                borderSide: BorderSide(color: Colors.deepPurple),
                borderRadius: BorderRadius.all(Radius.circular(20.0))
              ),
              focusedBorder: OutlineInputBorder(
                  borderSide: BorderSide(color: Colors.red),
                  borderRadius: BorderRadius.all(Radius.circular(20.0))
              ),
            ),
          ),
        ),
      ],
    );
  }

在上面的代码中，final _controller = TextEditingController(text: widget.initialText);行出现了only static members can be accessed in initializers错误。

因此，在进行了一些搜索之后，我了解了为什么会发生这种情况，并且需要在initState()中进行初始化，因此我添加了以下代码：

      @override
      void initState() {
        super.initState();
        final _controller = TextEditingController(text: widget.initialText);
      }

现在以前的错误消失了，但是现在我的TextField()无法访问conroller:，而我却遇到了undefined错误。

这是解决这个问题的正确方法吗？

我该如何工作？

谢谢

Answer 1

您可以在下面复制粘贴运行完整代码
您可以在_controller之外声明initState
代码段

  TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = TextEditingController(text: widget.initialText);
  }

工作演示

完整代码

import 'package:flutter/material.dart';

class TextFieldScreen extends StatefulWidget {
  final initialText;
  const TextFieldScreen({Key key, this.initialText}) : super(key: key);

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

class _TextFieldScreenState extends State<TextFieldScreen> {
  TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = TextEditingController(text: widget.initialText);
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Container(
          padding: EdgeInsets.all(24.0),
          child: TextField(
            controller: _controller,
            decoration: InputDecoration(
              enabledBorder: OutlineInputBorder(
                  borderSide: BorderSide(color: Colors.deepPurple),
                  borderRadius: BorderRadius.all(Radius.circular(20.0))),
              focusedBorder: OutlineInputBorder(
                  borderSide: BorderSide(color: Colors.red),
                  borderRadius: BorderRadius.all(Radius.circular(20.0))),
            ),
          ),
        ),
      ],
    );
  }
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextFieldScreen(initialText: "abc",),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

如何将值从另一个屏幕传递到TextField的初始文本？

1 个答案: