这个答案将涵盖向前传递数据和向后传递数据。与 Android 活动和 iOS 视图控制器不同，Flutter 中的不同屏幕只是小部件。在它们之间导航涉及创建称为路由的东西，并使用将Navigator路由推入和弹出堆栈。

将数据转发到下一个屏幕

要将数据发送到下一个屏幕，请执行以下操作：

使SecondScreen构造函数接受您要发送给它的数据类型的参数。在此特定示例中，数据被定义为一个String值，并在此处设置为this.text。
```
class SecondScreen extends StatelessWidget {
  final String text;
  SecondScreen({Key key, @required this.text}) : super(key: key);

  ...
```
然后使用小部件Navigator中FirstScreen的将路由推送到SecondScreen小部件。您将要发送的数据作为参数放入其构造函数中。
```
Navigator.push(
    context,
    MaterialPageRoute(
      builder: (context) => SecondScreen(text: 'Hello',),
    ));
```

完整的代码在main.dart这里：

import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    title: 'Flutter',
    home: FirstScreen(),
  ));
}

class FirstScreen extends StatefulWidget {
  @override
  _FirstScreenState createState() {
    return _FirstScreenState();
  }
}

class _FirstScreenState extends State<FirstScreen> {

  // this allows us to access the TextField text
  TextEditingController textFieldController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('First screen')),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [

          Padding(
            padding: const EdgeInsets.all(32.0),
            child: TextField(
              controller: textFieldController,
              style: TextStyle(
                fontSize: 24,
                color: Colors.black,
              ),
            ),
          ),

          RaisedButton(
            child: Text(
              'Go to second screen',
              style: TextStyle(fontSize: 24),
            ),
            onPressed: () {
              _sendDataToSecondScreen(context);
            },
          )

        ],
      ),
    );
  }

  // get the text in the TextField and start the Second Screen
  void _sendDataToSecondScreen(BuildContext context) {
    String textToSend = textFieldController.text;
    Navigator.push(
        context,
        MaterialPageRoute(
          builder: (context) => SecondScreen(text: textToSend,),
        ));
  }
}

class SecondScreen extends StatelessWidget {
  final String text;

  // receive data from the FirstScreen as a parameter
  SecondScreen({Key key, @required this.text}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Second screen')),
      body: Center(
        child: Text(
          text,
          style: TextStyle(fontSize: 24),
        ),
      ),
    );
  }
}

将数据传回前一个屏幕

传回数据时，您需要执行以下操作：

在中FirstScreen，使用Navigator推入（启动）SecondScreen方法async并等待它完成时返回的结果。

final result = await Navigator.push(
    context,
    MaterialPageRoute(
      builder: (context) => SecondScreen(),
    ));

在中SecondScreen，包含您想要在弹出时作为参数传回的数据Navigator。
```
Navigator.pop(context, 'Hello');
```
然后在FirstScreen将await完成，您可以使用结果。
```
setState(() {
  text = result;
});
```

这是main.dart供您参考的完整代码。

import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    title: 'Flutter',
    home: FirstScreen(),
  ));
}

class FirstScreen extends StatefulWidget {
  @override
  _FirstScreenState createState() {
    return _FirstScreenState();
  }
}

class _FirstScreenState extends State<FirstScreen> {

  String text = 'Text';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('First screen')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [

            Padding(
              padding: const EdgeInsets.all(32.0),
              child: Text(
                text,
                style: TextStyle(fontSize: 24),
              ),
            ),

            RaisedButton(
              child: Text(
                'Go to second screen',
                style: TextStyle(fontSize: 24),
              ),
              onPressed: () {
                _awaitReturnValueFromSecondScreen(context);
              },
            )

          ],
        ),
      ),
    );
  }

  void _awaitReturnValueFromSecondScreen(BuildContext context) async {

    // start the SecondScreen and wait for it to finish with a result
    final result = await Navigator.push(
        context,
        MaterialPageRoute(
          builder: (context) => SecondScreen(),
        ));

    // after the SecondScreen result comes back update the Text widget with it
    setState(() {
      text = result;
    });
  }
}

class SecondScreen extends StatefulWidget {
  @override
  _SecondScreenState createState() {
    return _SecondScreenState();
  }
}

class _SecondScreenState extends State<SecondScreen> {
  // this allows us to access the TextField text
  TextEditingController textFieldController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Second screen')),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [

          Padding(
            padding: const EdgeInsets.all(32.0),
            child: TextField(
              controller: textFieldController,
              style: TextStyle(
                fontSize: 24,
                color: Colors.black,
              ),
            ),
          ),

          RaisedButton(
            child: Text(
              'Send text back',
              style: TextStyle(fontSize: 24),
            ),
            onPressed: () {
              _sendDataBack(context);
            },
          )

        ],
      ),
    );
  }

  // get the text in the TextField and send it back to the FirstScreen
  void _sendDataBack(BuildContext context) {
    String textToSendBack = textFieldController.text;
    Navigator.pop(context, textToSendBack);
  }
}

dart - 在 Flutter 中的屏幕之间传递数据

问题描述

解决方案

将数据转发到下一个屏幕

将数据传回前一个屏幕

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