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Navigator 将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，数据定义为 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FirstScreen 小部件中的Navigator 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',),
));
main.dart 的完整代码在这里：
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),
),
),
);
}
}
将数据传回前一屏幕
在传回数据时，您需要做以下事情：
-
在FirstScreen 中，使用Navigator 在async 方法中推送（启动）SecondScreen，并等待它完成后返回的结果。
final result = await Navigator.push(
context,
MaterialPageRoute(
builder: (context) => SecondScreen(),
));
-
在SecondScreen 中，包含您要在弹出Navigator 时作为参数传回的数据。
Navigator.pop(context, 'Hello');
-
然后在FirstScreen await 将完成，您可以使用结果。
setState(() {
text = result;
});
这是main.dart的完整代码供您参考。
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);
}
}