这个答案将包括向前传递数据和向后传递数据.与Android Activities和iOS ViewController不同,Flatter中的不同屏幕只是小部件.在它们之间导航需要创建一个称为路由的东西,并使用Navigator
在堆栈上推送和弹出路由.
要将数据发送到下一个屏幕,请执行以下操作:
使SecondScreen
构造函数接受要发送给它的数据类型的参数.在该特定示例中,数据被定义为String
值,并且在这里设置为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.您将想要作为参数发送的数据放入其构造函数中.
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => SecondScreen(text: 'Hello',),
));
main.dart
的完整代码如下:
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),
),
),
);
}
}
在传回数据时,您需要执行以下操作:
在FirstScreen
中,使用Navigator
在async
方法中推送(启动)SecondScreen
,并等待它完成时返回的结果.
final result = await Navigator.push(
context,
MaterialPageRoute(
builder: (context) => SecondScreen(),
));
在SecondScreen
中,包括弹出Navigator
时要作为参数传回的数据.
Navigator.pop(context, 'Hello');
然后,在FirstScreen
米中,await
将结束,您可以使用结果.
setState(() {
text = result;
});
下面是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);
}
}