Flutter-使用pushName获取数据 [英] Flutter - Get data using pushName
本文介绍了Flutter-使用pushName获取数据的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在尝试使用pushName发送数据.然后，我尝试获取此数据以显示在Toast消息中.
PushName
Navigator.pushNamed(语境，'/航海家'，参数:< String，String> {'instalation':widget.instalation，'消息':DemoLocalizations.of(上下文).text('取消消息')+" +widget.datameterValue.toString()，}，); 尝试检索数据
类导航扩展了StatefulWidget {最终的ConnectionPage参数；导航({Key key，this.message，this.instalation，this.args}):super(key:key)；}类别_NavigationState扩展了State< Navigation>{无效的initState(){super.initState();打印(widget.args);//空值最后的便条= SnackBar(持续时间:持续时间(秒:5)，内容:文本(widget.args.messsage +'.'，textAlign:TextAlign.center)，backgroundColor:Colors.red [700]，);key.currentState.showSnackBar(snackBar);}} 问题:返回null.
所以:使用pushName获取数据的正确方法是什么?在文档中显示了如何在脚手架内部
完整代码
导入'package:flutter/material.dart';void main()=>runApp(MyApp());MyApp类扩展了StatelessWidget {@override窗口小部件build(BuildContext context){返回MaterialApp(//提供一个处理命名路由的函数.使用此功能可以//识别要推送的命名路由，并创建正确的路由//屏幕.路线:{'/extractArguments':(上下文)=>ExtractArgumentsScreen()，}，onGenerateRoute :(设置){//如果您按下PassArguments路线如果(settings.name == PassArgumentsScreen.routeName){//将参数强制转换为正确的类型:ScreenArguments.final ScreenArguments args = settings.arguments;//然后，从参数中提取所需的数据，然后//将数据传递到正确的屏幕.返回MaterialPageRoute(生成器:(上下文){返回PassArgumentsScreen(标题:args.title，讯息:args.message，);}，);}}，标题:带参数导航"，主页:HomeScreen()，);}}类HomeScreen扩展了StatelessWidget {@override窗口小部件build(BuildContext context){返回脚手架(appBar:AppBar(标题:文字(主屏幕")，)，身体:中心(子:列(mainAxisAlignment:MainAxisAlignment.center，子代:< Widget> [//导航到该路由的按钮.命名路线//本身提取参数.加高按钮(子级:Text(导航到提取参数的屏幕")，onPressed:(){//当用户点击按钮时，导航至特定路线//，并提供参数作为RouteSettings的一部分.Navigator.pushNamed(语境，ExtractArgumentsScreen.routeName，参数:{'instalation':"123"，"message":"456"}，);/*Navigator.push(语境，MaterialPageRoute(生成器:(上下文)=>ExtractArgumentsScreen()，//将参数作为RouteSettings的一部分传递.这//ExtractArgumentScreen从这些参数中读取参数//设置.设置:RouteSettings(参数:{'instalation':"123"，"message":"456"}，)，)，); */}，)，//导航到命名路线的按钮.对于此路线，提取//onGenerateRoute函数中的参数并将其传递//到屏幕.加高按钮(子级:Text(导航到接受参数的名称")，onPressed:(){//当用户点击按钮时，导航至命名路线//并提供参数作为可选参数.Navigator.pushNamed(语境，PassArgumentsScreen.routeName，参数:ScreenArguments(接受参数屏幕"，此消息是在onGenerateRoute函数中提取的."，)，);}，)，]，)，)，);}}//一个小部件，该小部件从ModalRoute中提取必要的参数.类ExtractArgumentsScreen扩展了StatefulWidget {静态const routeName ='/extractArguments';@override_ExtractArgumentsScreenState createState()=>_ExtractArgumentsScreenState();}类_ExtractArgumentsScreenState扩展了State< ExtractArgumentsScreen>{最终的GlobalKey< ScaffoldState>键=新的GlobalKey< ScaffoldState>();最后的便条= SnackBar(持续时间:持续时间(秒:5)，内容:Text("message" +'.'，textAlign:TextAlign.center)，backgroundColor:Colors.red [700]，);@override无效的initState(){super.initState();WidgetsBinding.instance.addPostFrameCallback((_){最终的路线Args1 =ModalRoute.of(context).settings.arguments as Map< String，String> ;;最终安装= routeArgs1 ['instalation'];最终消息= routeArgs1 ['message'];print('instalation $ {instalation}');print('message $ {message}');key.currentState.showSnackBar(SnackBar(content:Text(message)));});}@overridevoid didChangeDependencies(){super.didChangeDependencies();}@override窗口小部件build(BuildContext context){//从当前的ModalRoute设置中提取参数并进行强制转换//将它们作为ScreenArguments.最终路线Args =ModalRoute.of(context).settings.arguments as Map< String，String> ;;最终安装= routeArgs ['instalation'];最终消息= routeArgs ['message'];返回脚手架(键:键，appBar:AppBar(title:文字('$ {routeArgs ['code']}')，)，正文:列(子代:< Widget> [中心(子级:Text('instalation $ {instalation}')，)，加高按钮(onPressed:(){key.currentState.showSnackBar(snackBar);}，)，]，)，);}}//一个通过构造函数接受必要参数的Widget.PassArgumentsScreen类扩展了StatelessWidget {静态常量routeName ='/passArguments';最终的字符串标题；最终的字符串消息；//此小部件接受参数作为构造函数参数.它不是//从ModalRoute中提取参数.////参数是通过提供给//MaterialApp小部件.const PassArgumentsScreen({关键@需要this.title，@需要this.message，}):super(key:key);@override窗口小部件build(BuildContext context){返回脚手架(appBar:AppBar(标题:文字(标题)，)，身体:中心(子代:文字(消息)，)，);}}//您可以将任何对象传递给arguments参数.在这个例子中//创建一个同时包含可自定义标题和消息的类.类ScreenArguments {最终的字符串标题；最终的字符串消息；ScreenArguments(this.title，this.message);} I´m trying to send data with pushName. Then i try to get this data to show in a Toast message.
PushName
Navigator.pushNamed(
context,
'/navigator',
arguments: <String, String>{
'instalation': widget.instalation,
'message': DemoLocalizations.of(context)
.text('cancel-message') +
" " +
widget.datameterValue.toString(),
},
);
Trying to retrieve data
class Navigation extends StatefulWidget {
final ConnectionPage args;
Navigation({Key key, this.message, this.instalation, this.args}) : super(key: key);
}
class _NavigationState extends State<Navigation> {
void initState() {
super.initState();
print(widget.args); //NULL
final snackBar = SnackBar(
duration: Duration(seconds: 5),
content: Text(widget.args.messsage+ '.', textAlign: TextAlign.center),
backgroundColor: Colors.red[700],
);
key.currentState.showSnackBar(snackBar);
}
}
The problem: Return null.
So: What is the right way to get data using pushName? In the documentation show how can we get data inside Scaffold but i need to get data in the initState.
UPDATE
Routes
routes: {
'/login': (context) => LoginPage(),
'/navigator': (context) => Navigation(),
'/home': (context) => HomePageScreen(),
'/connect': (context) => ConnectionPage(),
},
UPDATE 2
I try something like this
Navigator.pushNamed(
context,
'/navigator',
arguments: Navigation(
instalation: widget.instalation,
message: DemoLocalizations.of(context)
.text('cancel-message') +
" " +
widget.datameterValue.toString(),
),
);
解决方案
To do this in initState You need WidgetsBinding.instance.addPostFrameCallback and ModalRoute.of(context).settings.arguments
Demo pass arguments: {'instalation': "123", "message": "456"}
You can see full code and working demo picture below
code snippet use push
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => ExtractArgumentsScreen(),
// Pass the arguments as part of the RouteSettings. The
// ExtractArgumentScreen reads the arguments from these
// settings.
settings: RouteSettings(
arguments: {'instalation': "123", "message": "456"},
),
),
);
@override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) {
final routeArgs1 =
ModalRoute.of(context).settings.arguments as Map<String, String>;
final instalation = routeArgs1['instalation'];
final message = routeArgs1['message'];
print('instalation ${instalation}');
print('message ${message}');
key.currentState
.showSnackBar(SnackBar(content: Text(message)));
});
}
code snippet use Navigator.pushNamed
return MaterialApp(
// Provide a function to handle named routes. Use this function to
// identify the named route being pushed, and create the correct
// Screen.
routes: {
'/extractArguments': (context) => ExtractArgumentsScreen(),
},
...
Navigator.pushNamed(
context,
ExtractArgumentsScreen.routeName,
arguments: {'instalation': "123", "message": "456"},
);
working demo
full code
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
// Provide a function to handle named routes. Use this function to
// identify the named route being pushed, and create the correct
// Screen.
routes: {
'/extractArguments': (context) => ExtractArgumentsScreen(),
},
onGenerateRoute: (settings) {
// If you push the PassArguments route
if (settings.name == PassArgumentsScreen.routeName) {
// Cast the arguments to the correct type: ScreenArguments.
final ScreenArguments args = settings.arguments;
// Then, extract the required data from the arguments and
// pass the data to the correct screen.
return MaterialPageRoute(
builder: (context) {
return PassArgumentsScreen(
title: args.title,
message: args.message,
);
},
);
}
},
title: 'Navigation with Arguments',
home: HomeScreen(),
);
}
}
class HomeScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Home Screen'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
// A button that navigates to a named route that. The named route
// extracts the arguments by itself.
RaisedButton(
child: Text("Navigate to screen that extracts arguments"),
onPressed: () {
// When the user taps the button, navigate to the specific route
// and provide the arguments as part of the RouteSettings.
Navigator.pushNamed(
context,
ExtractArgumentsScreen.routeName,
arguments: {'instalation': "123", "message": "456"},
);
/*Navigator.push(
context,
MaterialPageRoute(
builder: (context) => ExtractArgumentsScreen(),
// Pass the arguments as part of the RouteSettings. The
// ExtractArgumentScreen reads the arguments from these
// settings.
settings: RouteSettings(
arguments: {'instalation': "123", "message": "456"},
),
),
);*/
},
),
// A button that navigates to a named route. For this route, extract
// the arguments in the onGenerateRoute function and pass them
// to the screen.
RaisedButton(
child: Text("Navigate to a named that accepts arguments"),
onPressed: () {
// When the user taps the button, navigate to a named route
// and provide the arguments as an optional parameter.
Navigator.pushNamed(
context,
PassArgumentsScreen.routeName,
arguments: ScreenArguments(
'Accept Arguments Screen',
'This message is extracted in the onGenerateRoute function.',
),
);
},
),
],
),
),
);
}
}
// A Widget that extracts the necessary arguments from the ModalRoute.
class ExtractArgumentsScreen extends StatefulWidget {
static const routeName = '/extractArguments';
@override
_ExtractArgumentsScreenState createState() => _ExtractArgumentsScreenState();
}
class _ExtractArgumentsScreenState extends State<ExtractArgumentsScreen> {
final GlobalKey<ScaffoldState> key = new GlobalKey<ScaffoldState>();
final snackBar = SnackBar(
duration: Duration(seconds: 5),
content: Text("message" + '.', textAlign: TextAlign.center),
backgroundColor: Colors.red[700],
);
@override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) {
final routeArgs1 =
ModalRoute.of(context).settings.arguments as Map<String, String>;
final instalation = routeArgs1['instalation'];
final message = routeArgs1['message'];
print('instalation ${instalation}');
print('message ${message}');
key.currentState
.showSnackBar(SnackBar(content: Text(message)));
});
}
@override
void didChangeDependencies() {
super.didChangeDependencies();
}
@override
Widget build(BuildContext context) {
// Extract the arguments from the current ModalRoute settings and cast
// them as ScreenArguments.
final routeArgs =
ModalRoute.of(context).settings.arguments as Map<String, String>;
final instalation = routeArgs['instalation'];
final message = routeArgs['message'];
return Scaffold(
key: key,
appBar: AppBar(
title: Text(' ${routeArgs['code']} '),
),
body: Column(
children: <Widget>[
Center(
child: Text('instalation ${instalation}'),
),
RaisedButton(
onPressed: () {
key.currentState.showSnackBar(snackBar);
},
),
],
),
);
}
}
// A Widget that accepts the necessary arguments via the constructor.
class PassArgumentsScreen extends StatelessWidget {
static const routeName = '/passArguments';
final String title;
final String message;
// This Widget accepts the arguments as constructor parameters. It does not
// extract the arguments from the ModalRoute.
//
// The arguments are extracted by the onGenerateRoute function provided to the
// MaterialApp widget.
const PassArgumentsScreen({
Key key,
@required this.title,
@required this.message,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
body: Center(
child: Text(message),
),
);
}
}
// You can pass any object to the arguments parameter. In this example,
// create a class that contains both a customizable title and message.
class ScreenArguments {
final String title;
final String message;
ScreenArguments(this.title, this.message);
}
这篇关于Flutter-使用pushName获取数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
查看全文
