Flutter - Get data using pushName - flutter

Question

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(),
),
);

Answer 1

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);
}

Answer 2

So, I see you're using the simple routes approach.
In order to extract route arguments you need to supply an onGenerateRoute function to your MaterialApp (or Cupertino, I guess).
You can find an exhaustive example on how to do it here, so I won't crowd this answer more than that.
Hope this solves your problem, happy coding!