Flutter pass data to new screen with onTap - flutter

Question

My application has a bottom navigation bar, with 2 pages in the menu.
On page 1, I can fill out a form and it calculates me values ​​that it displays to me by pushing in a 1.1 page.
On this page I have a button that allows me to redirect me to page 2 as if I clicked menu 2 of the navigation bar.
This works. My problem is how to send the data from my page 1.1 to this page 2.
The goal being that my page 2 is a form which is empty if I call it by the navigation bar but which is filled automatically if I pass by the page 1.1 in focus of the calculated values.
Here an exemple of the redirection that I do:
Here is my code :
my_app.dart :
final ThemeData _AppTheme = AppTheme().data;
final navBarGlobalKey = GlobalKey(); // => This is my key for redirect page
class MyApp extends StatefulWidget{
#override
State<StatefulWidget> createState() => MyAppState();
}
class MyAppState extends State<MyApp>{
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'App',
home: MyBottomNavigationBar(),
theme: _AppTheme,
navigatorKey: locator<NavigationService>().navigatorKey,
onGenerateRoute: Router.generateRoute,
initialRoute: HOME_ROUTE,
);
}
}
My bottom_navigation_bar.dart :
class MyBottomNavigationBar extends StatefulWidget
{
MyBottomNavigationBar({Key key}) : super(key: key);
#override
_MyBottomNavigationBarState createState() => _MyBottomNavigationBarState();
}
class _MyBottomNavigationBarState extends State<MyBottomNavigationBar>
{
int _pageIndex = 0;
final List<Widget> _pagesOption = [
page1.1(), // => Here I load direclty my page 1.1 with data for the exemple
page2(),
];
void onTappedBar(int index)
{
setState(() {
_pageIndex = index;
});
}
#override
Widget build(BuildContext context) {
return SafeArea(
child : Scaffold(
body : _pagesOption.elementAt(_pageIndex),
bottomNavigationBar: BottomNavigationBar(
key: navBarGlobalKey,
currentIndex: _pageIndex,
onTap: onTappedBar,
type: BottomNavigationBarType.fixed,
items : [
BottomNavigationBarItem(
icon : Icon(Icons.home),
title : Text('Home')
),
BottomNavigationBarItem(
icon : Icon(Icons.settings),
title : Text('Setting')
),
]
),
)
);
}
}
And here my widget submit button of page 1.1 :
Widget _getSubmitButton(){
return RaisedButton(
child: Text(
'Send'
),
onPressed: () {
final BottomNavigationBar navigationBar = navBarGlobalKey.currentWidget;
navigationBar.onTap(1); // => How to send data that I have in my page ???
},
);
}

Answer 1

For this, you can use Shared Preferences, the main idea is that:
Store the value of the calculated value in SharedPref from Page 1 when you're passing to Page 1.1
Let you checks for the value by default in Page 2's initState(), any changes in the Shared Preferences will be fetched in the Page 2 itself, using SharedPref get method.
WHY?
This is probably a cleaner way to achieve what you want, since in the BottomNavigationBar will not help you do this, but a Shared Preferences value will always give you that data which you can use it any time
Let's see how you can achieve this:
PAGE ONE
// Set the data of the form here
class _PageOneState extends State<PageOne>
{
void onSubmit() async{
SharedPreferences prefs = await SharedPreferences.getInstance();
//make sure you store the calculated value, if that is String
// use setString() or if it is an int, setInt()
// and then pass it to the SharedPref
// key is a string name, which is used to access
// key and store, so choose the name wisely
await prefs.setInt("key", your_calculated_value);
}
}
PAGE TWO
class _PageTwoState extends State<PageTwo>
{
Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
// This will be responsible for getting the result from SharedPref
int calculated_value;
#override
void initState(){
super.initState();
// get your list here
calculated_value = _prefs.then((SharedPreferences prefs){
// here if no data is then _values will have 0
// which you can use it to check and populate data
return (prefs.getInt("key") ?? 0);
});
}
}
This is the most reasonable way of doing the thing which you want. In this manner, whenever, PageTwo will trace any values, it will reflect, else, your choice for 0 check result. Let me know, if you have any doubts in that.

Answer 2

In your FirstActivity
onPressed: () {
navigatePush(SecondActivity(text: "Data"));
}
In your SecondActivity
class SecondActivity extends StatefulWidget {
String text;
SecondActivity({this.text});
}

Answer 3

You can pass the the values as arguments when you push to your new screen. This could get messy if you're building a larger project.
A cleaner implementation would be to use a Provider. Set up the data you want in a model mixed in with ChangeNotifier and use Provider.of<*name of your class*>(context) where ever you need to use it.