Calling method in main/App class in Flutter? - flutter

Question

I need to call from another widget the App class. How can I get a reference to the app class? I tried something like this:
static App myApp = this;
but a "this" is not defined, nor a "self".
Is there a way to make a "App" variable or put the app object into some kind of global variable?
EDIT:
To be more clear: I use a tabbed navigation style app and want to display a fullscreen spinning indicator (ModalProgressHud) that something is loading from the backend.
Now when I add the spinner code to some of the screens, the tabs will still be visible and clickable when the spinner is shown. Hence the idea to move the spinner code to the main app file, surrounding the tabbar creation.
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'My cool app',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: new App(),
);
}
}
Now in the App class, I initiate the tabs like this and wrap them in the build function inside the spinning indicators call ("ModalProgressHud"):
body: ModalProgressHUD(child: buildTabs(context), inAsyncCall: _saving, color: Colors.grey, opacity: 0.5),
import 'package:modal_progress_hud/modal_progress_hud.dart';
class App extends StatefulWidget {
#override
State<StatefulWidget> createState() => AppState();
}
class AppState extends State<App> {
bool _saving = false;
TabItem currentTab = TabItem.Dashboard;
Map<TabItem, GlobalKey<NavigatorState>> navigatorKeys = {
TabItem.Dashboard: GlobalKey<NavigatorState>(),
TabItem.Family: GlobalKey<NavigatorState>(),
TabItem.Groups: GlobalKey<NavigatorState>(),
TabItem.ShoppingList: GlobalKey<NavigatorState>(),
TabItem.Me: GlobalKey<NavigatorState>(),
};
AppState() {
_initManagers();
}
void _initManagers() {
new BackendManager();
new ShoppingListManager();
new UserManager();
}
void _selectTab(TabItem tabItem) {
UserManager user = new UserManager();
if (user.userIsLoggedIn()) {
// only if user is logged-in we allow to switch bottom navi tabs
setState(() {
currentTab = tabItem;
});
}
}
#override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () async =>
!await navigatorKeys[currentTab].currentState.maybePop(),
child: Scaffold(
resizeToAvoidBottomPadding: false,
resizeToAvoidBottomInset: false,
// HERE THE WRAP OF THE MAIN TABS IN THE HUD WIDGET
body: ModalProgressHUD(child: buildTabs(context), inAsyncCall: _saving, color: Colors.grey, opacity: 0.5),
bottomNavigationBar: BottomNavigation(
currentTab: currentTab,
onSelectTab: _selectTab,
),
),
);
}
Widget buildTabs(BuildContext context) {
return Stack(children: <Widget>[
_buildOffstageNavigator(TabItem.Dashboard),
_buildOffstageNavigator(TabItem.Search),
_buildOffstageNavigator(TabItem.Shop),
_buildOffstageNavigator(TabItem.ShoppingList),
_buildOffstageNavigator(TabItem.Me),
]);
}
Widget _buildOffstageNavigator(TabItem tabItem) {
return Offstage(
offstage: currentTab != tabItem,
child: TabNavigator(
navigatorKey: navigatorKeys[tabItem],
tabItem: tabItem,
),
);
}
void _submit() {
setState(() {
_saving = true;
});
//Simulate a service call
print('>>>>>> submitting to backend...');
new Future.delayed(new Duration(seconds: 4), () {
setState(() {
_saving = false;
});
});
}
}
The ModalProgressHud is now in the app class. My problem is now, I want to set / call the ModalProgressHud from any other widget to show the fullscreen overlay spinning indicator.
Hence I was thinking if a global static variable works (and how do I set this?) or if there is any other way to call the submit() function inside the App class.

Answer 1

First, I wonder why you need to pass the reference of the app class?
If you want to pass the app instance or reference it to the child widget, you can create a widget class with a constructor accepting the App object.
NOTE: If you need this because you have to pass on some data, you might consider using provider or inheritedWidget + BloC.
This is just a rough example, if you can provide more details that might actually help, please do.
AnotherWidget.dart
class AnotherWidget extends StatelessWidget {
final MyApp myApp;
const AnotherWidget({Key key, this.myApp}) : super(key: key);
// Do whatever you want with myApp instance
}
MyApp.dart
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'AnotherWidgetDemo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: AnotherWidget(myApp: this),
);
}
}
Hope this helps.

Answer 2

Try something like they do in Flutter for Web, import the file and use as, then you have the reference for calling a method
import 'package:hello_web/main.dart' as app;
main() async {
app.main();
}