Flutter : sending data across multiple screens - flutter

Question

I have 3 Widget MyApp Widget ,Home Widget, and Sliver Appbar Widget, It's connected to each other. Example MyApp Widget -> Home Widget -> SliverAppbar Widget.
My question is , how to Passing data from My App Widget directly to SliverAppBar Widget ?
I found what i think it's can solve my case that is Inherited Widget. But i confused to understading to use this widget.
I already try using Inherited Widget as documentation like this :
MyApp Widget
class SettingsApp extends InheritedWidget {
SettingsApp({Key key, this.isDarkMode = false, Widget child})
: super(key: key, child: child);
final bool isDarkMode;
static SettingsApp of(BuildContext context) {
return (context.dependOnInheritedWidgetOfExactType<SettingsApp>());
}
#override
bool updateShouldNotify(SettingsApp oldWidget) {
return true;
}
}
SliverAppBar Widget
class SliverAppBarCustom extends StatelessWidget {
final Box detbBox = Hive.box("debt_box");
final UserModelHive userModelHive = Hive.box("user_box").get("userSession");
#override
Widget build(BuildContext context) {
final isDarkMode =
context.dependOnInheritedWidgetOfExactType<SettingsApp>().isDarkMode;
print(isDarkMode.toString());
var mediaQuery = MediaQuery.of(context);
var textTheme = Theme.of(context).textTheme;
return Text(isDarkMode.toString());
}
}
But i get this error :
Log
The following NoSuchMethodError was thrown building SliverAppBarCustom(dirty):
The getter 'isDarkMode' was called on null.
Receiver: null
Tried calling: isDarkMode

Answer 1

Using ScopedModel
import 'package:flutter/material.dart';
import 'package:scoped_model/scoped_model.dart';
void main() => runApp(MyApp());
class SettingsModel extends Model {
bool _isDarkMode;
SettingsModel({bool isDarkMode}) : _isDarkMode = isDarkMode ?? false;
bool get isDarkModel => _isDarkMode;
set isDarkModel(bool value) {
_isDarkMode = value;
notifyListeners();
}
void switchTheme() {
_isDarkMode = !_isDarkMode;
notifyListeners();
}
static SettingsModel of(BuildContext context) {
return ScopedModel.of<SettingsModel>(context);
}
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return ScopedModel<SettingsModel>(
model: SettingsModel(isDarkMode: true),
child: MaterialApp(
home: InitPage(),
),
);
}
}
class InitPage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text("Init Page")),
body: SizedBox.expand(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
ScopedModelDescendant<SettingsModel>(
builder: (context, child, model) {
return Text('Is Dark Mode: ${model.isDarkModel}');
},
),
RaisedButton(
child: Text("Next Page"),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => SecondPage(),
),
);
},
),
],
),
),
);
}
}
class SecondPage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Second Page"),
),
body: SizedBox.expand(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
ScopedModelDescendant<SettingsModel>(
builder: (context, child, model) {
return Text('Is Dark Mode: ${model.isDarkModel}');
},
),
RaisedButton(
child: Text("Switch Theme"),
onPressed: SettingsModel.of(context).switchTheme,
),
],
),
),
);
}
}
Important: You should not change _isDarkModel without notifyListeners(). If you do UI may not update.