How to call setState in a widget to change that widget with other one? - flutter

Question

I have 2 widget and I put the first one into a variable. When I click a button in the first widget, I will call setState and put the second widget to the variable to rebuild. However, it didn't work.
I try to call setState in the parent widget of them and it work. Anyone know what wrong with it and how to solve this?
This is my code:
Widget checkinWidget = CheckInTemplate();
Column(
children: <Widget>[
Expanded(
flex: 3,
child: Container(),
),
Expanded(
flex: 1,
child: AnimatedSwitcher(
duration: const Duration(seconds: 1),
child: checkinWidget
),
)
],
),
I put the first widget CheckInTemplate to a variable and in CheckInTemplate, I have a button:
RaisedButton(
padding: EdgeInsets.symmetric(vertical: 15.0, horizontal: 60),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(30.0)
),
color: Colors.white,
onPressed: (){
setState(() {
checkinWidget = CaptureCameraTemplate();
});
},
child: Text('Check in',
style: TextStyle(
fontSize: 25,
fontFamily: 'FredokaOne'
),),
),
When I click the button, nothing happen.

Answer 1

I developed one example for this, kindly check the below code
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: WidgetHandling(),
);
}
}
class WidgetHandling extends StatefulWidget {
#override
State<StatefulWidget> createState() {
return _WidgetHandling();
}
}
class _WidgetHandling extends State<WidgetHandling> {
Widget widgetHolder;
void initState() {
widgetHolder = firstWidget();
super.initState();
}
Widget firstWidget() {
return Container(
color: Colors.white,
child: Center(
child: FlatButton(
color: Colors.blue,
textColor: Colors.white,
padding: EdgeInsets.all(8.0),
splashColor: Colors.blueAccent,
onPressed: () {
setState(() {
widgetHolder = secondWidget();
});
},
child: Text(
"First Widget",
style: TextStyle(fontSize: 20.0),
),
),
),
);
}
Widget secondWidget() {
return Container(
color: Colors.grey,
child: Center(
child: FlatButton(
color: Colors.blue,
textColor: Colors.white,
padding: EdgeInsets.all(8.0),
splashColor: Colors.blueAccent,
onPressed: () {
setState(() {
widgetHolder = firstWidget();
});
},
child: Text(
"Second Widget",
style: TextStyle(fontSize: 20.0),
),
),
),
);
}
#override
Widget build(BuildContext context) {
return widgetHolder;
}
}

Answer 2

You might have added this line,
Widget checkinWidget = CheckInTemplate();
in build method.
Remove it from build method and put to out side of build and then it will work.