How to make the activity stack null in flutter? - flutter

Question

I have 4 walkthrough screens, on reaching the ending of the screens when i go to the homepage of my app which is named as TestScreen here,when i press the back button in my phone i again go back to the walkthrough pages which i dont want and it throws an exception too ("Failed assertion: line 1554 pos 12: '!_debugLocked': is not true."). So i was thinking if i make the activity stack null after coming to TestScreen it might work but i am not able to do so. Please help me.
Main.dart
library flutter_walkthrough;
import 'package:flutter/material.dart';
import 'package:comp_apps/walkthrough.dart';
void main(){
runApp(MyApp());
}
class MyApp extends StatelessWidget {
final List<Walkthrough> list = [
Walkthrough(
title: "Title 1",
content: "Content 1",
imageIcon: Icons.restaurant_menu,
),
Walkthrough(
title: "Title 2",
content: "Content 2",
imageIcon: Icons.search,
),
Walkthrough(
title: "Title 3",
content: "Content 3",
imageIcon: Icons.shopping_cart,
),
Walkthrough(
title: "Title 4",
content: "Content 4",
imageIcon: Icons.verified_user,
),
];
#override
Widget build(BuildContext context) {
return MaterialApp(
home: IntroScreen(list, MaterialPageRoute(builder: (context)=>
TestScreen())).,
);
}
}
class TestScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Hello"),
automaticallyImplyLeading: false,
),
);
}
}
class IntroScreen extends StatefulWidget {
final List<Walkthrough> walkthroughList;
final MaterialPageRoute pageRoute;
IntroScreen(this.walkthroughList, this.pageRoute);
void skipPage(BuildContext context) {
Navigator.push(context, pageRoute);
}
#override
_IntroScreenState createState() => _IntroScreenState();
}
class _IntroScreenState extends State<IntroScreen> {
final PageController controller = new PageController();
int currentPage = 0;
bool lastPage = false;
void _onPageChanged(int page) {
setState(() {
currentPage = page;
if (currentPage == widget.walkthroughList.length - 1) {
lastPage = true;
} else {
lastPage = false;
}
});
}
#override
Widget build(BuildContext context) {
return Container(
color: Color(0xFFEEEEEE),
padding: const EdgeInsets.all(10.0),
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Expanded(
child: Container(),
flex: 1,
),
Expanded(
flex: 3,
child: PageView(
children: widget.walkthroughList,
controller: controller,
onPageChanged: _onPageChanged,
),
),
Expanded(
flex: 1,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
FlatButton(
child: Text(
lastPage ? "" : "SKIP",
style: TextStyle(
color: Colors.black,
fontWeight: FontWeight.bold,
fontSize: 16.0),
),
onPressed: () => lastPage ? null : widget.skipPage(context),
),
FlatButton(
child: Text(
lastPage ? "GOT IT" : "NEXT",
style: TextStyle(
color: Colors.black,
fontWeight: FontWeight.bold,
fontSize: 16.0,
),
),
onPressed: () => lastPage
? widget.skipPage(context)
: controller.nextPage(
duration: Duration(milliseconds: 300),
curve: Curves.easeIn),
)
],
),
)
],
),
);
}
}
Walkthrough.dart
import 'package:flutter/material.dart';
class Walkthrough extends StatefulWidget {
final title;
final content;
final imageIcon;
final imagecolor;
Walkthrough({this.title, this.content, this.imagecolor, this.imageIcon});
#override
_WalkthroughState createState() => _WalkthroughState();
}
class _WalkthroughState extends State<Walkthrough>
with SingleTickerProviderStateMixin {
Animation animation;
AnimationController animationController;
#override
void initState() {
// TODO: implement initState
super.initState();
animationController = AnimationController(vsync: this,duration:
Duration(milliseconds: 500));
animation = Tween(
begin: -250.0, end: 0.0).animate(CurvedAnimation(parent:
animationController, curve: Curves.easeInOut));
animation.addListener(() => setState(() {}));
animationController.forward();
}
#override
void dispose() {
// TODO: implement dispose
super.dispose();
animationController.dispose();
}
#override
Widget build(BuildContext context) {
return Container(
padding: const EdgeInsets.all(20.0),
child: Material(
animationDuration: Duration(milliseconds: 500),
elevation: 2.0,
borderRadius: BorderRadius.all(Radius.circular(5.0)),
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Transform(
transform: Matrix4.translationValues(animation.value, 0.0, 0.0),
child: Text(widget.title,style: TextStyle(
fontSize: 20.0,
fontWeight: FontWeight.bold,
color: Colors.black
),),
),
Transform(
transform: Matrix4.translationValues(animation.value, 0.0, 0.0),
child: Text(widget.content,
softWrap: true,
textAlign: TextAlign.center,
style: TextStyle(
fontWeight: FontWeight.normal,
fontSize: 15.0,
color: Colors.black,
),),
),
Icon(
widget.imageIcon,
size: 100.0,
color: widget.imagecolor,
)
],
),
),
);
}
}