Related
I created a page where I can add exercise for my classes and in this page students can create their custom training (it's a gym app), the only problem is that every time the user closes the app all the training is gone.
I leave below my code, I've done some researches and I kind of understood that there is something with SharPreferences but all the tutorial talk about a login page which is not my case.
can you please advise?? I leave my code below, thanks!
import 'package:flutter/material.dart';
import 'package:flutter_slidable/flutter_slidable.dart';
class Custom extends StatefulWidget {
#override
_CustomState createState() => new _CustomState();
}
class _CustomState extends State<Custom> {
int _count = 0;
#override
Widget build(BuildContext context) {
List<Widget> _esercizi = List.generate(_count, (int i) => Esercizi());
bool visible = _count > 0;
return GestureDetector(
onTap: () {
FocusScope.of(context).requestFocus(FocusNode());
},
child: Scaffold(
appBar: AppBar(
title: Text('Scheda personalizzata'),
actions: [
Visibility(
visible: visible,
child: IconButton(
icon: Icon(Icons.remove_rounded),
onPressed: _removeNewEsercizi,
),
),
IconButton(icon: Icon(Icons.add), onPressed: _addNewEsercizi),
],
backgroundColor: Colors.blueGrey,
),
body: LayoutBuilder(builder: (context, constraint) {
return Padding(
padding: const EdgeInsets.all(10.0),
child: SingleChildScrollView(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Container(
height: 700,
child: ListView(
scrollDirection: Axis.vertical,
children: _esercizi,
),
),
//new ContactRow()
],
),
),
);
}),
),
);
}
void _addNewEsercizi() {
setState(() {
_count = _count + 1;
});
}
void _removeNewEsercizi() {
setState(() {
_count = _count - 1;
});
}
}
class Esercizi extends StatefulWidget {
#override
State<StatefulWidget> createState() => _Esercizi();
}
class _Esercizi extends State<Esercizi> {
String dropdownValue = 'Seleziona esercizio';
#override
Widget build(BuildContext context) {
Size size = MediaQuery.of(context).size;
return Padding(
padding: const EdgeInsets.all(2.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
DropdownButton<String>(
value: dropdownValue,
style: TextStyle(color: Colors.blueGrey),
onChanged: (String newValue) {
setState(() {
dropdownValue = newValue;
});
},
items: <String>['Seleziona esercizio', 'One', 'Two', 'Three', 'Fo'
'ur', 'Five', 'Six']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
),
Container(
height: 50,
width: 90,
child: Center(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: TextField(
cursorColor: Colors.white,
decoration: InputDecoration(
hintText: 'Time/Reps',
hintStyle: TextStyle(color: Colors.blueGrey),
),
keyboardType: TextInputType.number,
),
),
),
),
],
),
);
}
}
My Scrollview not Responding, can someone tell what I am missing in code:
Please Suggest me how to add scroll view listener I'm beginner.
import 'package:flutter/material.dart';
import 'package:share/share.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:url_launcher/url_launcher.dart';
import '../main.dart';
import 'favourite_articles.dart';
import 'coin_system.dart';
class Settings extends StatefulWidget {
#override
_SettingsState createState() => _SettingsState();
}
class _SettingsState extends State<Settings> {
bool _notification = false;
ScrollController _controller;
#override
void initState() {
super.initState();
checkNotificationSetting();
}
checkNotificationSetting() async {
final prefs = await SharedPreferences.getInstance();
final key = 'notification';
final value = prefs.getInt(key) ?? 0;
if (value == 0) {
setState(() {
_notification = false;
});
} else {
setState(() {
_notification = true;
});
}
}
saveNotificationSetting(bool val) async {
final prefs = await SharedPreferences.getInstance();
final key = 'notification';
final value = val ? 1 : 0;
prefs.setInt(key, value);
if (value == 1) {
setState(() {
_notification = true;
});
} else {
setState(() {
_notification = false;
});
}
Future.delayed(const Duration(milliseconds: 500), () {
Navigator.of(context).pushReplacement(
MaterialPageRoute(builder: (BuildContext context) => MyHomePage()));
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
appBar: AppBar(
centerTitle: true,
title: Text(
'More',
style: TextStyle(
color: Colors.black,
fontWeight: FontWeight.bold,
fontSize: 20,
fontFamily: 'Poppins'),
),
elevation: 5,
backgroundColor: Colors.white,
actions: <Widget>[
IconButton(
icon: Icon(Icons.mail),
color: Colors.black,
tooltip: 'Song Request',
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CoinSystem(),
),
);
})
],
),
body: Container(
decoration: BoxDecoration(color: Colors.white),
child: SingleChildScrollView(
controller: _controller,
scrollDirection: Axis.vertical,
child: Column(
children: <Widget>[
Container(
alignment: Alignment.center,
padding: EdgeInsets.fromLTRB(0, 20, 0, 10),
child: Image(
image: AssetImage('assets/icon.png'),
height: 50,
),
),
Container(
alignment: Alignment.center,
padding: EdgeInsets.fromLTRB(0, 10, 0, 20),
child: Text(
"Version 2.1.0 \n ",
textAlign: TextAlign.center,
style: TextStyle(height: 1.6, color: Colors.black87),
),
),
Divider(
height: 10,
thickness: 2,
),
//ListWheelScrollView(
ListView(
//itemExtent: 75,
shrinkWrap: true,
children: <Widget>[
InkWell(
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => FavouriteArticles(),
),
);
},
child: ListTile(
leading: Image.asset(
"assets/more/favourite.png",
width: 30,
),
title: Text('Favourite'),
subtitle: Text("See the saved songs"),
),
),
//Song Request Code
InkWell(
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CoinSystem(),
),
);
},
child: ListTile(
leading: Image.asset(
"assets/more/songrequest.png",
width: 30,
),
title: Text('Songs Request'),
subtitle: Text("Request your favourite songs"),
),
),
//Song Request Code End
ListTile(
leading: Image.asset(
"assets/more/notification.png",
width: 30,
),
isThreeLine: true,
title: Text('Notification'),
subtitle: Text("Change notification preference"),
trailing: Switch(
onChanged: (val) async {
await saveNotificationSetting(val);
},
value: _notification),
),
],
)
],
),
),
),
//),
);
//);
}
}
So, I have tried SingleChildScrollView, in that I have Container and Listview. But Listview doesn't response on scrolling action in landscape mode.
I have added ScrollController _controller; Do i have to create _controller class that listern the scrolling action?
In my understanding, you want to be able to get 2 scrolling. 1. using SingleChildScrollView and inside that Widget, you want to be able to scroll the bottom layer, thus you use ListView. To make it work, you have to place your ListView inside widget that has certain height. Example this implementation is:
SingleChildScrollView(
scrollDirection: Axis.vertical,
child: Column(
children: <Widget>[
SizedBox(child: Text('Upper scrollable'), height: 450),
Divider(
height: 10,
thickness: 2,
),
Container(
height: 350,
child: ListView(
shrinkWrap: true,
children: <Widget>[
Container(
color:Colors.red,
child: SizedBox(child: Text('Bottom scrollable'), height: 450),
),
],
),
)
],
),
),
If you don't want to use 2 scroll, don't use ListView inside SingleChildScrollView.
ListView cannot be wrapped with SingleChildScrollView remove it
surround ListView with Expanded Widget
try one of the two alternatives.
I need now to setState for a MaterialButton for a bottomNavigationBar to change a widget which was a part of the screen...
So the problem related for the below part:
MaterialButton(
padding: EdgeInsets.all(0),
minWidth: 155,
onPressed: () {
setState(() {
currentScreen =
HomeGrid(); // if user taps on this dashboard tab will be active
currentTab = 0;
});
},
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Icon(
Icons.home,
color: currentTab == 0
? Colors.blue
: Colors.grey,
),
Text(
'Home',
style: TextStyle(
color: currentTab == 0
? Colors.blue
: Colors.grey,
),
),
],
),
),
and this is the full code:
import 'package:flutter/rendering.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../providers/properties.dart';
import '../providers/cities.dart';
import '../widgets/home_grid.dart';
import '../widgets/properties_grid.dart';
import '../app_theme.dart';
class MyHomePage extends StatefulWidget {
const MyHomePage({Key key}) : super(key: key);
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
int currentTab = 0;
ScrollController _scrollController = ScrollController();
bool _showBottomBar = true;
final List<Widget> screens = [
HomeGrid(),
PropertiesGrid(),
];
Widget currentScreen = HomeGrid();
int _selectedPageIndex = 0;
_scrollListener() {
if (_scrollController.position.userScrollDirection ==
ScrollDirection.reverse) {
setState(() {
_showBottomBar = false;
});
} else if (_scrollController.position.userScrollDirection ==
ScrollDirection.forward) {
setState(() {
_showBottomBar = true;
});
}
}
AnimationController animationController;
bool multiple = true;
#override
void initState() {
animationController = AnimationController(
duration: const Duration(milliseconds: 2000), vsync: this);
_scrollController.addListener(_scrollListener);
super.initState();
}
void _selectPage(int index) {
setState(() {
_selectedPageIndex = index;
});
}
Future<bool> getData() async {
await Future<dynamic>.delayed(const Duration(milliseconds: 0));
return true;
}
#override
void dispose() {
animationController.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
// final properties = Provider.of<Properties>(context, listen: false);
return DefaultTabController(
length: 6, // Added
initialIndex: 0,
child: Scaffold(
resizeToAvoidBottomPadding: false,
extendBody: true,
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () {},
),
floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
bottomNavigationBar: AnimatedContainer(
duration: Duration(milliseconds: 500),
child: _showBottomBar
? BottomAppBar(
elevation: 0,
shape: CircularNotchedRectangle(),
notchMargin: 10,
child: Container(
height: 60,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
MaterialButton(
padding: EdgeInsets.all(0),
minWidth: 155,
onPressed: () {
setState(() {
currentScreen =
HomeGrid(); // if user taps on this dashboard tab will be active
currentTab = 0;
});
},
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Icon(
Icons.home,
color: currentTab == 0
? Colors.blue
: Colors.grey,
),
Text(
'Home',
style: TextStyle(
color: currentTab == 0
? Colors.blue
: Colors.grey,
),
),
],
),
),
],
),
// Right Tab bar icons
Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
MaterialButton(
padding: EdgeInsets.all(0),
minWidth: 60,
onPressed: () {
setState(() {
currentScreen =
PropertiesGrid(); // if user taps on this dashboard tab will be active
currentTab = 1;
});
},
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Icon(
Icons.view_list,
color: currentTab == 1
? Colors.blue
: Colors.grey,
),
Text(
'Property List',
style: TextStyle(
color: currentTab == 1
? Colors.blue
: Colors.grey,
),
),
],
),
),
MaterialButton(
padding: EdgeInsets.all(0),
minWidth: 77,
onPressed: () {
setState(() {
// currentScreen =
// Settings(); // if user taps on this dashboard tab will be active
currentTab = 2;
});
},
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Icon(
Icons.location_searching,
color: currentTab == 2
? Colors.blue
: Colors.grey,
),
Text(
'Map',
style: TextStyle(
color: currentTab == 2
? Colors.blue
: Colors.grey,
),
),
],
),
),
],
)
],
),
),
)
: Container(
color: Colors.white,
width: MediaQuery.of(context).size.width,
),
),
backgroundColor: AppTheme.white,
body: Stack(
children: <Widget>[
FutureBuilder<bool>(
future: getData(),
builder: (BuildContext context, AsyncSnapshot<bool> snapshot) {
if (!snapshot.hasData) {
return const SizedBox();
} else {
return Padding(
padding: EdgeInsets.only(
top: MediaQuery.of(context).padding.top),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
appBar(),
tabBar(),
Expanded(
child: FutureBuilder<bool>(
future: getData(),
builder: (BuildContext context,
AsyncSnapshot<bool> snapshot) {
if (!snapshot.hasData) {
return const SizedBox();
} else {
return MultiProvider(
providers: [
ChangeNotifierProvider(
create: (context) => Properties()),
ChangeNotifierProvider(
create: (context) => Cities()),
], child: HomeGrid(),
);
}
},
),
),
],
),
);
}
},
),
],
),
),
);
}
Widget appBar() {
return SizedBox(
height: AppBar().preferredSize.height,
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 8, left: 8),
child: Container(
width: AppBar().preferredSize.height - 8,
height: AppBar().preferredSize.height - 8,
),
),
Expanded(
child: Center(
child: Padding(
padding: const EdgeInsets.only(top: 4),
child:
Image.asset('assets/images/logo.png', fit: BoxFit.contain),
),
),
),
Padding(
padding: const EdgeInsets.only(top: 8, right: 8),
child: Container(
width: AppBar().preferredSize.height - 8,
height: AppBar().preferredSize.height - 8,
color: Colors.white,
child: Material(
color: Colors.transparent,
child: InkWell(
borderRadius:
BorderRadius.circular(AppBar().preferredSize.height),
child: Icon(
Icons.location_on,
color: AppTheme.dark_grey,
),
onTap: () {
setState(() {
multiple = !multiple;
});
},
),
),
),
),
],
),
);
}
Widget tabBar() {
return SizedBox(
height: AppBar().preferredSize.height,
child: TabBar(
isScrollable: true,
unselectedLabelColor: Colors.green,
labelColor: Colors.blue,
indicatorColor: Colors.blue,
labelStyle: TextStyle(fontSize: 15.0, fontStyle: FontStyle.italic),
tabs: [
Tab(
child: Text('All'),
),
Tab(
child: Text('Office'),
),
Tab(
child: Text('Commercial'),
),
Tab(
child: Text('Land'),
),
Tab(
child: Text('House/Villa'),
),
Tab(
child: Text('Apartement'),
),
],
),
);
}
}
To be clear I need when Click on Home Icon and set also the default for the home widget just set state for the HomeGrid, and when click on Properties List just set the state and show the Properties Grid
if there's any needed info please follow up the below question:
How to replace a small widget for a child when onPressed on a BottomAppBar Icon Item
I hope this would be Clear enough...
Added
I think there's still missing somthing to do in the below part:
Expanded(
child: FutureBuilder<bool>(
future: getData(),
builder: (BuildContext context,
AsyncSnapshot<bool> snapshot) {
if (!snapshot.hasData) {
return const SizedBox();
} else {
return MultiProvider(
providers: [
ChangeNotifierProvider(
create: (context) => Properties()),
ChangeNotifierProvider(
create: (context) => Cities()),
],
// child: HomeGrid(_showOnlyFavorites),
child: HomeGrid(),
);
}
},
),
),
Well I Solved it So related to the previous Code is working fine the the problem in the below line:
child: HomeGrid(),
changed to this:
child: currentScreen,
I have to put the child as the currentScreen related to this line:
Widget currentScreen = HomeGrid();
as to be the final Epanded widget to be as the below code:
Expanded(
child: FutureBuilder<bool>(
future: getData(),
builder: (BuildContext context,
AsyncSnapshot<bool> snapshot) {
if (!snapshot.hasData) {
return const SizedBox();
} else {
return MultiProvider(
providers: [
ChangeNotifierProvider(
create: (context) => Properties()),
ChangeNotifierProvider(
create: (context) => Cities()),
],
// child: HomeGrid(_showOnlyFavorites),
child: currentScreen,
);
}
},
),
),
I am creating an multiple choice quiz app using flutter, currently when user selects an answer in radio list tile it, will check for correct answer and show a toast message.
Need to update the code to highlight selected answer with green color if answer is correct
and red if the answer is wrong.
If any idea please update the code and share the code. Thanks in advance.
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:mechanicalaptitude/quiz/models/category.dart';
import 'package:mechanicalaptitude/quiz/models/question.dart';
import 'package:mechanicalaptitude/quiz/ui/pages/quiz_finished.dart';
import 'package:html_unescape/html_unescape.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:admob_flutter/admob_flutter.dart';
class QuizPage extends StatefulWidget {
final List<Question> questions;
final Category category;
const QuizPage({Key key, #required this.questions, this.category})
: super(key: key);
#override
_QuizPageState createState() => _QuizPageState();
}
class _QuizPageState extends State<QuizPage> {
final TextStyle _questionStyle = TextStyle(
fontSize: 18.0, //font size of the questions
fontWeight: FontWeight.bold,
color: Colors.red);
int _currentIndex = 0;
int i = 0;
int hint_index = 0;
var option1;
final Map<int, dynamic> _answers = {};
final GlobalKey<ScaffoldState> _key = GlobalKey<ScaffoldState>();
#override
Widget build(BuildContext context) {
Question question = widget.questions[_currentIndex];
final List<dynamic> options = question.incorrectAnswers;
if (!options.contains(question.correctAnswer)) {
options.add(question.correctAnswer);
//options.shuffle();
}
return WillPopScope(
onWillPop: _onWillPop,
child: Scaffold(
key: _key,
appBar: AppBar(
title: Text("Question No. - " + "${_currentIndex + 1}"),
backgroundColor: Colors.indigoAccent,
elevation: 10,
),
body: Center(
child: ListView(
shrinkWrap: true,
padding: EdgeInsets.all(15.0),
children: <Widget>[
Center(
child: Card(
elevation: 0.0,
child: Container(
//padding: EdgeInsets.all(0.0),
width: double.infinity,
height: 900,
child: Column(
children: <Widget>[
Row(
children: <Widget>[
//SizedBox(width: 10.0),
Expanded(
child: Text(
HtmlUnescape().convert(
widget.questions[_currentIndex].question),
softWrap: true,
textAlign: TextAlign.justify,
style: _questionStyle,
),
),
],
),
Row(
children: <Widget>[
//SizedBox(width: 10.0),
Expanded(
child: Image.network(
HtmlUnescape().convert(
widget.questions[_currentIndex].qimgurl),
// width: 300,
fit: BoxFit.fitWidth,
loadingBuilder: (BuildContext context,
Widget child,
ImageChunkEvent loadingProgress) {
if (loadingProgress == null) return child;
return Center(
child: CircularProgressIndicator(
value: loadingProgress.expectedTotalBytes !=
null
? loadingProgress
.cumulativeBytesLoaded /
loadingProgress.expectedTotalBytes
: null,
),
);
},
)),
],
),
//SizedBox(height: 0.0),
Card(
//elevation: 10.0,
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
...options.map((option) => RadioListTile(
title: Text(
HtmlUnescape().convert("$option"),
style: TextStyle(color: Colors.black),
),
groupValue: _answers[_currentIndex],
value: option,
onChanged: (value) {
setState(() {
_answers[_currentIndex] = option;
if (i == 0) {
option1 = option;
}
if (option ==
widget.questions[_currentIndex]
.correctAnswer) {
i = 1;
Fluttertoast.cancel();
Fluttertoast.showToast(
msg: "Righ Answer",
toastLength: Toast.LENGTH_SHORT,
gravity: ToastGravity.BOTTOM,
timeInSecForIosWeb: 1,
backgroundColor: Colors.green,
textColor: Colors.white,
fontSize: 16.0);
} else {
i = 1;
Fluttertoast.cancel();
Fluttertoast.showToast(
msg: "Wrong Answer",
toastLength: Toast.LENGTH_SHORT,
gravity: ToastGravity.BOTTOM,
timeInSecForIosWeb: 1,
backgroundColor: Colors.red,
textColor: Colors.white,
fontSize: 16.0);
}
});
},
)),
],
),
),
Expanded(
child: Container(
alignment: Alignment.topCenter,
child: new Row(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
/* const SizedBox(height: 30),*/
/* RaisedButton(
child: Text('Hint'),
onPressed:_giveHint,
color:Colors.yellow, ),*/
const SizedBox(),
ButtonTheme(
minWidth: 200,
height: 50,
child: RaisedButton(
child: Text(_currentIndex ==
(widget.questions.length - 1)
? "Submit"
: "Next"),
onPressed: _nextSubmit,
color: Colors.yellow,
),
),
],
),
),
)
],
),
),
),
),
],
),
),
),
);
}
void _nextSubmit() {
if (_answers[_currentIndex] == null) {
_key.currentState.showSnackBar(SnackBar(
content: Text("You must select an answer to continue."),
));
return;
}
if (_currentIndex < (widget.questions.length - 1)) {
_answers[_currentIndex] = option1;
showDialog(
context: context,
builder: (context) {
return AlertDialog(
title: Text('Answer is'),
content: Text(widget.questions[_currentIndex].correctAnswer),
actions: <Widget>[
FlatButton(
child: Text('Ok'),
onPressed: () {
Navigator.of(context).pop();
setState(() {
_currentIndex++;
i = 0;
});
},
),
],
);
});
} else {
Navigator.of(context).pushReplacement(MaterialPageRoute(
builder: (_) => QuizFinishedPage(
questions: widget.questions, answers: _answers)));
}
}
Future<bool> _onWillPop() async {
return showDialog<bool>(
context: context,
builder: (_) {
return AlertDialog(
content: Text(
"Are you sure you want to quit the quiz? All your progress will be lost."),
title: Text("Warning!"),
actions: <Widget>[
FlatButton(
child: Text("Yes"),
onPressed: () {
Navigator.pop(context, true);
},
),
FlatButton(
child: Text("No"),
onPressed: () {
Navigator.pop(context, false);
},
),
],
);
});
}
}
There is an activeColor property in RadioListTile which lets you change color of the tile when it's selected.You can add a condition using ternary operator as follows to do the work for you:
activeColor: (option ==
widget.questions[_currentIndex]
.correctAnswer) ? Colors.green : Colors.red,
Complete Code:
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:mechanicalaptitude/quiz/models/category.dart';
import 'package:mechanicalaptitude/quiz/models/question.dart';
import 'package:mechanicalaptitude/quiz/ui/pages/quiz_finished.dart';
import 'package:html_unescape/html_unescape.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:admob_flutter/admob_flutter.dart';
class QuizPage extends StatefulWidget {
final List<Question> questions;
final Category category;
const QuizPage({Key key, #required this.questions, this.category})
: super(key: key);
#override
_QuizPageState createState() => _QuizPageState();
}
class _QuizPageState extends State<QuizPage> {
final TextStyle _questionStyle = TextStyle(
fontSize: 18.0, //font size of the questions
fontWeight: FontWeight.bold,
color: Colors.red);
int _currentIndex = 0;
int i = 0;
int hint_index = 0;
var option1;
final Map<int, dynamic> _answers = {};
final GlobalKey<ScaffoldState> _key = GlobalKey<ScaffoldState>();
#override
Widget build(BuildContext context) {
Question question = widget.questions[_currentIndex];
final List<dynamic> options = question.incorrectAnswers;
if (!options.contains(question.correctAnswer)) {
options.add(question.correctAnswer);
//options.shuffle();
}
return WillPopScope(
onWillPop: _onWillPop,
child: Scaffold(
key: _key,
appBar: AppBar(
title: Text("Question No. - " + "${_currentIndex + 1}"),
backgroundColor: Colors.indigoAccent,
elevation: 10,
),
body: Center(
child: ListView(
shrinkWrap: true,
padding: EdgeInsets.all(15.0),
children: <Widget>[
Center(
child: Card(
elevation: 0.0,
child: Container(
//padding: EdgeInsets.all(0.0),
width: double.infinity,
height: 900,
child: Column(
children: <Widget>[
Row(
children: <Widget>[
//SizedBox(width: 10.0),
Expanded(
child: Text(
HtmlUnescape().convert(
widget.questions[_currentIndex].question),
softWrap: true,
textAlign: TextAlign.justify,
style: _questionStyle,
),
),
],
),
Row(
children: <Widget>[
//SizedBox(width: 10.0),
Expanded(
child: Image.network(
HtmlUnescape().convert(
widget.questions[_currentIndex].qimgurl),
// width: 300,
fit: BoxFit.fitWidth,
loadingBuilder: (BuildContext context,
Widget child,
ImageChunkEvent loadingProgress) {
if (loadingProgress == null) return child;
return Center(
child: CircularProgressIndicator(
value: loadingProgress.expectedTotalBytes !=
null
? loadingProgress
.cumulativeBytesLoaded /
loadingProgress.expectedTotalBytes
: null,
),
);
},
)),
],
),
//SizedBox(height: 0.0),
Card(
//elevation: 10.0,
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
...options.map((option) => RadioListTile(
title: Text(
HtmlUnescape().convert("$option"),
style: TextStyle(color: Colors.black),
),
activeColor: (option ==
widget.questions[_currentIndex]
.correctAnswer) ? Colors.green : Colors.red,
groupValue: _answers[_currentIndex],
value: option,
onChanged: (value) {
setState(() {
_answers[_currentIndex] = option;
if (i == 0) {
option1 = option;
}
if (option ==
widget.questions[_currentIndex]
.correctAnswer) {
i = 1;
Fluttertoast.cancel();
Fluttertoast.showToast(
msg: "Righ Answer",
toastLength: Toast.LENGTH_SHORT,
gravity: ToastGravity.BOTTOM,
timeInSecForIosWeb: 1,
backgroundColor: Colors.green,
textColor: Colors.white,
fontSize: 16.0);
} else {
i = 1;
Fluttertoast.cancel();
Fluttertoast.showToast(
msg: "Wrong Answer",
toastLength: Toast.LENGTH_SHORT,
gravity: ToastGravity.BOTTOM,
timeInSecForIosWeb: 1,
backgroundColor: Colors.red,
textColor: Colors.white,
fontSize: 16.0);
}
});
},
)),
],
),
),
Expanded(
child: Container(
alignment: Alignment.topCenter,
child: new Row(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
/* const SizedBox(height: 30),*/
/* RaisedButton(
child: Text('Hint'),
onPressed:_giveHint,
color:Colors.yellow, ),*/
const SizedBox(),
ButtonTheme(
minWidth: 200,
height: 50,
child: RaisedButton(
child: Text(_currentIndex ==
(widget.questions.length - 1)
? "Submit"
: "Next"),
onPressed: _nextSubmit,
color: Colors.yellow,
),
),
],
),
),
)
],
),
),
),
),
],
),
),
),
);
}
void _nextSubmit() {
if (_answers[_currentIndex] == null) {
_key.currentState.showSnackBar(SnackBar(
content: Text("You must select an answer to continue."),
));
return;
}
if (_currentIndex < (widget.questions.length - 1)) {
_answers[_currentIndex] = option1;
showDialog(
context: context,
builder: (context) {
return AlertDialog(
title: Text('Answer is'),
content: Text(widget.questions[_currentIndex].correctAnswer),
actions: <Widget>[
FlatButton(
child: Text('Ok'),
onPressed: () {
Navigator.of(context).pop();
setState(() {
_currentIndex++;
i = 0;
});
},
),
],
);
});
} else {
Navigator.of(context).pushReplacement(MaterialPageRoute(
builder: (_) => QuizFinishedPage(
questions: widget.questions, answers: _answers)));
}
}
Future<bool> _onWillPop() async {
return showDialog<bool>(
context: context,
builder: (_) {
return AlertDialog(
content: Text(
"Are you sure you want to quit the quiz? All your progress will be lost."),
title: Text("Warning!"),
actions: <Widget>[
FlatButton(
child: Text("Yes"),
onPressed: () {
Navigator.pop(context, true);
},
),
FlatButton(
child: Text("No"),
onPressed: () {
Navigator.pop(context, false);
},
),
],
);
});
}
}
I have a problem with my BottomNavigationBar in Flutter. I want to keep my page alive if I change the tabs.
here my implementation
BottomNavigation
class Home extends StatefulWidget {
#override
State<StatefulWidget> createState() {
return _HomeState();
}
}
class _HomeState extends State<Home> {
int _currentIndex = 0;
List<Widget> _children;
final Key keyOne = PageStorageKey("IndexTabWidget");
#override
void initState() {
_children = [
IndexTabWidget(key: keyOne),
PlaceholderWidget(Colors.green),
NewsListWidget(),
ShopsTabWidget(),
PlaceholderWidget(Colors.blue),
];
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(MyApp.appName),
textTheme: Theme.of(context).textTheme.apply(
bodyColor: Colors.black,
displayColor: Colors.blue,
),
),
body: _children[_currentIndex],
bottomNavigationBar: BottomNavigationBar(
onTap: onTabTapped,
key: IHGApp.globalKey,
fixedColor: Colors.green,
type: BottomNavigationBarType.fixed,
currentIndex: _currentIndex,
items: [
BottomNavigationBarItem(
icon: Icon(Icons.home),
title: Container(height: 0.0),
),
BottomNavigationBarItem(
icon: Icon(Icons.message),
title: Container(height: 0.0),
),
BottomNavigationBarItem(
icon: Icon(Icons.settings),
title: Container(height: 0.0),
),
BottomNavigationBarItem(
icon: Icon(Icons.perm_contact_calendar),
title: Container(height: 0.0),
),
BottomNavigationBarItem(
icon: Icon(Icons.business),
title: Container(height: 0.0),
),
],
),
);
}
void onTabTapped(int index) {
setState(() {
_currentIndex = index;
});
}
Column buildButtonColumn(IconData icon) {
Color color = Theme.of(context).primaryColor;
return Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: [
Icon(icon, color: color),
],
);
}
}
This is my index page (first tab):
class IndexTabWidget extends StatefulWidget {
IndexTabWidget({Key key}) : super(key: key);
#override
State<StatefulWidget> createState() {
return new IndexTabState();
}
}
class IndexTabState extends State<IndexTabWidget>
with AutomaticKeepAliveClientMixin {
List<News> news = List();
FirestoreNewsRepo newsFirestore = FirestoreNewsRepo();
#override
Widget build(BuildContext context) {
return Material(
color: Colors.white,
child: new Container(
child: new SingleChildScrollView(
child: new ConstrainedBox(
constraints: new BoxConstraints(),
child: new Column(
children: <Widget>[
HeaderWidget(
CachedNetworkImageProvider(
'https://static1.fashionbeans.com/wp-content/uploads/2018/04/50-barbershop-top-savill.jpg',
),
"",
),
AboutUsWidget(),
Padding(
padding: const EdgeInsets.all(16.0),
child: SectionTitleWidget(title: StringStorage.salonsTitle),
),
StreamBuilder(
stream: newsFirestore.observeNews(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return CircularProgressIndicator();
} else {
news = snapshot.data;
return Column(
children: <Widget>[
ShopItemWidget(
AssetImage('assets/images/picture.png'),
news[0].title,
news[0],
),
ShopItemWidget(
AssetImage('assets/images/picture1.png'),
news[1].title,
news[1],
)
],
);
}
},
),
Padding(
padding: const EdgeInsets.only(
left: 16.0, right: 16.0, bottom: 16.0),
child: SectionTitleWidget(title: StringStorage.galleryTitle),
),
GalleryCategoryCarouselWidget(),
],
),
),
),
),
);
}
#override
bool get wantKeepAlive => true;
}
So if I switch from my index tab to any other tab and back to the index tab, the index tab will always rebuild. I debugged it and saw that the build function is always being called on the tab switch.
Could you guys help me out with this issue?
Thank you a lot
Albo
None of the previous answers worked out for me.
The solution to keep the pages alive when switching the tabs is wrapping your Pages in an IndexedStack.
class Tabbar extends StatefulWidget {
Tabbar({this.screens});
static const Tag = "Tabbar";
final List<Widget> screens;
#override
State<StatefulWidget> createState() {
return _TabbarState();
}
}
class _TabbarState extends State<Tabbar> {
int _currentIndex = 0;
Widget currentScreen;
#override
Widget build(BuildContext context) {
var _l10n = PackedLocalizations.of(context);
return Scaffold(
body: IndexedStack(
index: _currentIndex,
children: widget.screens,
),
bottomNavigationBar: BottomNavigationBar(
fixedColor: Colors.black,
type: BottomNavigationBarType.fixed,
onTap: onTabTapped,
currentIndex: _currentIndex,
items: [
BottomNavigationBarItem(
icon: new Icon(Icons.format_list_bulleted),
title: new Text(_l10n.tripsTitle),
),
BottomNavigationBarItem(
icon: new Icon(Icons.settings),
title: new Text(_l10n.settingsTitle),
)
],
),
);
}
void onTabTapped(int index) {
setState(() {
_currentIndex = index;
});
}
}
You need to wrap every root page (the first page you see when you press a bottom navigation item) with a navigator and put them in a Stack.
class HomePage extends StatefulWidget {
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
final int _pageCount = 2;
int _pageIndex = 0;
#override
Widget build(BuildContext context) {
return Scaffold(
body: _body(),
bottomNavigationBar: _bottomNavigationBar(),
);
}
Widget _body() {
return Stack(
children: List<Widget>.generate(_pageCount, (int index) {
return IgnorePointer(
ignoring: index != _pageIndex,
child: Opacity(
opacity: _pageIndex == index ? 1.0 : 0.0,
child: Navigator(
onGenerateRoute: (RouteSettings settings) {
return new MaterialPageRoute(
builder: (_) => _page(index),
settings: settings,
);
},
),
),
);
}),
);
}
Widget _page(int index) {
switch (index) {
case 0:
return Page1();
case 1:
return Page2();
}
throw "Invalid index $index";
}
BottomNavigationBar _bottomNavigationBar() {
final theme = Theme.of(context);
return new BottomNavigationBar(
fixedColor: theme.accentColor,
currentIndex: _pageIndex,
items: [
BottomNavigationBarItem(
icon: Icon(Icons.list),
title: Text("Page 1"),
),
BottomNavigationBarItem(
icon: Icon(Icons.account_circle),
title: Text("Page 2"),
),
],
onTap: (int index) {
setState(() {
_pageIndex = index;
});
},
);
}
}
The pages will be rebuild but you should separate your business logic from you UI anyway. I prefer to use the BLoC pattern but you can also use Redux, ScopedModel or InhertedWidget.
Just use an IndexedStack
IndexedStack(
index: selectedIndex,
children: <Widget> [
ProfileScreen(),
MapScreen(),
FriendsScreen()
],
)
I'm not sure but CupertinoTabBar would help.
If you don't want it, this video would be great url.
import 'dart:async';
import 'dart:io';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_inapp_purchase/flutter_inapp_purchase.dart';
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => new _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
final List<dynamic> pages = [
new Page1(),
new Page2(),
new Page3(),
new Page4(),
];
int currentIndex = 0;
#override
Widget build(BuildContext context) {
return new WillPopScope(
onWillPop: () async {
await Future<bool>.value(true);
},
child: new CupertinoTabScaffold(
tabBar: new CupertinoTabBar(
iconSize: 35.0,
onTap: (index) {
setState(() => currentIndex = index);
},
activeColor: currentIndex == 0 ? Colors.white : Colors.black,
inactiveColor: currentIndex == 0 ? Colors.green : Colors.grey,
backgroundColor: currentIndex == 0 ? Colors.black : Colors.white,
currentIndex: currentIndex,
items: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.looks_one),
title: Text(''),
),
BottomNavigationBarItem(
icon: Icon(Icons.looks_two),
title: Text(''),
),
BottomNavigationBarItem(
icon: Icon(Icons.looks_3),
title: Text(''),
),
BottomNavigationBarItem(
icon: Icon(Icons.looks_4),
title: Text(''),
),
],
),
tabBuilder: (BuildContext context, int index) {
return new DefaultTextStyle(
style: const TextStyle(
fontFamily: '.SF UI Text',
fontSize: 17.0,
color: CupertinoColors.black,
),
child: new CupertinoTabView(
routes: <String, WidgetBuilder>{
'/Page1': (BuildContext context) => new Page1(),
'/Page2': (BuildContext context) => new Page2(),
'/Page3': (BuildContext context) => new Page3(),
'/Page4': (BuildContext context) => new Page4(),
},
builder: (BuildContext context) {
return pages[currentIndex];
},
),
);
},
),
);
}
}
class Page1 extends StatefulWidget {
#override
_Page1State createState() => _Page1State();
}
class _Page1State extends State<Page1> {
String title;
#override
void initState() {
title = 'Page1';
super.initState();
}
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text(title),
leading: new IconButton(
icon: new Icon(Icons.text_fields),
onPressed: () {
Navigator.of(context)
.push(MaterialPageRoute(builder: (context) => Page13()));
},
)),
body: new Center(
child: new Text(title),
),
);
}
}
class Page2 extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Page2'),
leading: new IconButton(
icon: new Icon(Icons.airline_seat_flat_angled),
onPressed: () {
Navigator.of(context)
.push(MaterialPageRoute(builder: (context) => Page12()));
},
)),
body: new Center(
child: Column(
children: <Widget>[
CupertinoSlider(
value: 25.0,
min: 0.0,
max: 100.0,
onChanged: (double value) {
print(value);
}
),
],
),
),
);
}
}
class Page3 extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Page3'),
),
body: new Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new RaisedButton(
child: new Text('Cupertino'),
textColor: Colors.white,
color: Colors.red,
onPressed: () {
List<int> list = List.generate(10, (int i) => i + 1);
list.shuffle();
var subList = (list.sublist(0, 5));
print(subList);
subList.forEach((li) => list.remove(li));
print(list);
}
),
new SizedBox(height: 30.0),
new RaisedButton(
child: new Text('Android'),
textColor: Colors.white,
color: Colors.lightBlue,
onPressed: () {
var mes = 'message';
var messa = 'メッセージ';
var input = 'You have a new message';
if (input.contains(messa) || input.contains(mes)) {
print('object');
} else {
print('none');
}
}
),
],
),
),
);
}
}
class Page4 extends StatelessWidget {
static List<int> ints = [1, 2, 3, 4, 5];
static _abc() {
print(ints.last);
}
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Page4'),
),
body: new Center(
child: new RaisedButton(
child: new Text('Static', style: new TextStyle(color: Colors.white)),
color: Colors.lightBlue,
onPressed: _abc,
)),
);
}
}
class Page12 extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Page12'),
actions: <Widget>[
new FlatButton(
child: new Text('GO'),
onPressed: () {
Navigator.of(context)
.push(MaterialPageRoute(builder: (context) => Page13()));
},
)
],
),
body: new Center(
child: new RaisedButton(
child: new Text('Swiper', style: new TextStyle(color: Colors.white)),
color: Colors.redAccent,
onPressed: () {},
)),
);
}
}
class Page13 extends StatefulWidget {
#override
_Page13State createState() => _Page13State();
}
class _Page13State extends State<Page13> with SingleTickerProviderStateMixin {
final List<String> _productLists = Platform.isAndroid
? [
'android.test.purchased',
'point_1000',
'5000_point',
'android.test.canceled',
]
: ['com.cooni.point1000', 'com.cooni.point5000'];
String _platformVersion = 'Unknown';
List<IAPItem> _items = [];
List<PurchasedItem> _purchases = [];
#override
void initState() {
super.initState();
initPlatformState();
}
Future<void> initPlatformState() async {
String platformVersion;
try {
platformVersion = await FlutterInappPurchase.platformVersion;
} on PlatformException {
platformVersion = 'Failed to get platform version.';
}
var result = await FlutterInappPurchase.initConnection;
print('result: $result');
if (!mounted) return;
setState(() {
_platformVersion = platformVersion;
});
// refresh items for android
String msg = await FlutterInappPurchase.consumeAllItems;
print('consumeAllItems: $msg');
}
Future<Null> _buyProduct(IAPItem item) async {
try {
PurchasedItem purchased = await FlutterInappPurchase.buyProduct(item.productId);
print('purchased: ${purchased.toString()}');
} catch (error) {
print('$error');
}
}
Future<Null> _getProduct() async {
List<IAPItem> items = await FlutterInappPurchase.getProducts(_productLists);
print(items);
for (var item in items) {
print('${item.toString()}');
this._items.add(item);
}
setState(() {
this._items = items;
this._purchases = [];
});
}
Future<Null> _getPurchases() async {
List<PurchasedItem> items = await FlutterInappPurchase.getAvailablePurchases();
for (var item in items) {
print('${item.toString()}');
this._purchases.add(item);
}
setState(() {
this._items = [];
this._purchases = items;
});
}
Future<Null> _getPurchaseHistory() async {
List<PurchasedItem> items = await FlutterInappPurchase.getPurchaseHistory();
for (var item in items) {
print('${item.toString()}');
this._purchases.add(item);
}
setState(() {
this._items = [];
this._purchases = items;
});
}
List<Widget> _renderInApps() {
List<Widget> widgets = this
._items
.map((item) => Container(
margin: EdgeInsets.symmetric(vertical: 10.0),
child: Container(
child: Column(
children: <Widget>[
Container(
margin: EdgeInsets.only(bottom: 5.0),
child: Text(
item.toString(),
style: TextStyle(
fontSize: 18.0,
color: Colors.black,
),
),
),
FlatButton(
color: Colors.orange,
onPressed: () {
print("---------- Buy Item Button Pressed");
this._buyProduct(item);
},
child: Row(
children: <Widget>[
Expanded(
child: Container(
height: 48.0,
alignment: Alignment(-1.0, 0.0),
child: Text('Buy Item'),
),
),
],
),
),
],
),
),
))
.toList();
return widgets;
}
List<Widget> _renderPurchases() {
List<Widget> widgets = this
._purchases
.map((item) => Container(
margin: EdgeInsets.symmetric(vertical: 10.0),
child: Container(
child: Column(
children: <Widget>[
Container(
margin: EdgeInsets.only(bottom: 5.0),
child: Text(
item.toString(),
style: TextStyle(
fontSize: 18.0,
color: Colors.black,
),
),
)
],
),
),
))
.toList();
return widgets;
}
#override
Widget build(BuildContext context) {
double screenWidth = MediaQuery.of(context).size.width-20;
double buttonWidth=(screenWidth/3)-20;
return new Scaffold(
appBar: new AppBar(),
body: Container(
padding: EdgeInsets.all(10.0),
child: ListView(
children: <Widget>[
Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Container(
child: Text(
'Running on: $_platformVersion\n',
style: TextStyle(fontSize: 18.0),
),
),
Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Container(
width: buttonWidth,
height: 60.0,
margin: EdgeInsets.all(7.0),
child: FlatButton(
color: Colors.amber,
padding: EdgeInsets.all(0.0),
onPressed: () async {
print("---------- Connect Billing Button Pressed");
await FlutterInappPurchase.initConnection;
},
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20.0),
alignment: Alignment(0.0, 0.0),
child: Text(
'Connect Billing',
style: TextStyle(
fontSize: 16.0,
),
),
),
),
),
Container(
width: buttonWidth,
height: 60.0,
margin: EdgeInsets.all(7.0),
child: FlatButton(
color: Colors.amber,
padding: EdgeInsets.all(0.0),
onPressed: () async {
print("---------- End Connection Button Pressed");
await FlutterInappPurchase.endConnection;
setState(() {
this._items = [];
this._purchases = [];
});
},
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20.0),
alignment: Alignment(0.0, 0.0),
child: Text(
'End Connection',
style: TextStyle(
fontSize: 16.0,
),
),
),
),
),
],
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Container(
width: buttonWidth,
height: 60.0,
margin: EdgeInsets.all(7.0),
child: FlatButton(
color: Colors.green,
padding: EdgeInsets.all(0.0),
onPressed: () {
print("---------- Get Items Button Pressed");
this._getProduct();
},
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20.0),
alignment: Alignment(0.0, 0.0),
child: Text(
'Get Items',
style: TextStyle(
fontSize: 16.0,
),
),
),
)),
Container(
width: buttonWidth,
height: 60.0,
margin: EdgeInsets.all(7.0),
child: FlatButton(
color: Colors.green,
padding: EdgeInsets.all(0.0),
onPressed: () {
print(
"---------- Get Purchases Button Pressed");
this._getPurchases();
},
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20.0),
alignment: Alignment(0.0, 0.0),
child: Text(
'Get Purchases',
style: TextStyle(
fontSize: 16.0,
),
),
),
)),
Container(
width: buttonWidth,
height: 60.0,
margin: EdgeInsets.all(7.0),
child: FlatButton(
color: Colors.green,
padding: EdgeInsets.all(0.0),
onPressed: () {
print(
"---------- Get Purchase History Button Pressed");
this._getPurchaseHistory();
},
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20.0),
alignment: Alignment(0.0, 0.0),
child: Text(
'Get Purchase History',
style: TextStyle(
fontSize: 16.0,
),
),
),
)),
]),
],
),
Column(
children: this._renderInApps(),
),
Column(
children: this._renderPurchases(),
),
],
),
],
),
),
);
}
}
Use IndexedStack widget:
class Home extends StatefulWidget {
const Home({Key? key}) : super(key: key);
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
int _currentIndex = 0;
#override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
child: IndexedStack(
index: _currentIndex,
children: const [
HomePage(),
SettingsPage(),
],
),
),
bottomNavigationBar: BottomNavigationBar(
currentIndex: _currentIndex,
onTap: (int index) => setState(() => _currentIndex = index),
items: [
BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Home'),
BottomNavigationBarItem(icon: Icon(Icons.settings), label: 'Settings'),
],
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
print('build home');
return Center(child: Text('Home'));
}
}
class SettingsPage extends StatelessWidget {
const SettingsPage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
print('build settings');
return Center(child: Text('Settings'));
}
}
Make sure the IndexedStack children widget list is constant. This will prevent the widgets from rebuilding when setState() is called.
IndexedStack(
index: _currentIndex,
children: const [
HomeWidget(),
SettingsWidget(),
],
),
The problem with IndexedStack is that all the widgets will be built at the same time when IndexedStack is initialized. For small widgets (like the example above), it won't be a problem. But for big widgets, you may see some performance issues.
Consider using the lazy_load_indexed_stack package. According to the package:
[LazyLoadIndexedStack widget] builds the required widget only when it is needed, and returns the pre-built widget when it is needed again
Again, make sure the LazyLoadIndexedStack children widgets are constant, otherwise they will keep rebuilding when setState is called.
If, you just need to remember the scroll position inside a list, the best option is to simply use a PageStoreKey object for the key property:
#override
Widget build(BuildContext context) {
return Container(
child: ListView.builder(
key: PageStorageKey<String>('some-list-key'),
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemCount: items.length,
itemBuilder: (BuildContext context, int index) {
return GestureDetector(
onTap: () => _onElementTapped(index),
child: makeCard(items[index])
);
},
),
);
}
According to https://docs.flutter.io/flutter/widgets/PageStorageKey-class.html, this should work on ANY scrollable widget.
if i use the IndexedStack in the body it is loading only the main screen content not every other screen which is present in the bottom nativation bar.
Using IndexedStack with bloc pattern solved everthing.