Flutter Custom Multi Selection - flutter

Question

Question
Hi, how can I implement a custom multi selection widget in flutter? Here is an example :
I have a list of widget created with a ListView.builder and I simply want to change color based on userTap.
How can I implement this? I'm able to change color when user tap on one option but then, when another button is tapped I can't understand how to reverse the state of the old selected option.
I was searching for a solution with flutter standard state management or maybe with bloc library.
example code
class Test extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.builder(
itemCount: 10,
itemBuilder: (context, index){
return Padding(
padding: const EdgeInsets.only(bottom: 8.0),
child: SelectableContainer(text: 'option', index: index,),
);
},
),
);
}
}
class SelectableContainer extends StatefulWidget {
final String text;
final int index;
SelectableContainer({
#required this.text,
#required this.index
});
#override
_SelectableContainerState createState() => _SelectableContainerState();
}
class _SelectableContainerState extends State<SelectableContainer> {
bool _isSelected = false;
Color unselectedColor = Colors.white;
Color selectedColor = Colors.blue;
#override
Widget build(BuildContext context) {
return GestureDetector(
onTap: (){
setState(() {
_isSelected = true;
});
},
child: AnimatedContainer(
duration: Duration(milliseconds: 400),
height: 50,
color: _isSelected ? selectedColor : unselectedColor,
child: Center(
child: Text(widget.text),
),
),
);
}
}
Thanks

Answer 1

First store the selection in list when the user select an item
selectionList.add(title.id);
Then in the ListView.builder change the color of the title if it's in the selectionList
Title(color: selectionList.contain(listOfTitls[index].id)? Colors.green : Colors.White);
update
this trick will do it for you
return GestureDetector(
onTap: (){
setState(() {
_isSelected =_isSelected? false:true;//this line
});
},

Answer 2

In your setState method, you can just do _isSelected = !_isSelected; instead of always setting it to true. That way the tile will get unselected if _isSelected is set to true.
Although the above way wil solve your problem, there is also another widget flutter has for this same scenario called ListTile. Here is a link to the documentation. You might also want to check that out. It also has an onTap callback built into it directly.
Here is a quick app I built using ListTile. Hope it solves your problem. Cheers!
import 'package:flutter/material.dart';
class DemoClass extends StatefulWidget {
_DemoClassState createState() => _DemoClassState();
}
class _DemoClassState extends State<DemoClass> {
int _selectedIndex = -1;
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: ListView.builder(
itemCount: 10,
itemBuilder: (context, index) {
return AnimatedContainer(
duration: Duration(milliseconds: 300),
height: 50,
color: _selectedIndex == index ? Colors.blue : Colors.transparent,
child: ListTile(
title: Text('This is some title'),
onTap: () => setState(() {
_selectedIndex = index;
}),
),
);
}
),
);
}
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Center(
child: Container(
child: DemoClass(),
),
),
);
}
}
void main() {
runApp(MyApp());
}