Update child from parent in Flutter - flutter

Question

Currently, I have two sample files Parent.dart and Child.dart.
In Parent.dart file this is what the code is like:
Parent.dart file:
children:
[
isDisabled
? Icon(Icons.public, color: Colors.grey)
: Icon(Icons.public, color:Colors.white),
InkWell(
onTap:()=> Navigator.push(context,MaterialPageRoute(builder: (context)=> Child(
isDisabled: isDisabled, function: ()=> function())),
]
function()
{
setState(()=> isDisabled = !isDisabled);
}
and in Child.dart the code is something like this:
children:
[
widget.isDisabled
? Icon(Icons.public, color: Colors.grey)
: Icon(Icons.public, color:Colors.white),
InkWell(
onTap:()=> widget.function(),
]
I have some data being fetched from a server that is used to populate a list of cards inside listview.builder.
What I'm trying to do is inherent variables from the parent and use their value to update the child. Currently, if I run this parent does change, but the child doesn't until you navigate back from parent to child.
For a better context: Imagine a list of cards. Each has an add-to-list button. Now if you click on the card it goes to another screen "child.dart" where it gives you more details about the item on the card you clicked. Now if you click the add-to-list button on the child screen it should also update the parent.
I tried different ways of achieving this "UI synchrony" for a better user experience. But I didn't find a proper way to implement it.
Things I tried: Provider (but it updates all the items on the list instead of each instance.),
a "hacky" method of editing the data in the list on the client side and updating the widget based on that. (This technique does work, but ewwwww)

Answer 1

I'm not really sure to understand your question.
If your question is how trigger a function in parent from child screen, here is your answer.
I made a working example. I think you were really close.
Another option for state management is riverpod 2.0
Or you can pass value in Navigator.pop and trigger the function in parent.
Parent model
class Parent {
String title;
bool isDisabled = false;
Parent({required this.title});
}
Main.dart
import 'package:flutter/material.dart';
import 'parent.dart';
import 'ParentCard.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
MyApp({super.key});
List<Parent> parentList = [Parent(title: 'Item 1'), Parent(title: 'Item 2')];
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
body: ListView.builder(
itemCount: parentList.length,
itemBuilder: (BuildContext context, int position) {
return ParentCard(title: parentList[position].title);
},
),
),
);
}
}
ParentCard.dart
import 'package:flutter/material.dart';
import 'child.dart';
class ParentCard extends StatefulWidget {
String title;
ParentCard({super.key, required this.title});
#override
State<ParentCard> createState() => _ParentCardState();
}
class _ParentCardState extends State<ParentCard> {
bool isDisabled = false;
#override
Widget build(BuildContext context) {
return Row(
children: [
Text(widget.title),
isDisabled
? Icon(Icons.public, color: Colors.green)
: Icon(Icons.public, color: Colors.black),
IconButton(
icon: Icon(Icons.plus_one),
onPressed: () => Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
ChildCard(isDisabled: isDisabled, handler: handler)),
),
)
],
);
}
handler() {
setState(() => isDisabled = !isDisabled);
}
}
** child.dart**
import 'package:flutter/material.dart';
class ChildCard extends StatefulWidget {
VoidCallback handler;
bool isDisabled;
ChildCard({super.key, required this.isDisabled, required this.handler});
#override
State<ChildCard> createState() => _ChildCardState();
}
class _ChildCardState extends State<ChildCard> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(children: [
const Text('child !'),
widget.isDisabled
? const Icon(Icons.public, color: Colors.green)
: const Icon(Icons.public, color: Colors.black),
ElevatedButton(
onPressed: () {
setState(() {
widget.isDisabled = !widget.isDisabled;
});
widget.handler();
},
child: const Text('click to trigger'),
),
ElevatedButton(
onPressed: () {
Navigator.pop(context);
},
child: const Text('pop it'),
)
]),
);
}
}