How to implement Gesture detection - On Tap method in child class? - flutter

Question

I want to implement the GestureDetector method onTapin child class. Is there a way to do it in Flutter ?
ParentClass.dart
Class ParentClass extends StatelessWidget {
#override
Widget build(BuildContext context) {
return GestureDetector {
onTap: methodA,
child: ChildClass(),
}
}
ChildClass.dart
Class ChildClass extends StatefulWidget {
methodA() // need to access methodA which is being passed to gesture detector
// How do I access methodA of parent class method here
// so whenever GestureDetector's onTap method is called, i want to handle that in ChildClass is there a way to do it ?
}

Answer 1

You can access the Child State methods using a unique key. Here is a minimal example:
Inside the ParentWidget, we define _childKey, a GlobalKey<_ChildWidgetState> that we then can use to access the State's method updateValue as follows:
_childKey.currentState.updateValue('Goodbye, Thierry!'),
Full source code
import 'package:flutter/material.dart';
void main() {
runApp(
MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Flutter Demo',
home: HomePage(),
),
);
}
class HomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(child: ParentWidget()),
);
}
}
class ParentWidget extends StatefulWidget {
#override
_ParentWidgetState createState() => _ParentWidgetState();
}
class _ParentWidgetState extends State<ParentWidget> {
final _childKey = GlobalKey<_ChildWidgetState>();
#override
Widget build(BuildContext context) {
return GestureDetector(
onTap: () => _childKey.currentState.updateValue('Goodbye, Thierry!'),
child: ChildWidget(key: _childKey),
);
}
}
class ChildWidget extends StatefulWidget {
const ChildWidget({Key key}) : super(key: key);
#override
_ChildWidgetState createState() => _ChildWidgetState();
}
class _ChildWidgetState extends State<ChildWidget> {
String value = 'Hello, Thierry!';
void updateValue(String newValue) {
setState(() => value = newValue);
}
#override
Widget build(BuildContext context) {
return Text(value);
}
}

Answer 2

In your ChildClass, return a GestureDetector. Set the child property to the rest of your widgets, and then set the onTap to call methodA. That should look something like this:
class ChildClass extends StatelessWidget {
#override
Widget build(BuildContext context) {
return GestureDetector {
onTap: methodA,
child: SomeWidget(),
}
}

Answer 3

You are asking how to detect child class onTap and pass it to Parent right?
class YourChild extends StatelessWidget {
final Function parentCallback;
const YourChild({this.parentCallback});
#override
Widget build(BuildContext context) {
return GestureDetector(
// 1st option
onTap: () {
print("do something");
parentCallback();
},
)
}
}
Then for using It.
class YourParent extends StatelessWidget {
#override
Widget build(BuildContext context) {
return YourChild( parentCallback(){
//do your stuff}
)
}
}