How do I call method of child widget?
class Parent extends StatefulWidget {
const Parent({Key? key}) : super(key: key);
@override
State<Parent> createState() => _ParentState();
}
class _ParentState extends State<Parent> {
@override
Widget build(BuildContext context) {
return Column(
children: [
FloatingActionButton(onPressed: (){
//call child function named funcToCallFromParent
}),
Child(),
],
);
}
}
class Child extends StatefulWidget {
const Child({Key? key}) : super(key: key);
@override
State<Child> createState() => _ChildState();
}
class _ChildState extends State<Child> {
void funcToCallFromParent(){
print('child func called from parent');
}
@override
Widget build(BuildContext context) {
return Container();
}
}
CodePudding user response:
You can use a GlobalKey
for that.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
final String title;
const MyHomePage({
Key? key,
required this.title,
}) : super(key: key);
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final _key = GlobalKey<_ChildState>();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(child: Child(key: _key)),
floatingActionButton: FloatingActionButton(
onPressed: () {
// The current state can be null,
// i.e. there is no widget in the tree because it has been unmounted.
_key.currentState?.funcToCallFromParent();
},
tooltip: 'Increment',
child: const Icon(Icons.add),
),
);
}
}
class Child extends StatefulWidget {
const Child({Key? key}) : super(key: key);
@override
State<Child> createState() => _ChildState();
}
class _ChildState extends State<Child> {
void funcToCallFromParent() {
print('child func called from parent');
}
@override
Widget build(BuildContext context) {
return Container();
}
}
See https://api.flutter.dev/flutter/widgets/GlobalKey-class.html
CodePudding user response:
You can use ChangeNotifier
to notify the child (or children if you have more than one child that need to be notified) when the parent's button is pressed:
class FloatingActionButtonNotifier extends ChangeNotifier {
void onFloatingActionButtonPressed() => notifyListeners();
}
class Parent extends StatefulWidget {
const Parent({super.key});
@override
State<Parent> createState() => _ParentState();
}
class _ParentState extends State<Parent> {
final FloatingActionButtonNotifier fabNotifier = FloatingActionButtonNotifier();
@override
Widget build(BuildContext context) {
return Column(
children: [
FloatingActionButton(onPressed: fabNotifier.onFloatingActionButtonPressed),
Child(fabNotifier: fabNotifier),
],
);
}
}
class Child extends StatefulWidget {
const Child({
super.key,
required this.fabNotifier,
});
final FloatingActionButtonNotifier fabNotifier;
@override
State<Child> createState() => _ChildState();
}
class _ChildState extends State<Child> {
void funcToCallFromParent() {
print('child func called from parent');
}
@override
void initState() {
super.initState();
widget.fabNotifier.addListener(funcToCallFromParent);
}
@override
void dispose() {
super.dispose();
widget.fabNotifier.removeListener(funcToCallFromParent);
}
@override
Widget build(BuildContext context) {
return Container();
}
}
CodePudding user response:
You can use GlobalKey for Child, and get the state of Child(StatefulWidget). Then call the child's function in the parent widget.
GlobalKey<MyHomePageState> homePageStateKey = GlobalKey<MyHomePageState>();
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
homePageStateKey.currentState?._incrementCounterAfterOneSecond();
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(key: homePageStateKey, title: 'Flutter Demo Home Page'),
);
}
}