Global key

https://api.flutter.dev/flutter/widgets/GlobalKey-class.html

GlobalKey class - widgets library - Dart API

특정 stateful위젯의 state위젯에 접근하게 해준다.

 

최소 예제

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyKey(),
    );
  }
}

class MyKey extends StatelessWidget {
  final counterKey = GlobalKey<_CounterState>();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Counter(
          key: counterKey,
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          counterKey.currentState!.increment();
        },
        child: Icon(Icons.add),
      ),
    );
  }
}

class Counter extends StatefulWidget {
  const Counter({Key? key}) : super(key: key);

  @override
  State<Counter> createState() => _CounterState();
}

class _CounterState extends State<Counter> {
  int count = 0;
  @override
  Widget build(BuildContext context) {
    return Text('$count');
  }

  void increment() {
    setState(() {
      count++;
    });
  }
}

- 글로벌 키 생성
final counterKey = GlobalKey<_CounterState>();

- 해당키를 stateful위젯의 생성자에 넣음
Counter(key: counterKey,)

- 위젯의 state내부의 메서드를 사용
counterKey.currentState!.increment();