MenuController + didChangeDependencies

main.dart

import 'package:flutter/material.dart';

void main() => runApp(const SampleApp());

class SampleApp extends StatefulWidget {
  const SampleApp({super.key});

  @override
  State<SampleApp> createState() => _SampleAppState();
}

class _SampleAppState extends State<SampleApp> {
  bool isShowing = false;
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(home: Scaffold(body: Sample(isShowing: true)));
  }
}

class Sample extends StatefulWidget {
  const Sample({super.key, required this.isShowing});

  final bool isShowing;

  @override
  State<Sample> createState() => _SampleState();
}

class _SampleState extends State<Sample> {
  final controller = MenuController();
  Size? size;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (size != null) {
      controller.open();
    }
    size ??= MediaQuery.sizeOf(context);
  }

  @override
  Widget build(BuildContext context) {
    return RawMenuAnchor(
      controller: controller,
      builder: (
        BuildContext context,
        MenuController controller,
        Widget? child,
      ) {
        return ElevatedButton(
          onPressed: () {
            if (controller.isOpen) {
              controller.close();
            } else {
              controller.open();
            }
          },
          child: const Text('Open'),
        );
      },
      overlayBuilder: (BuildContext context, RawMenuOverlayInfo info) {
        return Container(
          color: Colors.red,
          width: 200,
          height: 200,
          child: const Center(child: Text('Overlay')),
        );
      },
    );
  }
}