Overlay example

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(
      home: MyHomePage(),
    ),
  );
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Overlay Example"),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            OverlayMessage(context).showOverlayMessage(
              "¡Hola!",
              "Este es un mensaje en overlay.",
            );
          },
          child: Text("Mostrar Overlay"),
        ),
      ),
    );
  }
}

class OverlayMessage {
  final BuildContext context;
  OverlayEntry? _overlayEntry;

  OverlayMessage(this.context);

  void showOverlayMessage(String title, String subtitle) {
    _overlayEntry = OverlayEntry(
      builder: (context) => Positioned(
        top: 50.0,
        left: MediaQuery.of(context).size.width * 0.1,
        right: MediaQuery.of(context).size.width * 0.1,
        child: Material(
          color: Colors.transparent,
          child: Stack(
            children: [
              Container(
                width: double.infinity,
                padding: EdgeInsets.all(16.0),
                decoration: BoxDecoration(
                  color: Colors.white,
                  borderRadius: BorderRadius.circular(10.0),
                  boxShadow: [
                    BoxShadow(
                      color: Colors.black26,
                      blurRadius: 10.0,
                      offset: Offset(0, 4),
                    ),
                  ],
                ),
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Text(
                      title,
                      style: TextStyle(
                        fontSize: 18.0,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                    SizedBox(height: 8.0),
                    Text(
                      subtitle,
                      style: TextStyle(
                        fontSize: 16.0,
                      ),
                    ),
                  ],
                ),
              ),
              Positioned(
                right: 8.0,
                top: 8.0,
                child: GestureDetector(
                  onTap: () {
                    _removeOverlay();
                  },
                  child: Icon(
                    Icons.close,
                    color: Colors.black,
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );

    Overlay.of(context).insert(_overlayEntry!);
  }

  void _removeOverlay() {
    _overlayEntry?.remove();
    _overlayEntry = null;
  }
}