alert_dialog.dart

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(
      debugShowCheckedModeBanner: false,
      home: StrangeWidget(),
    ),
  );
}

class StrangeWidget extends StatefulWidget {
  @override
  _StrangeWidgetState createState() => _StrangeWidgetState();
}

class _StrangeWidgetState extends State<StrangeWidget> {
  String input = "CLICA ALI";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: Text(input),
      ),
      floatingActionButton: FloatingActionButton(
        child: Text('AQUI'),
        onPressed: () async {
          String response = await showDialog(
            context: context,
            builder: (context) =>
                AlertDialog(title: Text('Eu ja dizia:'), actions: [
              FlatButton(
                child: Text('A vida'),
                onPressed: () => Navigator.of(context).pop('A vida'),
              ),
              FlatButton(
                child: Text('nao e'),
                onPressed: () => Navigator.of(context).pop('nao e'),
              ),
              FlatButton(
                child: Text('um 🍓'),
                onPressed: () => Navigator.of(context).pop('um 🍓'),
              ),
            ]),
          );
          setState(() => input = response);
        },
      ),
    );
  }
}