main.dart

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';

void main() => runApp(new CupertinoApp(
      home: Home(),
      debugShowCheckedModeBanner: false,
    ));

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      navigationBar: CupertinoNavigationBar(
        middle: Text("Alert Dialog"),
      ),
      child: Container(
        child: Center(
          child: CupertinoButton(
            onPressed: () {
              showCupertinoDialog(
                  context: context,
                  builder: (context) {
                    return CupertinoAlertDialog(
                      title: Text("Warning"),
                      content: Text("Are you sure want to delete this data?"),
                      actions: <Widget>[
                        CupertinoDialogAction(
                          child: Text("No"),
                          onPressed: () {
                          },
                        ),
                        CupertinoDialogAction(
                          child: Text("Yes"),
                          onPressed: () {
                          },
                          isDestructiveAction: true,
                        ),
                      ],
                    );
                  });
            },
            child: Text("Tap me"),
          ),
        ),
      ),
    );
  }
}