import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(body: Center(child: MyWidget())),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    WidgetsBinding.instance.addPostFrameCallback((timestamp) {
      showTimePicker(
        context: context,
        initialTime: TimeOfDay.now(),
        orientation: Orientation.portrait,
      );
    });

    return Container(height: 300, width: 100);
  }
}