keep rotation loceked in flutter code example

Example 1: flutter lock orientation for page

@override
dispose(){
  SystemChrome.setPreferredOrientations([
    DeviceOrientation.landscapeRight,
    DeviceOrientation.landscapeLeft,
    DeviceOrientation.portraitUp,
    DeviceOrientation.portraitDown,
  ]);
  super.dispose();
}

Example 2: flutter lock orientation

import 'package:flutter/material.dart';  import 'package:flutter/services.dart';   Future main() async {    await SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);    runApp(new MyApp());  }   class MyApp extends StatelessWidget {    @override      Widget build(BuildContext context) {      return MaterialApp(        title: 'Welcome to Flutter',        home: Scaffold(          appBar: AppBar(            title: Text('Flutter Display Orientation Tutorial'),          ),          body: Center(            child: Text(                "Woolha.com"            )          ),        ),      );    }  }