Flutter: How to set and lock screen orientation on-demand

First import the services package:

import 'package:flutter/services.dart';

This will give you access to the SystemChrome class, which "Controls specific aspects of the operating system's graphical interface and how it interacts with the application."

When you load the Widget, do something like this:

@override
void initState(){
  super.initState();
  SystemChrome.setPreferredOrientations([
      DeviceOrientation.landscapeRight,
      DeviceOrientation.landscapeLeft,
  ]);
}

then when I leave the page, put it back to normal like this:

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