首先导入服务包：

import 'package:flutter/services.dart';

这将使您可以访问SystemChrome课程"Controls specific aspects of the operating system's graphical interface and how it interacts with the application."

加载小部件时，请执行以下操作：

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

然后当我离开页面时，将其恢复为正常状态，如下所示：

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