HarmonyOS 鸿蒙Next竖屏显示如何切换横屏显示

通过setPreferredOrientation来设置主窗口的显示方向属性来实现切换横屏，PORTRAIT为竖屏显示，LANDSCAPE为横屏显示，文档参考：

https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-window-V5#setpreferredorientation9

示例：

import window from '@ohos.window';
import common from '@ohos.app.ability.common';
let win: window.Window | undefined = undefined
@Entry
@Component
struct Index {
  @State message: string = '竖屏';
  // 是否横屏
  @State isLandscape: boolean = false;
  // 获取UIAbility实例的上下文信息
  private context: common.UIAbilityContext = getContext(this) as common.UIAbilityContext;
  aboutToAppear() {
    window.getLastWindow(this.context).then((lastWindow) => {
      win = lastWindow
    });
  }

  build() {
    Column() {
      Text('竖屏')
        .id('HelloWorld1')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .alignRules({
          center: { anchor: '__container__', align: VerticalAlign.Center },
          middle: { anchor: '__container__', align: HorizontalAlign.Center }
        })
        .onClick(() => {
          //切换横竖屏显示模式
          win?.setPreferredOrientation(window.Orientation.PORTRAIT)
        })
      Text('横屏')
        .id('HelloWorld2')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .alignRules({
          center: { anchor: '__container__', align: VerticalAlign.Center },
          middle: { anchor: '__container__', align: HorizontalAlign.Center }
        })
        .onClick(() => {
          //切换横竖屏显示模式
          win?.setPreferredOrientation(window.Orientation.LANDSCAPE)
        })
    }
    .backgroundColor(Color.Orange)
    .height('100%')
    .width('100%')
    .justifyContent(FlexAlign.Center)
  }
}