我的需求是APP大部分是竖屏显示，在某个页面需要显示横屏。

直接上答案

1、在EntryAbility中获取globalThis.windowClass

  onWindowStageCreate(windowStage: window.WindowStage) {
    // Main window is created, set main page for this ability
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');

    windowStage.getMainWindow((err, data) => {
      if (err.code) {
        console.error('Failed to obtain the main window. Cause: ' + JSON.stringify(err));
        return;
      }
      //保存globalThis.windowClass
      globalThis.windowClass = data
      console.info('Succeeded in obtaining the main window. Data: ' + JSON.stringify(data));
    });

    windowStage.loadContent('pages/BarrageTabPage', (err, data) => {
      if (err.code) {
        hilog.error(0x0000, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err) ?? '');
        return;
      }
      hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? '');
    });
  }

2、在需要横屏显示的页面中添加

//设置该页面为横屏
  aboutToAppear() {
    globalThis.windowClass.setPreferredOrientation(window.Orientation.LANDSCAPE)
  }

3、返回到竖屏显示的页面，需要在竖屏页面添加

  onPageShow() {
    globalThis.windowClass.setPreferredOrientation(window.Orientation.PORTRAIT)
  }

这三步即可设置部分页面横屏