HarmonyOS UIContext获取

loadcontent和getMainWindow两个接口是异步的，getUIContext是同步接口。loadcontent和getMainWindow会同时执行但是回调时序不保证，就会有先getMainWindow拿到结果，但此时content没有完成加载的情况。loadcontent和getMainWindow两个接口是异步的,最好是再Loadcontent的回调中调用接口。保证时序。推荐示例：

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

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

    windowStage.getMainWindow((err: BusinessError, data) => {
      let errCode: number = err.code;
      if (errCode) {
        console.error('Failed to obtain the main window.Cause:' + JSON.stringify(err))
      }
      let uiContext = data.getUIContext();
      console.log(JSON.stringify(uiContext))
    })
    hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? '');
  });
}