HarmonyOS 子窗口设置背景颜色不生效的问题

import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let windowStage_: window.WindowStage | null = null;
let sub_windowClass: window.Window | null = null;
export default class EntryAbility extends UIAbility {
  showSubWindow() {
    // 1.创建应用子窗口。
    if (windowStage_ == null) {
      console.error('Failed to create the subwindow. Cause: windowStage_ is null');
    }
    else {
      windowStage_.createSubWindow("mySubWindow", (err: BusinessError, data) => {
        let errCode: number = err.code;
        if (errCode) {
          console.error('Failed to create the subwindow. Cause: ' + JSON.stringify(err));
          return;
        }
        sub_windowClass = data;
        console.info('Succeeded in creating the subwindow. Data: ' + JSON.stringify(data));
        // 2.子窗口创建成功后，设置子窗口的位置、大小及相关属性等。
        sub_windowClass.moveWindowTo(300, 300, (err: BusinessError) => {
          let errCode: number = err.code;
          if (errCode) {
            console.error('Failed to move the window. Cause:' + JSON.stringify(err));
            return;
          }
          console.info('Succeeded in moving the window.');
        });
        sub_windowClass.resize(500, 500, (err: BusinessError) => {
          let errCode: number = err.code;
          if (errCode) {
            console.error('Failed to change the window size. Cause:' + JSON.stringify(err));
            return;
          }
          console.info('Succeeded in changing the window size.');
        });
        // 3.为子窗口加载对应的目标页面。
        sub_windowClass.setUIContent("pages/Page3", (err: BusinessError) => {
          sub_windowClass?.setWindowBackgroundColor("#00000000")
          let errCode: number = err.code;
          if (errCode) {
            console.error('Failed to load the content. Cause:' + JSON.stringify(err));
            return;
          }
          console.info('Succeeded in loading the content.');
          // 3.显示子窗口。
          (sub_windowClass as window.Window).showWindow((err: BusinessError) => {
            let errCode: number = err.code;
            if (errCode) {
              console.error('Failed to show the window. Cause: ' + JSON.stringify(err));
              return;
            }
            console.info('Succeeded in showing the window.');
          });
        });
      })
    }
  }

  destroySubWindow() {
    // 4.销毁子窗口。当不再需要子窗口时，可根据具体实现逻辑，使用destroy对其进行销毁。
    (sub_windowClass as window.Window).destroyWindow((err: BusinessError) => {
      let errCode: number = err.code;
      if (errCode) {
        console.error('Failed to destroy the window. Cause: ' + JSON.stringify(err));
        return;
      }
      console.info('Succeeded in destroying the window.');
    });
  }

  onWindowStageCreate(windowStage: window.WindowStage) {
    windowStage_ = windowStage;
    windowStage.loadContent("pages/Page2", (err: BusinessError) => {
      let errCode: number = err.code;
      if (errCode) {
        console.error('Failed to load the content. Cause:' + JSON.stringify(err));
        return;
      }
      console.info('Succeeded in loading the content.');
    });
    // 可以在适当的时机，如主窗口上按钮点击事件等，创建子窗口。并不一定需要在onWindowStageCreate调用，这里仅作展示
    this.showSubWindow();
  }

  onWindowStageDestroy() {
    // 可以在适当的时机，如子窗口上点击关闭按钮等，销毁子窗口。并不一定需要在onWindowStageDestroy调用，这里仅作展示
    this.destroySubWindow();
  }
};