HarmonyOS 如何设置Entry页面是透明页面

import { BusinessError } from '@kit.BasicServicesKit';  
private SetUIContent(windowClass: window.Window) {  
    windowClass.setUIContent("pages/ButtonWindow",(err: BusinessError) => {  
      if (err.code) {  
        console.error(`Failed to load the content. Cause code: ${err.code}, message: ${err.message}`);  
        return;  
      }  
      console.info('Succeeded in loading the content.');  
      let color: string = '#00ff33';  
      try {  
        windowClass.setWindowBackgroundColor(color);  
      } catch (exception) {  
        console.error(`Failed to set the background color. Cause code: ${exception.code}, message: ${exception.message}`);  
      };  
    });  
}

onWindowStageCreate(windowStage: window.WindowStage): void {  
// 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;  
}  
AppStorage.setAndLink("windowStage", windowStage);// 关键代码  
hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? '');  
});  
}