求告知如何实现防截屏功能

import { window } from '@kit.ArkUI'; 
import { BusinessError } from '@kit.BasicServicesKit'; 
 
@Entry 
@Component 
struct Index20 { 
  @State message: string = 'Hello World'; 
  window?: window.Window; 
 
  aboutToAppear(): void { 
    window.getLastWindow(getContext(this)).then((mainWindow) => { 
      this.setWindowPrivacyMode(mainWindow, true) 
    }).catch((error: ESObject) => { 
      console.log("getMainWindow error: " + JSON.stringify(error)) 
    }) 
  } 
 
  setWindowPrivacyMode(windowClass: window.Window, isPrivacyMode: boolean) { 
    try { 
      // 设置窗口为隐私模式，窗口内容将无法被截屏或录屏。 
      let promise = windowClass.setWindowPrivacyMode(isPrivacyMode); 
      promise.then(() => { 
        console.info('Succeeded in setting the window to privacy mode.'); 
      }).catch((err: BusinessError) => { 
        console.error('Failed to set the window to privacy mode. Cause: ' + JSON.stringify(err)); 
      }); 
 
      console.info(`setWindowPrivacyMode 已执行`); 
    } catch (exception) { 
      console.error('Failed to set the window to the privacy mode. Cause:' + JSON.stringify(exception)); 
    } 
  } 
 
  build() { 
    Column() { 
      Text(this.message) 
        .id('Index20HelloWorld') 
        .fontSize(50) 
        .fontWeight(FontWeight.Bold) 
        .alignRules({ 
          center: { anchor: '__container__', align: VerticalAlign.Center }, 
          middle: { anchor: '__container__', align: HorizontalAlign.Center } 
        }) 
    } 
    .height('100%') 
    .width('100%') 
  } 
}