HarmonyOS 禁止登录页面截屏：window.findWindow("test")问题

示例代码：

let isPrivacyMode: boolean = true;
let windowClass: window.Window = window.findWindow("test");
let promise = windowClass.setWindowPrivacyMode(isPrivacyMode); // 设置防截屏录屏
promise.then(() => {
  console.info('Succeeded in setting the window to privacy mode.');
}).catch((err: BusinessError) => {
  console.error(`ErrorCode: ${err.code},  Message: ${err.message}`);
})

问题：

let windowClass: window.Window = window.findWindow("test");

这行代码报错，应该是找不到 'test'的window，需要在哪里设置什么吗