当用户从后台回到前台，怎么开启指纹检测

onBackground(): void {
    // Ability has back to background
    hilog.info(0x0000, 'testTag', '%{public}s', '---- Ability onBackground');

    // 如何判断切后台时，时隐私空间的某个页面？
    // {"index":2,"name":"AuthPatternLockPage","path":"pages/Privacy/Auth/"}
    const routerState = router.getState()
    hilog.info(0x0000, 'testTag', '%{public}s', '---- Ability onBackground' + JSON.stringify(routerState));
    // 判断 path 路径中是否为 隐私空间 的路径
    if (routerState.path.includes('pages/Privacy')) {
      // 返回主页，自动销毁中间的页面
      router.back({
        url: 'pages/Index'
      })
    }
  }