extension UIWindow
{fileprivate class func window() -> UIWindow{
//        let window = UIApplication.shared.windows.last!  这是原来的代码let window = UIApplication.shared.keyWindow! //这是修改后的代码（亲测有效，可以正常显示）if(!window.isHidden){return window;}return (UIApplication.shared.delegate?.window!)!;}
}

参考博客：
ios11下XHToast、MBProgressHUD不显示弹框，问题解决 - csdn