IDEA之"URI is not registered (Settings | Languages & Frameworks | Schemas and DTDs)"5s解决办法

错误描述

 

解决办法

复制报红的URL ==> 右击"File" ==> "Settings..." ==> "Language & Frameworks" ==> "Schemas and DTDs" ==> 点右边下侧的"+" ==> 粘贴输入URL ==> 变绿成功解决。