URL is not registered (Settings | Languages & Frameworks | Schemas and DTDs)

File - Settings - Schemas and DTDS时,选中报错的地址,然后Ctrl+alt+s打开设置(或者右键 -> setting)找到
把报错的地址填入就可以了,最后应用一下

原文地址:https://www.cnblogs.com/z0909y/p/10751925.html