URI is not registered ( Setting | Project Settings | Schemas and DTDs ) 解决方案

问题出现描述：

For me this was because I was using a debug and release build variant. I added the new folders src/debug/res/layout/some_layout.xml file manually, and it didn't recognize the URI. 

使用build variant的时候在src建了和main同级的目录，然后res/layout下面拷贝了一个main下面正常的布局文件。然后就在

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1. <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
2.     xmlns:tools="http://schemas.android.com/tools"  

上面两行报错了:

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1. URI is not registered ( Setting | Project Settings | Schemas and DTDs )  

解决方案：

1.I switched the build variant to release, and then back to debug. This caused AS to reload something, and the error went away.这个方案没试验过

2.浏览statckoverflow其他页面的时候有人说是这版本的bug，建议升级。我升级之后重启as问题就解决了。不过我感觉具体原因应该是第一种方案说的as现在有bug，没有reload一些资源造成的。

http://stackoverflow.com/questions/16883427/why-is-android-studio-reporting-uri-is-not-registered