Android : URI is not registered (Settings | Project Settings | Schemas and DTDs)

Background

When you are developing android application you might sometime see following error on your layouts xml files in Android studio-

• URI is not registered (Settings | Project Settings | Schemas and DTDs)

Everything seems correct except this error is persistent. Gradle sync works fine too. Lets see how we can resolve this.

Solution

• Before we see how to resolve this issue make your layout file is in correct directory structure. It should be under layout folder which would be under res folder.

• Now look at build variant tab at the bottom left of android Studio. You should see the current version set. It could be -

• debug OR
• release

In my case it was release. Just switch the version and then switch it back. In my case I switched it to release and then back to debug and the error was gone.

•  If above 2 methods did not work out for you then Close all open tabs and reopen them. 
• Last but not the least - restart Android Studio.

I know these are just silly workaround. Let me know which one works for you :)