Android Studio layout Error : Unknown attribute

Question

Android Studio Code Completion seems not working on xml and also it doesn\'t recognize any xml attribute except the attrs on Android support v7 views. Screenshot:

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Answer 1

If you are Android Studio then go to tools and then Android then click on build with gradle, it will solve the error. I encountered it too.

Tools->Android->Build with Gradle

Answer 2

I had this issue for a while and tried all the "solutions" provided;

• Sync Gradle files.
• Invalidate cache.
• Removed and re-add project.
• Reinstall Android Studio.

Nothing worked, until I came across this answer (by 4gus71n) which has worked for me every time this rather rare, but annoying issue has presented itself: https://stackoverflow.com/a/53160674/5692877

In my case I;

1. Closed Android Studio.
2. Cleared the contents of the C:\Users\MyUsername\.AndroidStudio3.2\system\caches\ directory.
3. Relaunched Android Studio.

Worked a treat!