Why does Android Studio highlight “Theme” red in styles.xml?

Question

Red highlight means Cannot resolve symbol \'Theme\'

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Answer 1

I had added appcompatv7 project as a module but I have forgotten to show it to my application module. Just I have realized and fixed. Now it doesn't alert me anymore. Thanks for your reply, tritop.

Answer 2

It's very weird but I had the dependency in my .gradle.

To solve the issue I deleted it(//commented), sync, get all error because of it, put the dependency again, sync again. Then the problem was gone!

Answer 3

Only this worked for me!

• Close project (File> Close Project)
• Import / Re-Open project again (NOT from Recent)

Error should be resolved now.

If that did not resolve, then try below

• Open build.gradle, remove appcompact-v7 dependency line and sync.
• Again add appcompact-v7 dependency and sync.

Issue must be resolved!

Answer 4

Just delete the dependencies below and sync. Paste them again and sync.

implementation 'com.android.support:design:28.0.0'
implementation 'com.android.support:appcompat-v7:28.0.0'

Answer 5

This is how I solved it:

1. Go to your project directory (or to Project View)
2. Go into the .idea directory
3. Remove caches and libraries directories
4. File -> Invalidate Caches / Restart

Should be OK now.