My project was operating normally until last night, when all of my tags and widgets vanished and Android suddenly generated this R class file.
below is what i have tried and nothing helps
1. Invalidate Caches/Restart...
2. Rebuild Project
3. Clean Project
4. Restart Android Studio
5. Reinstall Android Studio
Check Box Java Class
Check Box XML
Toggle Java Class
Toggle XML
![Toggle XML](https://i.stack.imgur.com/xqzmq.png)