Files in Xcode not working (names in red)

I renamed my app folder to try and change the name of the app because it didn't work in the project navigator and when I did so, all files came up in red. I have tried to fix it by renaming the files back to how they were but it still doesn't work.

Any help would be greatly appreciated.

Link to dropbox: https://www.dropbox.com/s/omvo0saff0z9ncc/TicketekApp%202.zip?dl=0

Solution

If files marked in red, they are "not found" by Xcode.

You either moved or deleted them within File Finder, outside Xcode. Delete the red marked files within XCode, then add them again to XCode.

This will solve your problem.