词法或预处理器问题出错(UIKit/UIKit)。h文件未找到)

I've read the other question in regards to lexical and preprocessor issues and I've tried to use what helped solve their problems. Unfortunately, none of those solutions have helped rectify the problem. This error came out of nowhere and I'm not sure what I can do, other than what read, to fix this. Please help!I've read the other question in regards to lexi