About XCODE interface problems

xcode only shows part of the code, the other full disappeared

Originally part of a complete xcode code in the middle, on the left is the default file manager now they are gone, and now looks like the file manager, double click to open the code file out of the same small box.
Reply:
Menu, view where to find
Reply:
The upper left corner and the middle of the place of their choice, right view mode