This has now happened several times with the frequent updates to Mac OS and Catalina in particular. The problem is that even though you close everything before the upgrade and then you launch Xcode after the upgrade completes – Xcode will not launch correctly.
When you start xcode for the first time after the update – xcode “hangs” with the spinning activity indication and does not start correctly. Rebooting the laptop does not help. This is annoying to say the least.
So to resolve this you need to know the user that you are logging on with – in this case lets use Hal as an exampleIn finder you will need to force quit the unresponsive xcode.
Then open the harddrive of your laptop or mac.
In order to see the hidden folders use command + shift + full stop (you can toggle it back to normal when xcode loads)
Now in the hal users folder – scroll down until you see the greyed Library folder
Scroll down until you see the Saved Application State folder within that – expand it if its not already
Locate the com.apple.dt.Xcode.savedState entry – then right click to rename or put it in the bin
Now start Xcode and confirm that you can see previous projects and create new projects.
Finally return to finder and use command + shift + full stop