Can't start Xcode - stuck on installing state

I was trying to upgrade Xcode because it didn't let me upload to apps to iTunes Connect.

Now it's stuck in installing state (few hours) and doesn't start:

Xcode is being updated
Xcode can not be opened while it is being updated.

What do to?

There is a small progress bar under the Launchpad icon in the Menu Bar.

You can also see the current download progress by hovering over the icon.

Wait for it to end.

In the Updates tab of the Apple App Store, after waiting 1 hour for "2 minutes left," I hit CMD+R to refresh and that seemed to "jump start" it. It finished within 60s after that. Could have been coincidence though (YMMV).

Update: This answer doesn't work anymore as of Big Sur because there is no Check for Unfinished Downloads option.

original obsolete answer Try this: enter the App Store, click on Store in the top-left menu and select Check for Unfinished Downloads. Enter your Apple ID and password.

The above has worked for me on MacOS Sierra, I suspect that XCode was stuck waiting for credentials before download.

Update: Check for Unfinished Downloads option may not be present in the later versions of macOS.

In launch pad hold the Xcode icon until the X appears and click the X to delete Xcode then go back to the app store and get a fresh copy.