Today i update my system to Lion and try to update Xcode. After downloading from app store i get error.
So i remove my old Xcode 4.0 by this command
/Developer/Library/uninstall-devtools –mode=all
But now in app store i have the status "installed" and can't reinstall my Xcode. So what i must do?
p.s Trash is clear.
When I downloaded Xcode from the Mac App Store it created an Icon in launchpad called 'Install Xcode' and you're able to kick off the install from there.
My installation failed the first time and I was able to reinstall fine.
sudo /Developer/Library/uninstall-devtools –mode=all
sudo rm -rf /Developer*
sudo rm -rf /Applications/*Xcode.app
Download & Install "Install Xcode.app" or now just "Xcode.app" from the AppStore again, and run it.
Try a spotlight search for Xcode. I found an Xcode installer app in my applications folder when I did that.
Delete "Applications/Install Xcode" you can then re-install from app store
I had the same problem with other app. Deleted it and could not install again from App Store. The problem was that I had backup copy on the mounted external disk. After I have un mounted the disk with the other copy, App Store let me download the app again. Regarding to what verylastminute wrote - if Appstore can "see" any other duplication file it will not let you re-download.
I had a similar problem - clicking on Install in the Mac App Store did absolutely nothing. No error messages, no downloads, no install.
I had to all of the following to get the Xcode install to work:
rm ~/Library/Preferences/com.apple.appstore.plist
rm -r ~/Library/Saved\ Application\ State/com.apple.appstore.savedState
rm -r ~/Library/Caches/com.apple.appstore
rm -r /private/var/folders/*/*/*/com.apple.appstore
Then I deleted my existing '/Developer/Xcode.app', and an existing '/Applications/Install Xcode.app' from a previous version. Even then it didn't work until I restarted my machine!
If you have moved the Install XCode file anywhere else, and even if you have renamed it, Spotlight still shows it being in both the new location and in Applications. You need to delete any duplicates you may have made of the file before App Store will let you download it again.
open terminal window
cd /Applications
sudo rm -rf Install\ Xcode.app
After that you should be able to reinstall
I had a similar issue. I resolved it by creating another admin account on the computer. Then I installed Xcode using the new admin account.
You haven't installed Xcode, not yet. It's confusing, especially when trying to downgrade from Xcode 4.2 to Xcode 4.1 on Lion, but since the migration to App Store Xcode installs, you "install" the install app, which you then have to run to install xcode.
You've installed "/Applications/Install Xcode.app"
You need to run this to actually get "/Developer", gcc, make, etc
Simple solution : on App Store, instead of going in updates or in installed apps, simply go to "Bought apps" page. On this page, you have the option to update Xcode.
After I have tried all suggestions from this and other forums I finally managed to solve the problem in the following way: I went to the App Store menu Store -> View My Account and it was only there that I saw XCode as available with an "Install" button. Hope this helps.
来源：https://stackoverflow.com/questions/6777462/xcode-4-1-cant-reinstall-app-store-says-installed