When I try to run the Xcode simulator I get the error 'Stop “(null)”?'

Question

I just updated to Xcode 7 and ran an app on a live device. Now for some reason, I get an error when I try to run an app in a simulator.

Stop “(null)”?  An instance of “(null)” is already running. Choose “Stop” to terminate and launch a new instance. 

When I press the stop button it grays out, as in the screen shot, but nothing happens. I have tried resetting the content and settings on the simulator, but that didn't help.

Answer 1

Getting this as well with Xcode 7.

I've been following these simple steps to avoid seeing the error:

1. Build your app.
2. Run your app.

Annoying, and not a solution, but I think this is a bug within Xcode 7.

Answer 2

Completely quitting Xcode 7 and reloading resolved the simulator is already running it for me.