Xcode 9 - simulator is not running, indexing | paused stuck

 Xcode gets stuck at Indexing Processing file, so you can see: Running on .... and Indexing | Paused, and the App doesn't launch on Simulator. Usually, this happens at the first time of running that version of the simulator. 

The solution is easy: quit from Xcode and Simulator. Launch the project again, and start to run your Application on the device again.