iOS emulator is installed but Xcode cannot be displayed

The system has recently been re-installed, and then use time machine to restore to the original state, everything is OK, but when using Xcode found a simulator is not:

All kinds of tossing, reloading SDK Ah, re-install Xcode Ah, finally found that if your simulator ( /Applications/Xcode/Contents/Developer/Applications/iOS Simulator ) and the SDK ( /Applications/Xcode/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs ) to determine the circumstances, do not think about the various reloading.

At the same time, in this case, you go to run the simulator alone, you will get the following error: "Unable to determine device", this error, in all normal circumstances, is open multiple simulator. In the case we met today, there is not a simulator !

Solve:

1. Open Developer Tool---IOS simulator (even if you don't see the emulator at this point, but the program is actually open, the tray icon and menu are evidence)
2. Find menu hardware, Device-Manage Devices
3. Next, add the emulator.

By this, the simulator finally appeared, really tangled.

iOS emulator is installed but Xcode cannot be displayed