The iOS 13.0 simulator runtime is not available

I installed the Xcode-11-beta along with macOS 10.15 beta. At first I can play with SwiftUI preview normally. But after I tried to move the Xcode-beta from the ~/Downloads directory where I initially installed it, to /Applications, the preview can't work. Here is the error:

So I moved it back to ~/Downloads, hoping things will go well as before. But it gives the same error.

After this, I reinstalled it and I still got this error. Can anyone help me fix it?

The content of diagnostics report is this:

== DATE:

Wednesday, June 5, 2019 at 10:25:46 PM China Standard Time



== PENDING U

    PDATE REASONS:





== PREVIEW UPDATE ERROR:

    unexpected error occurred

    Error Domain=com.apple.CoreSimulator.SimError Code=161 "The iOS 13.0 simulator runtime is not available." UserInfo={NSLocalizedRecoverySuggestion=Download the iOS 13.0 simulator runtime from the Components section in Xcode's Preferences., NSLocalizedFailureReason=runtime path not found, NSLocalizedDescription=The iOS 13.0 simulator runtime is not available.}



== VERSION INFO:

    Tools: 11M336w

    OS:    19A471t



== ENVIRONMENT:

    [x] In valid workspace
    [x] Project is using the new build system
        Previews are available for targets that are built with the new build system. Change your project to use the new build system.
    [x] Selected scheme (Landmarks)
        Select a scheme from the scheme picker in the toolbar
    [x] Selected run destination (iPhone 8)
        Select a run destination from the scheme picker in the toolbar
    [x] Have workspace arena
        Try quitting and reopening your workspace
    [x] Have build arena
        Try quitting and reopening your workspace
    [x] Open file has supported build settings

Weird thing is I wake up in the morning and start my computer, the Canvas and the iOS 13.0 Simulator can work now.

So, I guess the solution to this may be just a brutal restart. ;]