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"SetActive can only be called from the main thread"

Discussion in 'Windows' started by K1kk0z90_Unity, Feb 18, 2015.

  1. K1kk0z90_Unity

    K1kk0z90_Unity

    Joined:
    Jun 2, 2013
    Posts:
    90
    Hi all!
    I'm trying to port my Unity game to Windows Store. Sometimes, running the Visual Studio project generated by Unity, the game crashes with the following error:
    This error raises just sometimes, while other times the game runs without crashing. Here is the piece of code that raises the exception:
    Code (CSharp):
    1. #if NETFX_CORE
    2.     async
    3. #endif
    4.     public void Foo()
    5.     {
    6.         ...
    7. #if !NETFX_CORE
    8.         if (Bar())
    9. #else
    10.         if (await Bar())
    11. #endif
    12.         {
    13.             myGameObject.SetActive(true); // THIS INSTRUCTION RAISES THE EXCEPTION
    14.         }
    15.  
    16.         ...
    17.     }
    It seems to me that the problem is that sometimes the "myGameObject.SetActive(true)" instruction is executed into another thread, but I don't understand how it can happen.
    What's wrong with my code?
    Thank you in advance for your help!
     
    K1kk0z90_Unity, Feb 18, 2015
    #1

  2. Tomas1856

    Tomas1856

    Unity Technologies

    Joined:
    Sep 21, 2012
    Posts:
    3,918
    As the error says you're calling "myGameObject.SetActive(true); " from the wrong thread, to fix this you must use InvokeOnAppThread, something like this:
    Code (csharp):
    1.  
    2. WSAApplication.InvokeOnAppThread(()=>
    3. {
    4.    myGameObject.SetActive(true);
    5. }
    6.  
     
    Tomas1856, Feb 18, 2015
    #2
    ZoraMikau and K1kk0z90_Unity like this.

  3. Tautvydas-Zilys

    Tautvydas-Zilys

    Unity Technologies

    Joined:
    Jul 25, 2013
    Posts:
    10,680
    await transfers control to another thread.
     
    Tautvydas-Zilys, Feb 18, 2015
    #3
    K1kk0z90_Unity likes this.

  4. K1kk0z90_Unity

    K1kk0z90_Unity

    Joined:
    Jun 2, 2013
    Posts:
    90
    Thank you both for your answers! :)
    So, if I understood correctly, inside an async method every UnityEngine's method call must be wrapped into InvokeOnAppThread()?
     
    K1kk0z90_Unity, Feb 18, 2015
    #4
    Simic13 likes this.

  5. Tomas1856

    Tomas1856

    Unity Technologies

    Joined:
    Sep 21, 2012
    Posts:
    3,918
    Yes, because most of the UnityEngine API is not thread-safe, so you must call them in the correct thread - also known as app thread in this case.
     
    Tomas1856, Feb 18, 2015
    #5
    Simic13 and K1kk0z90_Unity like this.

  6. K1kk0z90_Unity

    K1kk0z90_Unity

    Joined:
    Jun 2, 2013
    Posts:
    90
    Ok, good to know. Thank you very much for your precious help! :)
     
    K1kk0z90_Unity, Feb 18, 2015
    #6