Detect Play mode about to be entered

Question

I want to know when play mode is about to be entered.

For my case, EditorApplication.playmodeStateChanged and EditorApplication.isPlayingOrWillChangePlaymode does not work as they are called too late.

I need to check right after the scripts are recompiled so that I can prevent some reflection code in the editor from running and potentially slowing down the start of scene test. My tests revealed that the function is called while EditorApplication.isPlayingOrWillChangePlaymode is still false and the playmodeStateChanged is called even later than that.

Does anyone have a solution to this?

Answer 1

Answer by aeroson · Jun 17, 2017 at 02:48 PM

After some debugging I found out you can detect this moment with:

 EditorApplication.isPlaying = false && EditorApplication.timeSinceStartup == 0

It appears Unity internally works this way:

 EditorApplication.isPlaying = false;
 ....
 You Click Play in editor
 ....
 EditorApplication.timeSinceStartup = 0;
 Editor class OnDestroy on everything
 -> here you can detect this moment by being in OnDestroy and EditorApplication.isPlaying = false && EditorApplication.timeSinceStartup == 0
 ...
 Editor enters play mode
 EditorApplication.isPlaying = true;
 ---

I needed to find this moment in releasable (non UnityEditor script), so I did this: ApplicationState static class. Iam using it to destroy dependant components and wanted to make it work both in editor and play mode:

 public static void MyDestroy(Object obj)
 {
     if (ApplicationState.isAboutToEnterPlayMode)
         // because at this moment we cant call neither Destroy nor DestroyImmediate
         return;

     if (ApplicationState.isPlaying)
         Destroy(obj);
     else
         DestroyImmediate(obj);
 }

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Hannibal_Leo · Aug 30, 2021 at 06:44 PM 0

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Not working in 2021.1.16f1 the first Editor Update happens when Time.timeSinceLevelLoad == Time.deltaTime; which is at the first Update() call, after all Awake() and Start() Methods have been exectuted.

In my case, I am using ScriptableObject Variables, which have a "defaultValue" and a "runtimeValue" and I want to set the "runtimeValue" to "defaultValue" before entering play mode ... there seems to be no way to archive that behaviour. The solution I have right now just sets the value after Start and Awake calls, leading to all sorts of errors.

Answer 2

Answer by Ralidon · Aug 30, 2021 at 06:55 PM

Can InitializeOnLoadAttribute help you with this?

 [InitializeOnLoadAttribute]
 public static class PlayModeStateChangedExample
 {

     static PlayModeStateChangedExample()
     {
         EditorApplication.playModeStateChanged += ModeStateChanged ;
     }
 
     private static void ModeStateChanged (PlayModeStateChange state)
     {
         if (state == PlayModeStateChange.ExitingEditMode)
         {
             //do stuff
         } 
     }
 
 }

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Answer 3

Answer by McFood · May 10 at 06:04 AM

Taken from another question about changing scenes when entering playmode.

RuntimeInitializeOnLoadMethodAttribute can mark methods to run during various Unity initialization steps.

RuntimeInitializeLoadType can be set to run before a scene is loaded, or after assemblies are loaded. Either of which might work for your use case depending on when your other code is running.

 public static class DoSomething
   {
       [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType3.BeforeSceneLoad)]
        static void OnBeforeSceneLoad() { }
 
       [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterAssembliesLoaded)]
       static void OnAfterAssembliesLoaded() { }
   }

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Detect Play mode about to be entered

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