DisplayCancelableProgressBar NullReferenceException

Question

I'm having trouble getting the progress bar to work. It does display and does show the progress, but it also results in a null reference exception that I can't figure out.

In my editor script during OnInspectorGUI, I'm calling this several times:

EditorUtility.DisplayProgressBar("My Task", "Operation...", progress);

At some point during execution, this error shows up:

NullReferenceException: Object reference not set to an instance of an object UnityEngine.GUIUtility.GetControlID (Int32 hint, FocusType focus) UnityEditor.InspectorWindow.OnGUI () System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr,

System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture)

Any ideas what could be wrong or what's missing? At this point I'm ready to give up and use some alternate method of showing progress.

Answer 1

Answer by watsonsong · Mar 31, 2017 at 05:20 AM

I met the same problem, when using the DisplayCancelableProgressBar. If i remove it, there is no null exception throw any more.

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Answer 2

Answer by rgrandguillot · Mar 20, 2018 at 09:58 PM

I came across the same issue after upgrading to Unity 2017.3. Before that, with Unity 5.6, DisplayCancelableProgressBar was acting perfectly with no error.

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Xarbrough · Mar 20, 2018 at 10:18 PM 1

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Have you filed a bug report for Unity? I remember having a similar issue, but forgot about it, so I doubt Unity is aware of it.

Bunny83 Xarbrough · Mar 20, 2018 at 10:41 PM 2

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I never had any problems with it. However the example shown in the documentaion doesn't make too much sense. THe DisplayCancelableProgressBar is meant to be used in a blocking execution. It's basically a modal window. If the process is started from within a OnGUI block you may want to call ExitGUI once the process has completed. So a typical usecase would be

 void OnGUI()
 {
     if (GUILayout.Button("Do heavy work"))
     {
         for(int i = 0; i < 100000; i++)
         {
             if (i%100 == 0 && EditorUtility.DisplayCancelableProgressBar("", "", (float)i/100000))
                 break;
             // do some heavy work here
             System.Thread.Sleep(10);
         }
         EditorUtility.ClearProgressBar();
         EditorGUIUtility.ExitGUI();
     }
 }

So when you press the "Do heavy work" button you basically block the main thread until your work is done. The CancelableProgressBar allows the user to interrupt that process.

rgrandguillot Bunny83 · Mar 24, 2018 at 11:36 AM 0

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Fantastic! The EditorGUIUtility.ExitGUI(); solves the problem. Thanks a lot.

DisplayCancelableProgressBar NullReferenceException

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