Problem With Application Focus Change on Hololens

I have the following problem with the Vuforia image tracking on the Hololens:

Vuforia Version: 7.5.26 Unity Version: 2018.2.17

• Start an application with an image tracking
• image tracking works
• Use the bloom gesture and select "Mixed Reality Home" to put the application in the background
• Click the application window again
• image tracking does not work anymore

I cannot reproduce the same behaviour on the unity editor.

Workaround: Disable the vuforia behaviour on focus lost and enable it again on focus with a delay.

This seems like a bug to me.

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using System.Collections; using UnityEngine; using Vuforia; /* * Script to disable Vuforia components on application focus lost and re-enable delayed on application focus, * because tracking does not work anymore on Hololens after an application focus change. */ public class VuforiaAppFocusHandling : MonoBehaviour { [SerializeField] public GameObject ArCamera;

private void OnApplicationFocus(bool hasFocus) {   Debug.Log(hasFocus ? "Application has Focus" : "Application does not have focus");   EnableTracking(hasFocus); }

public void EnableTracking(bool track) {   if (track)   {    StartCoroutine(DelayedEnable(true));   }   else   {    EnableVuforiaComponents(false);   } }

private IEnumerator DelayedEnable(bool track) {   yield return new WaitForSeconds(0.5f);   EnableVuforiaComponents(track); }

private void EnableVuforiaComponents(bool track) {   ArCamera.GetComponent<VuforiaBehaviour>().enabled = track;   ArCamera.GetComponent<DefaultInitializationErrorHandler>().enabled = track; }

}