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Question by JYKeith · May 24, 2017 at 07:38 AM · addcomponent

Strange AddComponent behaviour?

I really don't know what is wrong with my code.

I'm adding unity Image component to new sibling gameobject from OnEnable.

It's simple (this is sample code)

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.EventSystems;
 using UnityEngine.UI;
 
 public class Test : UIBehaviour
 {
     public GameObject parent;
 
     private GameObject modalBackground;
     protected override void OnEnable()
     {
         base.OnEnable();
 
         if (null != modalBackground)
         {
             Destroy(modalBackground);
             modalBackground = null;
         }
 
         modalBackground = new GameObject("UI Modal Background");
         
         modalBackground.GetComponent<Transform>().SetParent(parent.GetComponent<Transform>(), false);
         modalBackground.transform.SetSiblingIndex(transform.GetSiblingIndex());
         modalBackground.SetActive(true);
 
         var image = modalBackground.AddComponent<Image>();
         image.fillCenter = true;
         image.color = new Color(0f, 0f, 0f, 0.3f);
         var rectTransform = modalBackground.transform as RectTransform;
         rectTransform.anchorMax = new Vector2(1.0f, 1.0f);
         rectTransform.anchorMin = new Vector2(0.0f, 0.0f);
     }
 }
   

alt text

var image = modalBackground.AddComponent Image ();

When call 'AddComponent' here, Unity calls Test::OnEnable again. And I think it creates new Test instance because modalBackground is null as it calls again. So it's infinite recursive call and it doen't make sense. Can you find something wrong here?

Call stack while recursive calling

alt text

Environment : windows 10, Unity 5.6.1f1

st.png (20.6 kB)
callstack.png (15.0 kB)
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Answer by ufengle · Sep 14, 2017 at 08:57 AM

,同样的unity版本,我也遇到的类似的情况,只要有把Transform变成RectTransform的操作,就会调用OnEnable ,且调用的不仅仅是自身(gameObject)的,还会触发parent的。而我用4.7版本,却不会出现这个情况,不清楚这是不是BUG。

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