本文主要是介绍Unity获取RootCanvas大小Rect的问题，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
今天要做一个多设备适配方案，发现在修改了Canvas Scaler的Reference Resolution后不会立即生效，RectTransfrom的大小不变。
感觉要等到Update后才执行，个人不喜欢这种控制流程。
在网上搜了半天也没发现有人问这个，因为我的某些UI要通过Rect Size来计算大小，可能比较变态吧。所以做一个笔记记录一下。
网上找到一个函数
private void OnRectTransformDimensionsChange(){Debug.Log("x==========>x:"+GetComponent<RectTransform>().rect);}
加到UI Root节点脚本中，可以在大小发生变化的时候调用到。
经过测试。在实例化UI预设的时候就已经改变了好几次大小。
AssetBundle ab = ((DownloadHandlerAssetBundle)www.downloadHandler).assetBundle;GameObject uimainobj = (GameObject)UnityEngine.Object.Instantiate(ab.LoadAsset(ab.GetAllAssetNames()[0]));//这里输出了4 次uimainobj.name = "UIMain";Canvas c = uimainobj.GetComponent<Canvas>();c.worldCamera = uiCamera; //这里输出了1次
Object.Instantiate输出了前4次。
worldCamera 赋值也会调用1次。
看了CanvasScaler.cs源码后，应该是Hander()函数重新计算了大小。
发现OnEnable函数也会调用Hander()函数，所以，我们只要禁用脚本然后打开让他调用一次就好了。
Debug.Log("x========1");cScaler.enabled = false;//不同的分辨率比率，显示不用的画布大小w_h_rate = (float)Screen.width / Screen.height;isPad = w_h_rate > pad_rate ? true : false;if (isPad)cScaler.referenceResolution = new Vector2(padUIWidth, padUIHeight);elsecScaler.referenceResolution = new Vector2(defaultUIWidth, defaultUIHeight);cScaler.enabled = true;Debug.Log("x========2");
2133就是正常后的高度，看来可行。
附：CanvasScaler.cs 部分代码
protected override void OnEnable(){base.OnEnable();this.m_Canvas = this.GetComponent<Canvas>();this.Handle();}/// <summary>/// <para>See MonoBehaviour.OnDisable.</para>/// </summary>protected override void OnDisable(){this.SetScaleFactor(1f);this.SetReferencePixelsPerUnit(100f);base.OnDisable();}/// <summary>/// <para>Handles per-frame checking if the canvas scaling needs to be updated.</para>/// </summary>protected virtual void Update(){this.Handle();}/// <summary>/// <para>Method that handles calculations of canvas scaling.</para>/// </summary>protected virtual void Handle(){if ((UnityEngine.Object) this.m_Canvas == (UnityEngine.Object) null || !this.m_Canvas.isRootCanvas)return;if (this.m_Canvas.renderMode == RenderMode.WorldSpace){this.HandleWorldCanvas();}else{switch (this.m_UiScaleMode){case CanvasScaler.ScaleMode.ConstantPixelSize:this.HandleConstantPixelSize();break;case CanvasScaler.ScaleMode.ScaleWithScreenSize:this.HandleScaleWithScreenSize();break;case CanvasScaler.ScaleMode.ConstantPhysicalSize:this.HandleConstantPhysicalSize();break;}}}/// <summary>/// <para>Handles canvas scaling that scales with the screen size.</para>/// </summary>protected virtual void HandleScaleWithScreenSize(){Vector2 vector2 = new Vector2((float) Screen.width, (float) Screen.height);float scaleFactor = 0.0f;switch (this.m_ScreenMatchMode){case CanvasScaler.ScreenMatchMode.MatchWidthOrHeight:scaleFactor = Mathf.Pow(2f, Mathf.Lerp(Mathf.Log(vector2.x / this.m_ReferenceResolution.x, 2f), Mathf.Log(vector2.y / this.m_ReferenceResolution.y, 2f), this.m_MatchWidthOrHeight));break;case CanvasScaler.ScreenMatchMode.Expand:scaleFactor = Mathf.Min(vector2.x / this.m_ReferenceResolution.x, vector2.y / this.m_ReferenceResolution.y);break;case CanvasScaler.ScreenMatchMode.Shrink:scaleFactor = Mathf.Max(vector2.x / this.m_ReferenceResolution.x, vector2.y / this.m_ReferenceResolution.y);break;}this.SetScaleFactor(scaleFactor);this.SetReferencePixelsPerUnit(this.m_ReferencePixelsPerUnit);}
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