Unity3D研究院之Prefab里面的Prefab关联问题

最近在做UI部分中遇到了这样的问题，就是Prefab里面预制了Prefab。可是在Unity里面一旦Prefab预制了Prefab那么内部的Prefab就失去关联。导致与如果要改内部的Prefab需要把所有引用的地方全部改一遍。今天在逛国外网站看到了一个老外的思路，原文在这里 http://framebunker.com/blog/poor-mans-nested-prefabs/
下面直接上代码

using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;
using UnityEditor.Callbacks;
#endif
using System.Collections.Generic;
 
[ExecuteInEditMode]
public class PrefabInstance : MonoBehaviour
{
    public GameObject prefab;
 
#if UNITY_EDITOR    
    // Struct of all components. Used for edit-time visualization and gizmo drawing
    public struct Thingy {
        public Mesh mesh;
        public Matrix4x4 matrix;
        public List<Material> materials;
    }
 
    [System.NonSerializedAttribute] public List<Thingy> things = new List<Thingy> ();
 
    void OnValidate () {
        things.Clear();
        if (enabled)
            Rebuild (prefab, Matrix4x4.identity);
    }
 
    void OnEnable () {
        things.Clear();
        if (enabled)
            Rebuild (prefab, Matrix4x4.identity);
    }
 
    void Rebuild (GameObject source, Matrix4x4 inMatrix) {
        if (!source)
            return;
 
        Matrix4x4 baseMat = inMatrix * Matrix4x4.TRS (-source.transform.position, Quaternion.identity, Vector3.one);
        
        foreach (MeshRenderer mr in source.GetComponentsInChildren(typeof (Renderer), true))
        {
            things.Add(new Thingy () {
                mesh = mr.GetComponent<MeshFilter>().sharedMesh,
                matrix = baseMat * mr.transform.localToWorldMatrix,
                materials = new List<Material> (mr.sharedMaterials)
            });
        }
 
        foreach (PrefabInstance pi in source.GetComponentsInChildren(typeof (PrefabInstance), true))
        {
            if (pi.enabled && pi.gameObject.activeSelf)
                Rebuild (pi.prefab, baseMat * pi.transform.localToWorldMatrix);
        }        
    }
 
    // Editor-time-only update: Draw the meshes so we can see the objects in the scene view
    void Update () {
        if (EditorApplication.isPlaying)
            return;
        Matrix4x4 mat = transform.localToWorldMatrix;
        foreach (Thingy t in things)
            for (int i = 0; i < t.materials.Count; i++)
                Graphics.DrawMesh (t.mesh, mat * t.matrix, t.materials[i], gameObject.layer, null, i);
    }
 
    // Picking logic: Since we don't have gizmos.drawmesh, draw a bounding cube around each thingy
    void OnDrawGizmos () { DrawGizmos (new Color (0,0,0,0)); }
    void OnDrawGizmosSelected () { DrawGizmos (new Color (0,0,1,.2f)); }
    void DrawGizmos (Color col) {
        if (EditorApplication.isPlaying)
            return;
        Gizmos.color = col;
        Matrix4x4 mat = transform.localToWorldMatrix;
        foreach (Thingy t in things)
        {
            Gizmos.matrix = mat * t.matrix;
            Gizmos.DrawCube(t.mesh.bounds.center, t.mesh.bounds.size);
        }        
    }
 
    // Baking stuff: Copy in all the referenced objects into the scene on play or build
    [PostProcessScene(-2)]
    public static void OnPostprocessScene() { 
        foreach (PrefabInstance pi in UnityEngine.Object.FindObjectsOfType (typeof (PrefabInstance)))
            BakeInstance (pi);
    }
 
    public static void BakeInstance (PrefabInstance pi) {
        if(!pi.prefab || !pi.enabled)
            return;
        pi.enabled = false;
        GameObject go = PrefabUtility.InstantiatePrefab(pi.prefab) as GameObject;
        Quaternion rot = go.transform.localRotation;
        Vector3 scale = go.transform.localScale;
        go.transform.parent = pi.transform;
        go.transform.localPosition = Vector3.zero;
        go.transform.localScale = scale;
        go.transform.localRotation = rot;
        pi.prefab = null;
        foreach (PrefabInstance childPi in go.GetComponentsInChildren<PrefabInstance>())
            BakeInstance (childPi);
    }
 
#endif
}

用法比较简单，比如我有两个Prefab，inside嵌入在Big里面。如下图所示，把PrefabInstance脚本挂在Big上，然后把inside拖入下方。

 

OK 无论怎么修改inside这个Prefab，当实例化Big的时候都能得到最新修改的Inside这个Prefab。

持续思考：

界面预览问题，就是我在布界面的时候，我需要把子集Prefab界面控件拖进来预览效果。如果用上述思路UI的Prefab就必须通过脚本自动生成。一份是预览用的也就是不需要脚本的，一份是只带脚本运行时动态生成的。在处理自动生成UIPrefab的时候可以利用tag 比如像这种需要内嵌的Prefab标记一个特殊的tag，在Editor下完成Prefab的导出。另外布界面的时候不需要绑定脚本，而上述脚本的绑定也应该由Editor导出Prefab的时候完成。

总之一切布界面的时候只操作Prefab不操作脚本。