unity3d Resources.Load動態加載資源

　　初步整理並且學習unity3d資源加載方法，預計用時兩天完成入門學習Unity3d常用兩種加載資源方案：Resources.Load和AssetBundle

Resources.Load就是從一個缺省打進程序包里的AssetBundle里加載資源而一般AssetBundle文件需要你自己創建，運行時動態加載，

可以指定路徑和來源的。其實場景里所有靜態的對象也有這么一個加載過程，只是Unity后台替你自動完成

一：Resources.Load：使用這種方式加載資源，首先需要下Asset目錄下創建一個名為Resources的文件夾，這個命名是U3D規定的方式，然后把資源文件放進去，

當然也可以在Resources中再創建子文件夾，當然在代碼加載時需要添加相應的資源路徑，下面是一個簡demo，兩個預設，Cube和Sphere，

其中Cube放在Resource中的Prebs中，而Sphere放在Resources跟目錄下，下面分別實現Resources.Load資源的加載

 

using UnityEngine;
using System.Collections;

public class LoadResDemo : MonoBehaviour {

    private string cubePath = "Prebs/MyCubePreb";
    private string spherePath = "MySpherePreb";
    void Start () {
        //把資源加載到內存中
        Object  cubePreb = Resources.Load(cubePath, typeof(GameObject));
        //用加載得到的資源對象，實例化游戲對象，實現游戲物體的動態加載
        GameObject cube = Instantiate(cubePreb) as GameObject;



        //以下同理實現Sphere的動態實例化
        //把資源加載到內存中
        Object spherePreb = Resources.Load(spherePath, typeof(GameObject));
        //用加載得到的資源對象，實例化游戲對象，實現游戲物體的動態加載
        GameObject sphere = Instantiate(spherePreb) as GameObject;
    }
    
    void Update () {
    
    }
}

　　將上面的腳本附加到某個游戲對象上，在運行游戲時就可以看到場景中動態創建的上面的游戲對象了

上面是第一種使用Resources.Load()的方式動態加載游戲對象的，然而在項目中更長用的卻是第二種使用AssetBundle的方式動態加載游戲對象。

使用AssetBundle打包預設或者場景可以將與其相關的所有資源打包，這樣很好地解決資源的依賴問題，使得我們可以方便的加載GameObject

首先需要打包資源：

using UnityEngine;
using System.Collections;
using UnityEditor;
using System.IO;
public class AesstBundleTest : MonoBehaviour {



    [MenuItem("Custom Bundle/Create Bundel Main")]
    public static void creatBundleMain()
    {
        //獲取選擇的對象的路徑
        Object[] os = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
        bool isExist = Directory.Exists(Application.dataPath + "/StreamingAssets");
        if (!isExist)
        {
            Directory.CreateDirectory(Application.dataPath + "/StreamingAssets");
        }
        foreach (Object o in os)
        {
            string sourcePath = AssetDatabase.GetAssetPath(o);

            string targetPath = Application.dataPath + "/StreamingAssets/" + o.name + ".assetbundle";
            if (BuildPipeline.BuildAssetBundle(o, null, targetPath, BuildAssetBundleOptions.CollectDependencies))
            {
                print("create bundle cuccess!");
            }
            else
            {
                print("failure happen");
            }
            AssetDatabase.Refresh();
        }
    }
    [MenuItem("Custom Bundle/Create Bundle All")]
    public static void CreateBundleAll()
    {
        bool isExist = Directory.Exists(Application.dataPath + "/StreamingAssets");
        if (!isExist)
        {
            Directory.CreateDirectory(Application.dataPath + "/StreamingAssets");
        }
        Object[] os = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
        if (os == null || os.Length == 0)
        {
            return;
        }
        string targetPath = Application.dataPath + "/StreamingAssets/" + "All.assetbundle";
        if (BuildPipeline.BuildAssetBundle(null, os, targetPath, BuildAssetBundleOptions.CollectDependencies))
        {
            print("create bundle all cuccess");
        }
        else
        {
            print("failure happen");
        }
        AssetDatabase.Refresh();
    }

}

把上面的代碼放在Editor中，在菜單欄中就可以看見自定的菜單項，選中需要打包的預設，就可以把對應的預設打包並輸出到StreamAssets中了

然后是動態加載資源：

using UnityEngine;
using System.Collections;

public class LoadBundleTest : MonoBehaviour {
    //不同平台下StreamingAssets的路徑是不同的，這里需要注意一下。
    public static readonly string PathURL =
    #if UNITY_ANDROID
        "jar:file://" + Application.dataPath + "!/assets/";
    #elif UNITY_IPHONE
        Application.dataPath + "/Raw/";
    #elif UNITY_STANDALONE_WIN || UNITY_EDITOR
    "file://" + Application.dataPath + "/StreamingAssets/";
    #else
        string.Empty;
    #endif



    
    // Update is called once per frame
    void Update () {
    
    }

    void OnGUI()
    {
        if (GUILayout.Button("Load Bundle Main"))
        {
            string path_shpere = PathURL + "MySpherePreb.assetbundle";
            StartCoroutine(loadBundleMain(path_shpere));

            string path_cube = PathURL + "MyCubePreb.assetbundle";
            StartCoroutine(loadBundleMain(path_cube));
            print(path_cube);
        }

        if (GUILayout.Button("Load Bundle All"))
        {
            StartCoroutine(loadBundleAll(PathURL + "All.assetbundle"));
        }
    }


    private IEnumerator loadBundleMain(string path)
    {
        WWW bundle = new WWW(path);
      //  yield return bundle;
         Instantiate(bundle.assetBundle.mainAsset);
         bundle.assetBundle.Unload(false);
         yield return 1;
    }

    private IEnumerator loadBundleAll(string path)
    {
        WWW bundle = new WWW(path);
        yield return bundle;
        Instantiate(bundle.assetBundle.Load("MyCubePreb"));
        Instantiate(bundle.assetBundle.Load("MySpherePreb"));
        yield return 1;
    }
}