unity3d Resources.Load动态加载资源

　　初步整理并且学习unity3d资源加载方法，预计用时两天完成入门学习Unity3d常用两种加载资源方案：Resources.Load和AssetBundle

Resources.Load就是从一个缺省打进程序包里的AssetBundle里加载资源而一般AssetBundle文件需要你自己创建，运行时动态加载，

可以指定路径和来源的。其实场景里所有静态的对象也有这么一个加载过程，只是Unity后台替你自动完成

一：Resources.Load：使用这种方式加载资源，首先需要下Asset目录下创建一个名为Resources的文件夹，这个命名是U3D规定的方式，然后把资源文件放进去，

当然也可以在Resources中再创建子文件夹，当然在代码加载时需要添加相应的资源路径，下面是一个简demo，两个预设，Cube和Sphere，

其中Cube放在Resource中的Prebs中，而Sphere放在Resources跟目录下，下面分别实现Resources.Load资源的加载

using UnityEngine;
using System.Collections;

public class LoadResDemo : MonoBehaviour {

    private string cubePath = "Prebs/MyCubePreb";
    private string spherePath = "MySpherePreb";
    void Start () {
        //把资源加载到内存中
        Object  cubePreb = Resources.Load(cubePath, typeof(GameObject));
        //用加载得到的资源对象，实例化游戏对象，实现游戏物体的动态加载
        GameObject cube = Instantiate(cubePreb) as GameObject;

        //以下同理实现Sphere的动态实例化
        //把资源加载到内存中
        Object spherePreb = Resources.Load(spherePath, typeof(GameObject));
        //用加载得到的资源对象，实例化游戏对象，实现游戏物体的动态加载
        GameObject sphere = Instantiate(spherePreb) as GameObject;
    }

    void Update () {

    }
}

　　将上面的脚本附加到某个游戏对象上，在运行游戏时就可以看到场景中动态创建的上面的游戏对象了

上面是第一种使用Resources.Load()的方式动态加载游戏对象的，然而在项目中更长用的却是第二种使用AssetBundle的方式动态加载游戏对象。

使用AssetBundle打包预设或者场景可以将与其相关的所有资源打包，这样很好地解决资源的依赖问题，使得我们可以方便的加载GameObject

首先需要打包资源：

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

    [MenuItem("Custom Bundle/Create Bundel Main")]
    public static void creatBundleMain()
    {
        //获取选择的对象的路径
        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 == )
        {
            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();
    }

}

把上面的代码放在Editor中，在菜单栏中就可以看见自定的菜单项，选中需要打包的预设，就可以把对应的预设打包并输出到StreamAssets中了

然后是动态加载资源：

using UnityEngine;
using System.Collections;

public class LoadBundleTest : MonoBehaviour {
    //不同平台下StreamingAssets的路径是不同的，这里需要注意一下。
    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 ;
    }

    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 ;
    }
}