C:/Program Files (x86)/Unity/Editor/Data/UnityExtensions/Unity/GUISystem/4.6.3/Editor/UnityEditor.UI.dll' is in timestamps but is not known in guidmapper...

以上这个是错误信息。

解决方案：

using UnityEngine;
using System.Collections.Generic;
using UnityEditor;
using System.Text.RegularExpressions;
using System.IO;
using System.Text;
public class ReimportUnityEngineUI
{
    [MenuItem("Assets/Reimport UI Assemblies", false, 100)]
    public static void ReimportUI()
    {
#if UNITY_4_6
        var path = EditorApplication.applicationContentsPath + "/UnityExtensions/Unity/GUISystem/{0}/{1}";
       var version = Regex.Match(Application.unityVersion, @"^[0-9]+\.[0-9]+\.[0-9]+").Value;
#else
        var path = EditorApplication.applicationContentsPath + "/UnityExtensions/Unity/GUISystem/{1}";
        var version = string.Empty;
#endif
        string engineDll = string.Format(path, version, "UnityEngine.UI.dll");
        string editorDll = string.Format(path, version, "Editor/UnityEditor.UI.dll");
        ReimportDll(engineDll);
        ReimportDll(editorDll);
    }
    static void ReimportDll(string path)
    {
        if (File.Exists(path))
            AssetDatabase.ImportAsset(path, ImportAssetOptions.ForceUpdate | ImportAssetOptions.DontDownloadFromCacheServer);
        else
            Debug.LogError(string.Format("DLL not found {0}", path));
    }
}