void OnGUI() {
		const int height = 20;
		
		xFile = EditorGUI.ObjectField(
			new Rect(0, 0, position.width-16, height), "XFile" ,xFile, typeof(Object));
		
		if (xFile != null) {
			if (GUI.Button(new Rect(0, height+2, position.width/2, height), "Convert")) {
				XFileImporter imp = new XFileImporter(xFile);
				xFile = null;		// 読み終わったので空にする 
			}
		} else {
			EditorGUI.LabelField(new Rect(0, height+2, position.width, height), "Missing", "Select XFile");
		}
	}
    void OnGUI()
    {
        const int height = 20;

        xFile = EditorGUI.ObjectField(
            new Rect(0, 0, position.width - 16, height), "XFile", xFile, typeof(Object), true);

        if (xFile != null)
        {
            if (GUI.Button(new Rect(0, height + 2, position.width / 2, height), "Convert"))
            {
                XFileImporter.Import(xFile);
                xFile = null;                           // 読み終わったので空にする
            }
        }
        else
        {
            EditorGUI.LabelField(new Rect(0, height + 2, position.width, height), "Missing", "Select XFile");
        }
    }