public void Initialize()
        {
            if (treeViewState == null)
            {
                treeViewState = new TreeViewState();
            }
            treeView        = new CustomAssetImporterEditorWindowTreeView(treeViewState);
            horizontalState = new SplitterState(new float[] { position.width * 0.15f, position.width * 0.85f },
                                                new int[] { 100, 250 }, new int[] { 200, 1000 });

            if (audioImporterSettings == null)
            {
                audioImporterSettings = FileHelper.GetAudioImporter();
            }
            if (textureImporterSettings == null)
            {
                textureImporterSettings = FileHelper.GetTextureImporter();
            }
            if (modelImporterSettings == null)
            {
                modelImporterSettings = FileHelper.GetModelImporter();
            }

            if (audioImporterEditorItem == null || audioImporterEditorItem.Data == null)
            {
                audioImporterEditorItem = new CustomAudioImporterSettingsEditorItem(audioImporterSettings);
            }
            if (textureImporterEditorItem == null || textureImporterEditorItem.Data == null)
            {
                textureImporterEditorItem = new CustomTextureImporterSettingsEditorItem(textureImporterSettings);
            }
            if (modelImporterEditorItem == null || modelImporterEditorItem.Data == null)
            {
                modelImporterEditorItem = new CustomModelImporterSettingsEditorItem(modelImporterSettings);
            }
            audioImporterEditorItem.Initialize();
            textureImporterEditorItem.Initialize();
            modelImporterEditorItem.Initialize();

            Repaint();

            IsInitialized = true;
            IsFirstGUI    = true;
        }