绘制程序概述

TreeList 的绘制程序是实现了 ITreeListPaintHelper 接口 (下面的小节描述了此接口) 的对象。要创建自定义绘制程序，则需要创建一个实现了 ITreeListPaintHelper 接口的类。或者可以从 TreeList 的默认绘制程序 —— DevExpress.XtraTreeList.Painter.TreeListPaintHelper 类派生，从而创建自定义绘制程序类。

要使用自定义绘制程序类，则把它的一个实例指派到 TreeList.Painter 对象的 DefaultPainter 属性。此属性引用绘制程序类的实例，此实例被用于绘制 TreeList 的元素。最初，此属性引用一个 TreeListPaintHelper 对象。

树状列表绘制帮助器必须支持 ITreeListPaintHelper 接口。此接口声明了绘制特定类型元素的方法。下面的代码是此接口的声明。

public interface ITreeListPaintHelper {
   void DrawOpenCloseButton(CustomDrawNodeButtonEventArgs e);
   void DrawColumn(CustomDrawColumnHeaderEventArgs e);
   void DrawNodePreview(CustomDrawNodePreviewEventArgs e);
   void DrawNodeSelectImage(CustomDrawNodeImagesEventArgs e);
   void DrawNodeStateImage(CustomDrawNodeImagesEventArgs e);
   void DrawIndicator(CustomDrawNodeIndicatorEventArgs e);
   void DrawFooterBackGround(CustomDrawEventArgs e);
   void DrawRowFooterCell(CustomDrawRowFooterCellEventArgs e);
   void DrawFooterCell(CustomDrawFooterCellEventArgs e);
   void DrawNodeCell(CustomDrawNodeCellEventArgs e);
}

下表列出了此接口的方法，提供了每个方法的简要说明，并且列出了可以用于代替它的自定义绘制事件。

方法	说明	自定义绘制事件
DrawOpenCloseButton	绘制分组按钮。获取一个 CustomDrawNodeButtonEventArgs 对象作为参数。	TreeList.CustomDrawNodeButton
DrawColumn	绘制列标头面板的元素。获取一个 CustomDrawColumnHeaderEventArgs 对象作为参数。	TreeList.CustomDrawColumnHeader
DrawNodePreview	绘制预览区。获取一个 CustomDrawNodePreviewEventArgs 对象作为参数。	TreeList.CustomDrawNodePreview
DrawNodeSelectImage	绘制选中图像。获取一个 CustomDrawNodeImagesEventArgs 对象作为参数。	TreeList.CustomDrawNodeImages
DrawNodeStateImage	绘制状态图像。获取一个 CustomDrawNodeImagesEventArgs 对象作为参数。	TreeList.CustomDrawNodeImages
DrawIndicator	绘制批示器单元格。获取一个 CustomDrawNodeIndicatorEventArgs 对象作为参数。	TreeList.CustomDrawNodeIndicator
DrawFooterBackGround	绘制汇总脚注的背景。获取一个 CustomDrawEventArgs 对象作为参数。	TreeList.CustomDrawFooter
DrawRowFooterCell	绘制行脚注单元格。获取一个 CustomDrawRowFooterCellEventArgs 对象作为参数。	TreeList.CustomDrawRowFooterCell
DrawFooterCell	绘制汇总脚注单元格。获取一个 CustomDrawFooterCellEventArgs 对象作为参数。	TreeList.CustomDrawFooterCell
DrawNodeCell	绘制节点单元格。获取一个 CustomDrawNodeCellEventArgs 对象作为参数。	TreeList.CustomDrawNodeCell

下面的代码创建了一个简单的绘制帮助器，它派生于标准的 TreeListPaintHelper 类。 DrawFooterBackGround 方法被重写，以便实现自定义绘制汇总脚注。

下面的插图展示了在运行代码之前和之后的 XtraTreeList 控件。

C#	复制代码
using DevExpress.Utils; using DevExpress.XtraTreeList; using DevExpress.XtraTreeList.Painter; using System.Drawing.Drawing2D; // ... public class SimplePaintHelper : TreeListPaintHelper { internal SimplePaintHelper(ImageList il_Indicator) : base(il_Indicator) {} public override void DrawFooterBackGround(CustomDrawEventArgs e) { LinearGradientBrush brush = new LinearGradientBrush(e.Bounds, Color.FromArgb(244, 210, 227), Color.FromArgb(207, 196, 230), LinearGradientMode.Vertical); e.Graphics.FillRectangle(brush, e.Bounds); } } //... // Use the painter: treeList1.Painter.DefaultPaintHelper = new SimplePaintHelper(treeList1.Painter.IndicatorImages);

C#

复制代码

using DevExpress.Utils;
using DevExpress.XtraTreeList;
using DevExpress.XtraTreeList.Painter;
using System.Drawing.Drawing2D;
// ...
public class SimplePaintHelper : TreeListPaintHelper {
   internal SimplePaintHelper(ImageList il_Indicator) : base(il_Indicator) {}
   public override void DrawFooterBackGround(CustomDrawEventArgs e) {
      LinearGradientBrush brush = new LinearGradientBrush(e.Bounds, 
Color.FromArgb(244, 210, 227), Color.FromArgb(207, 196, 230), 
LinearGradientMode.Vertical);
      e.Graphics.FillRectangle(brush, e.Bounds);
   }
}

//...
// Use the painter:
treeList1.Painter.DefaultPaintHelper = new SimplePaintHelper(treeList1.Painter.IndicatorImages);

Visual Basic	复制代码
Imports DevExpress.Utils Imports DevExpress.XtraTreeList Imports DevExpress.XtraTreeList.Painter Imports System.Drawing.Drawing2D ' ... Public Class SimplePaintHelper Inherits TreeListPaintHelper Friend Sub New(ByVal il_Indicator As ImageList) MyBase.New(il_Indicator) End Sub Public Overrides Sub DrawFooterBackGround(ByVal e As CustomDrawEventArgs) Dim Brush As New LinearGradientBrush(e.Bounds, Color.FromArgb(244, 210, 227), Color.FromArgb(207, 196, 230), LinearGradientMode.Vertical) e.Graphics.FillRectangle(Brush, e.Bounds) End Sub End Class '... ' Use the painter: TreeList1.Painter.DefaultPaintHelper = New SimplePaintHelper(TreeList1.Painter.IndicatorImages)

Visual Basic

复制代码

Imports DevExpress.Utils
Imports DevExpress.XtraTreeList
Imports DevExpress.XtraTreeList.Painter
Imports System.Drawing.Drawing2D
' ...
Public Class SimplePaintHelper
   Inherits TreeListPaintHelper

   Friend Sub New(ByVal il_Indicator As ImageList)
      MyBase.New(il_Indicator)
   End Sub

   Public Overrides Sub DrawFooterBackGround(ByVal e As CustomDrawEventArgs)
      Dim Brush As New LinearGradientBrush(e.Bounds, Color.FromArgb(244, 210, 227), 
Color.FromArgb(207, 196, 230), LinearGradientMode.Vertical)
      e.Graphics.FillRectangle(Brush, e.Bounds)
   End Sub
End Class

'...
' Use the painter:
TreeList1.Painter.DefaultPaintHelper = New SimplePaintHelper(TreeList1.Painter.IndicatorImages)

TreeList 的绘制程序

ITreeListPaintHelper 接口

示例