前言
以前看别人的控件好看只有羡慕的份；以前觉得控件重绘是个很复杂的东西；以前知道MSDN很全面很专业却一直没有好好用起来；
作为初级程序猿，不能原地踏步，来吧，让我们一起把 TreeView 美化一下，每天进步一点点！
要点
1、WinForm自定义控件
2、重绘
3、MSDN使用
基础准备：利用MSDN查找我们需要的资料
1、进入MSDN技术资料库：http://msdn.microsoft.com/library
2、在右上角搜索栏里输入 TreeView
3、找到TreeView类（System.Windows.Forms）这一条【应该是搜索结果里的第二条】，里面详尽的介绍了这个类
这里直接附上地址：http://msdn.microsoft.com/zh-cn/library/system.windows.forms.treeview(v=vs.110).aspx
4、TreeView的方法、属性、事件等可以大概浏览下，知道有这个东西就行，继续往下看，我发现了我们需要的东西：
这里的意思是我们可以完全自定义TreeView的外观有2个要点：
一个是将DrawMode属性设置为TreeViewDrawMode.Normal以外的值；
一个是在DrawNode事件里我们可以进行对控件的皮肤修改
5、那DrawNode事件怎么用呢？截图中我们看到末尾的 DrawNode 字样是个超级链接，果断点进去一看究竟，于是发现了如下描述：
6、这段文字很详尽的介绍了DrawNode事件，我们可以总结出3个要点：
a、TreeView提供2种自定义模式，分别是OwnerDrawText和OwnerDrawAll。
OwnerDrawText：允许我们自定义节点的字体样式
OwnerDrawAll：允许我们自定义节点的所有元素样式，包括字体、背景、图标等
b、TreeNode有2个区域的概念：分别是【点击测试区域】和【整行区域】（整行区域这个名字自己取的，大家只要知道什么意思就行），来张图更容易理解
可能区域的范围图中不是很精确，但是我们能够大概的知道 【整行区域】 是这个节点这一行所有的面积，而 【点击测试区域】 是这个节点所有表现元素（图标+字体）所占的面积，从名字上我们也大概可以猜到这个【点击测试区域】跟用户鼠标点击的位置和对应的表现行为（单击选中，双击展开等）有关。
c、在DrawNode事件中，参数 DrawTreeNodeEventArgs.Bounds 我们可以获取到节点的【整行区域】，而 DrawTreeNodeEventArgs.Node.Bounds 我们可以获取到节点的【点击测试区域】
7、我们MSDN网页继续向下看，发现还有一段代码示例如下：
ps:示例什么的最好了，又直接又快捷，你懂的。而且MSDN里面的代码考虑都能周全，copy下来直接放到新建的程序里稍作调整就可以直接运行看到效果，然后我们可以逐行慢慢分析理解
using System; using System.Drawing; using System.Windows.Forms; public class TreeViewOwnerDraw : Form { private TreeView myTreeView; // Create a Font object for the node tags. Font tagFont = new Font("Helvetica", 8, FontStyle.Bold); public TreeViewOwnerDraw() { // Create and initialize the TreeView control. myTreeView = new TreeView(); myTreeView.Dock = DockStyle.Fill; myTreeView.BackColor = Color.Tan; myTreeView.CheckBoxes = true; // Add nodes to the TreeView control. TreeNode node; for (int x = 1; x < 4; ++x) { // Add a root node to the TreeView control. node = myTreeView.Nodes.Add(String.Format("Task {0}", x)); for (int y = 1; y < 4; ++y) { // Add a child node to the root node. node.Nodes.Add(String.Format("Subtask {0}", y)); } } myTreeView.ExpandAll(); // Add tags containing alert messages to a few nodes // and set the node background color to highlight them. myTreeView.Nodes[1].Nodes[0].Tag = "urgent!"; myTreeView.Nodes[1].Nodes[0].BackColor = Color.Yellow; myTreeView.SelectedNode = myTreeView.Nodes[1].Nodes[0]; myTreeView.Nodes[2].Nodes[1].Tag = "urgent!"; myTreeView.Nodes[2].Nodes[1].BackColor = Color.Yellow; // Configure the TreeView control for owner-draw and add // a handler for the DrawNode event. myTreeView.DrawMode = TreeViewDrawMode.OwnerDrawText; myTreeView.DrawNode += new DrawTreeNodeEventHandler(myTreeView_DrawNode); // Add a handler for the MouseDown event so that a node can be // selected by clicking the tag text as well as the node text. myTreeView.MouseDown += new MouseEventHandler(myTreeView_MouseDown); // Initialize the form and add the TreeView control to it. this.ClientSize = new Size(292, 273); this.Controls.Add(myTreeView); } // Clean up any resources being used. protected override void Dispose(bool disposing) { if (disposing) { tagFont.Dispose(); } base.Dispose(disposing); } [STAThreadAttribute()] static void Main() { Application.Run(new TreeViewOwnerDraw()); } // Draws a node. private void myTreeView_DrawNode( object sender, DrawTreeNodeEventArgs e) { // Draw the background and node text for a selected node. if ((e.State & TreeNodeStates.Selected) != 0) { // Draw the background of the selected node. The NodeBounds // method makes the highlight rectangle large enough to // include the text of a node tag, if one is present. e.Graphics.FillRectangle(Brushes.Green, NodeBounds(e.Node)); // Retrieve the node font. If the node font has not been set, // use the TreeView font. Font nodeFont = e.Node.NodeFont; if (nodeFont == null) nodeFont = ((TreeView)sender).Font; // Draw the node text. e.Graphics.DrawString(e.Node.Text, nodeFont, Brushes.White, Rectangle.Inflate(e.Bounds, 2, 0)); } // Use the default background and node text. else { e.DrawDefault = true; } // If a node tag is present, draw its string representation // to the right of the label text. if (e.Node.Tag != null) { e.Graphics.DrawString(e.Node.Tag.ToString(), tagFont, Brushes.Yellow, e.Bounds.Right + 2, e.Bounds.Top); } // If the node has focus, draw the focus rectangle large, making // it large enough to include the text of the node tag, if present. if ((e.State & TreeNodeStates.Focused) != 0) { using (Pen focusPen = new Pen(Color.Black)) { focusPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot; Rectangle focusBounds = NodeBounds(e.Node); focusBounds.Size = new Size(focusBounds.Width - 1, focusBounds.Height - 1); e.Graphics.DrawRectangle(focusPen, focusBounds); } } } // Selects a node that is clicked on its label or tag text. private void myTreeView_MouseDown(object sender, MouseEventArgs e) { TreeNode clickedNode = myTreeView.GetNodeAt(e.X, e.Y); if (NodeBounds(clickedNode).Contains(e.X, e.Y)) { myTreeView.SelectedNode = clickedNode; } } // Returns the bounds of the specified node, including the region // occupied by the node label and any node tag displayed. private Rectangle NodeBounds(TreeNode node) { // Set the return value to the normal node bounds. Rectangle bounds = node.Bounds; if (node.Tag != null) { // Retrieve a Graphics object from the TreeView handle // and use it to calculate the display width of the tag. Graphics g = myTreeView.CreateGraphics(); int tagWidth = (int)g.MeasureString (node.Tag.ToString(), tagFont).Width + 6; // Adjust the node bounds using the calculated value. bounds.Offset(tagWidth/2, 0); bounds = Rectangle.Inflate(bounds, tagWidth/2, 0); g.Dispose(); } return bounds; } }
8、这段代码里我发现了几个实用的：
1、TreeView 的 GetNodeAt 方法支持根据鼠标点击坐标获取对应节点：
TreeNode clickedNode = myTreeView.GetNodeAt(e.X, e.Y);
2、TreeView 的 CreateGraphics 方法可以创建当前实例的 Graphics 对象：
Graphics g = myTreeView.CreateGraphics();
g.Dispose();
3、DrawNode事件中的节点状态判断写法：
例如判断当前节点为选中状态 if ((e.State & TreeNodeStates.Selected) != 0)
4、描绘文字的方法：
e.Graphics.DrawString(e.Node.Text, nodeFont, Brushes.White,Rectangle.Inflate(e.Bounds, 2, 0));
5、描绘背景的方法：
e.Graphics.DrawRectangle(focusPen, focusBounds);
9、好的，准备工作差不多了，开始我们的皮肤美化之旅吧！
项目创建
步骤一：新建Winfrom项目，并新建一个自定义控件
步骤二：修改MyTreeView类继承TreeView，注意这里需要添加引用 using System.Windows.Forms;
步骤三：根据自己需要修改样式，下面是我的代码：
public partial class BaseTreeView : TreeView { Color drawTextColor = Color.FromArgb(81, 81, 81); public BaseTreeView() { InitializeComponent(); this.DrawMode = TreeViewDrawMode.OwnerDrawAll; this.FullRowSelect = true; this.ItemHeight = 23; this.HotTracking = true; this.ShowLines = true; } protected override void OnDrawNode(DrawTreeNodeEventArgs e) { base.OnDrawNode(e); //节点背景绘制 if (e.Node.IsSelected) { e.Graphics.DrawImage(Resources.tree_Selected, e.Bounds); } else if ((e.State & TreeNodeStates.Hot) != 0)//|| currentMouseMoveNode == e.Node) { e.Graphics.DrawImage(Resources.tree_Hover, e.Bounds); } else { e.Graphics.FillRectangle(Brushes.White, e.Bounds); } //节点头图标绘制 if (e.Node.IsExpanded) { e.Graphics.DrawImage(Resources.tree_NodeExpend, e.Node.Bounds.X - 12, e.Node.Bounds.Y + 6); } else if (e.Node.IsExpanded == false && e.Node.Nodes.Count > 0) { e.Graphics.DrawImage(Resources.tree_NodeCollaps, e.Node.Bounds.X - 12, e.Node.Bounds.Y + 6); } //文本绘制 using (Font foreFont = new Font(this.Font, FontStyle.Regular)) using (Brush drawTextBrush = new SolidBrush(drawTextColor)) { e.Graphics.DrawString(e.Node.Text, foreFont, drawTextBrush, e.Node.Bounds.Left + 5, e.Node.Bounds.Top + 5); } } protected override void OnMouseDoubleClick(MouseEventArgs e) { base.OnMouseDoubleClick(e); TreeNode tn = this.GetNodeAt(e.Location); //调整【点击测试区域】大小，包括图标 Rectangle bounds = new Rectangle(tn.Bounds.Left - 12, tn.Bounds.Y, tn.Bounds.Width - 5, tn.Bounds.Height); if (tn != null && bounds.Contains(e.Location) == false) { if (tn.IsExpanded == false) tn.Expand(); else tn.Collapse(); } } protected override void OnMouseClick(MouseEventArgs e) { base.OnMouseClick(e); TreeNode tn = this.GetNodeAt(e.Location); this.SelectedNode = tn; } TreeNode currentNode = null; protected override void OnMouseMove(MouseEventArgs e) { base.OnMouseMove(e); TreeNode tn = this.GetNodeAt(e.Location); Graphics g = this.CreateGraphics(); if (currentNode != tn) { //绘制当前节点的hover背景 if (tn != null) OnDrawNode(new DrawTreeNodeEventArgs(g, tn, new Rectangle(0, tn.Bounds.Y, this.Width, tn.Bounds.Height), TreeNodeStates.Hot)); //取消之前hover的节点背景 if (currentNode != null) OnDrawNode(new DrawTreeNodeEventArgs(g, currentNode, new Rectangle(0, currentNode.Bounds.Y, this.Width, currentNode.Bounds.Height), TreeNodeStates.Default)); } currentNode = tn; g.Dispose(); } protected override void OnMouseLeave(EventArgs e) { base.OnMouseLeave(e); //移出控件时取消Hover背景 if (currentNode != null) { Graphics g = this.CreateGraphics(); OnDrawNode(new DrawTreeNodeEventArgs(g, currentNode, new Rectangle(0, currentNode.Bounds.Y, this.Width, currentNode.Bounds.Height), TreeNodeStates.Default)); } } }
效果如下图：深蓝色为节点选中时的效果，淡蓝色为鼠标停留在节点上的效果
说明1：因为默认的TreeView点击非【点击测试区域】时是不触发动作效果的【单击节点选中效果、双击节点展开等效果】
原本想尝试修改节点的【点击测试区域】扩大到【整行区域】，后来没有找到方法，所以只能变通的实现这个效果，因此在我的代码里在其它事件里也进行了处理，不过还好我要的效果是实现了
说明2：demo下载