TreeView：更改加减号图标[关闭]

Question

如何使用 C#.Net 将 TreeView Control 的 Plus Minus 图标更改为其他图标。

Answer 1

当你想自定义你的TreeView控件时，微软在TreeView控件上提供了一个名为TreeViewDrawMode的属性，它的值是一个枚举，它有3个值：Normal、OwnerDrawText、OwnerDrawAll，根据你的情况，您必须使用OwnerDrawAll。

将该属性设置为TreeViewDrawMode.OwnerDrawAll 后，当TreeView 的节点显示时，将触发一个名为DrawNode 的事件，因此您可以在那里处理您的绘图。自己画的时候，通常需要画3个东西：展开/折叠图标、节点图标、节点文本。

我的示例如下：

//define the icon file path
string minusPath = Application.StartupPath + Path.DirectorySeparatorChar + "minus.png";
string plusPath = Application.StartupPath + Path.DirectorySeparatorChar + "plus.png";
string nodePath = Application.StartupPath + Path.DirectorySeparatorChar + "directory.png";

public FrmTreeView()
{
    InitializeComponent();
    //setting to customer draw
    this.treeView1.DrawMode = TreeViewDrawMode.OwnerDrawAll;
    this.treeView1.DrawNode += new DrawTreeNodeEventHandler(treeView1_DrawNode);
}

void treeView1_DrawNode(object sender, DrawTreeNodeEventArgs e)
{
    Rectangle nodeRect = e.Node.Bounds;

    /*--------- 1. draw expand/collapse icon ---------*/
    Point ptExpand = new Point(nodeRect.Location.X - 20, nodeRect.Location.Y + 2);
    Image expandImg = null;
    if (e.Node.IsExpanded || e.Node.Nodes.Count < 1)
        expandImg = Image.FromFile(minusPath);
    else
        expandImg = Image.FromFile(plusPath);
    Graphics g = Graphics.FromImage(expandImg);
    IntPtr imgPtr = g.GetHdc();
    g.ReleaseHdc();
    e.Graphics.DrawImage(expandImg, ptExpand);

    /*--------- 2. draw node icon ---------*/
    Point ptNodeIcon = new Point(nodeRect.Location.X - 4, nodeRect.Location.Y + 2);
    Image nodeImg = Image.FromFile(nodePath);
    g = Graphics.FromImage(nodeImg);
    imgPtr = g.GetHdc();
    g.ReleaseHdc();
    e.Graphics.DrawImage(nodeImg, ptNodeIcon);

    /*--------- 3. draw node text ---------*/
    Font nodeFont = e.Node.NodeFont;
    if (nodeFont == null)
        nodeFont = ((TreeView)sender).Font;
    Brush textBrush = SystemBrushes.WindowText;
    //to highlight the text when selected
    if ((e.State & TreeNodeStates.Focused) != 0)
        textBrush = SystemBrushes.HotTrack;
    //Inflate to not be cut
    Rectangle textRect = nodeRect;
    //need to extend node rect
    textRect.Width += 40;
    e.Graphics.DrawString(e.Node.Text, nodeFont, textBrush, 
        Rectangle.Inflate(textRect, -12, 0));
}