树视图：更改正负图标

Question

我如何改变正负TreeView控件的图标使用C＃.NET一些其他的图标。

Answer 1

当你想自定义你的treeview控件时，Microsoft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和OwnerDrawAll，在你的情况下，你必须使用OwnerDrawAll 。在将该属性设置为OwnerDrawAll后，当显示树视图的节点时，将触发名为“DrawNode”的事件，以便您可以在那里处理您的绘图。当你自己绘制它时，通常需要绘制3件东西：展开/折叠图标，节点图标，节点文本。 我的样品低于：

//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)); 
    }