C# TreeView 中节点的可变高度

Question

尽管我在谷歌上进行了努力，但我找不到使用默认 .NET 树视图并为该树视图中的每个节点设置可变高度的解决方案。

我需要一种拥有两种不同高度的节点的方法。

理想情况下，我还希望当鼠标悬停在一种节点类型上时它也可以变得更大。

周围有聪明人吗？:)

Answer 1

我意识到这已经很老了......但我昨天发现了一些有趣的东西。该线程包含 Chris Forbes 的答案，该答案表明如果树视图具有TVS_NONEVENHEIGHT样式，则确实可以具有可变高度的项目。我尝试了这个想法和他链接到的github 代码片段，发现这确实有效，但并没有提供 100% 的灵活性（请参阅下面的限制列表）。我也不确定是否适合更改鼠标悬停时项目的高度。

但为什么它会这样做，这超出了我的理解，因为窗口样式似乎只是让用户能够设置奇数项目高度而不是偶数项目高度。

限制和注意事项：

• 它需要大量工作，因为节点必须完全由所有者绘制。在这方面，此代码示例的功能并不完整。
• 您只能将项目高度设置为控件的ItemHeight属性的倍数（事实上，您实际上将其设置为您想要的因子，1、2、3...）。我尝试将控件的 ItemHeight 属性设置为 1，然后将节点高度设置为我想要的像素高度。它似乎确实有效，但如果您在设计时添加项目，它只会在设计器中产生奇怪且破碎的结果。不过我没有对此进行彻底测试。
• 如果节点尚未添加到 TreeNodeCollection，则无法设置高度，因为尚未创建 TreeNode 的句柄。
• 您无法在设计时修改项目高度。
• 我不经常使用 pinvoke 的东西，所以其中一些定义可能需要一些工作。例如，TVITEMEX的原始定义有一些我不知道如何复制的条件条目。

下面的 247 行代码片段演示了这一点，只需用此代码替换 Windows 窗体应用程序的 Program.cs 即可。

它仍然需要大量的工作，因为 OwnerDraw 代码还没有做任何关于绘制图标、树线、复选框等的事情，但我认为这是一个非常令人惊讶的发现，值得在这里发布。

using System;
using System.ComponentModel;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace TreeTest
{
  static class Program
  {
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
      Application.EnableVisualStyles();
      Application.SetCompatibleTextRenderingDefault(false);
      Application.Run(new TreeForm());
    }
  }

  public static class NativeExtensions
  {
    public const int TVS_NONEVENHEIGHT = 0x4000;

    [DllImport("user32")]
    //private static extern IntPtr SendMessage(IntPtr hwnd, uint msg, IntPtr wp, IntPtr lp);
    private static extern IntPtr SendMessage(IntPtr hwnd, uint msg, IntPtr wp, ref TVITEMEX lp);

    private const int TVM_GETITEM = 0x1100 + 62;
    private const int TVM_SETITEM = 0x1100 + 63;

    [StructLayout(LayoutKind.Sequential)]
    private struct TVITEMEX
    {
      public uint mask;
      public IntPtr hItem;
      public uint state;
      public uint stateMask;
      public IntPtr pszText;
      public int cchTextMax;
      public int iImage;
      public int iSelectedImage;
      public int cChildren;
      public IntPtr lParam;
      public int iIntegral;
      public uint uStateEx;
      public IntPtr hwnd;
      public int iExpandedImage;
      public int iReserved;
    }

    [Flags]
    private enum Mask : uint
    {
      Text = 1,
      Image = 2,
      Param = 4,
      State = 8,
      Handle = 16,
      SelectedImage = 32,
      Children = 64,
      Integral = 128,
    }

    /// <summary>
    /// Get a node's height. Will throw an error if the Node has not yet been added to a TreeView,
    /// as it's handle will not exist.
    /// </summary>
    /// <param name="tn">TreeNode to work with</param>
    /// <returns>Height in multiples of ItemHeight</returns>
    public static int GetHeight(this TreeNode tn)
    {
      TVITEMEX tvix = new TVITEMEX
      {
        mask = (uint)(Mask.Handle | Mask.Integral),
        hItem = tn.Handle,
        iIntegral = 0
      };
      SendMessage(tn.TreeView.Handle, TVM_GETITEM, IntPtr.Zero, ref tvix);
      return tvix.iIntegral;
    }

    /// <summary>
    /// Set a node's height. Will throw an error if the Node has not yet been added to a TreeView,
    /// as it's handle will not exist.
    /// </summary>
    /// <param name="tn">TreeNode to work with</param>
    /// <param name="height">Height in multiples of ItemHeight</param>
    public static void SetHeight(this TreeNode tn, int height)
    {
      TVITEMEX tvix = new TVITEMEX
      {
        mask = (uint)(Mask.Handle | Mask.Integral),
        hItem = tn.Handle,
        iIntegral = height
      };
      SendMessage(tn.TreeView.Handle, TVM_SETITEM, IntPtr.Zero, ref tvix);
    }
  }

  public class TreeViewTest : TreeView
  {
    public TreeViewTest()
    {
      // Do DoubleBuffered painting
      SetStyle(ControlStyles.AllPaintingInWmPaint, true);
      SetStyle(ControlStyles.OptimizedDoubleBuffer, true);

      // Set value for owner drawing ...
      DrawMode = TreeViewDrawMode.OwnerDrawAll;
    }

    /// <summary>
    /// For TreeNodes to support variable heights, we need to apply the
    /// TVS_NONEVENHEIGHT style to the control.
    /// </summary>
    protected override CreateParams CreateParams
    {
      get
      {
        var cp = base.CreateParams;
        cp.Style |= NativeExtensions.TVS_NONEVENHEIGHT;
        return cp;
      }
    }

    /// <summary>
    /// Do not tempt anyone to change the DrawMode property, be it via code or via
    /// Property grid. It's still possible via code though ...
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
      EditorBrowsable(EditorBrowsableState.Never)]
    public new TreeViewDrawMode DrawMode
    {
      get { return base.DrawMode; }
      set { base.DrawMode = value; }
    }

    /// <summary>
    /// OwnerDraw code. Still needs a lot of work, no tree lines, symbols, checkboxes etc. are drawn
    /// yet, just the plain item text and background ...
    /// </summary>
    /// <param name="e"></param>
    protected override void OnDrawNode(DrawTreeNodeEventArgs e)
    {
      e.DrawDefault = false;

      // Draw window colour background
      e.Graphics.FillRectangle(SystemBrushes.Window, e.Bounds);

      // Draw selected item background
      if (e.Node.IsSelected)
        e.Graphics.FillRectangle(SystemBrushes.Highlight, e.Node.Bounds);

      // Draw item text
      TextRenderer.DrawText(e.Graphics, e.Node.Text, Font, e.Node.Bounds,
        e.Node.IsSelected ? SystemColors.HighlightText : SystemColors.WindowText,
        Color.Transparent, TextFormatFlags.Top | TextFormatFlags.NoClipping);

      // Draw focus rectangle
      if (Focused && e.Node.IsSelected)
        ControlPaint.DrawFocusRectangle(e.Graphics, e.Node.Bounds);

      base.OnDrawNode(e);
    }

    /// <summary>
    /// Without this piece of code, for some reason, drawing of items that get selected/unselected
    /// is deferred until MouseUp is received.
    /// </summary>
    /// <param name="e"></param>
    protected override void OnMouseDown(MouseEventArgs e)
    {
      base.OnMouseDown(e);
      TreeNode clickedNode = GetNodeAt(e.X, e.Y);
      if (clickedNode.Bounds.Contains(e.X, e.Y))
      {
        SelectedNode = clickedNode;
      }
    }
  }

  public class TreeForm : Form
  {
    public TreeForm() { InitializeComponent(); }

    private System.ComponentModel.IContainer components = null;

    protected override void Dispose(bool disposing)
    {
      if (disposing && (components != null))
      {
        components.Dispose();
      }
      base.Dispose(disposing);
    }

    private void InitializeComponent()
    {
      this.treeViewTest1 = new TreeTest.TreeViewTest();
      this.SuspendLayout();
      // 
      // treeViewTest1
      // 
      this.treeViewTest1.Dock = System.Windows.Forms.DockStyle.Fill;
      this.treeViewTest1.Location = new System.Drawing.Point(0, 0);
      this.treeViewTest1.Name = "treeViewTest1";
      this.treeViewTest1.Size = new System.Drawing.Size(284, 262);
      this.treeViewTest1.TabIndex = 0;
      // 
      // Form2
      // 
      this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
      this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
      this.ClientSize = new System.Drawing.Size(284, 262);
      this.Controls.Add(this.treeViewTest1);
      this.Name = "Form2";
      this.Text = "Form2";
      this.ResumeLayout(false);
    }

    private TreeViewTest treeViewTest1;

    protected override void OnLoad(EventArgs e)
    {
      base.OnLoad(e);

      AddNodes(treeViewTest1.Nodes, 0, new Random());
    }

    private void AddNodes(TreeNodeCollection nodes, int depth, Random r)
    {
      if (depth > 2) return;

      for (int i = 0; i < 3; i++)
      {
        int height = r.Next(1, 4);
        TreeNode tn = new TreeNode { Text = $"Node {i + 1} at depth {depth} with height {height}" };
        nodes.Add(tn);
        tn.SetHeight(height);
        AddNodes(tn.Nodes, depth + 1, r);
      }
    }
  }
}