尽管我在谷歌上做了很多努力，但我还是找不到使用默认 .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。
我需要的是一种拥有两种不同高度的节点的方法。
理想情况下，我还希望一种节点类型也可以随着鼠标悬停而变大。
周围有聪明人吗？ :)
【问题讨论】：
我意识到这已经很老了……但我昨天发现了一些有趣的东西。 This thread 包含 Chris Forbes 的答案，这表明如果树视图具有 TVS_NONEVENHEIGHT 样式，则确实可以拥有可变高度的项目。我尝试了这个想法和他链接的github code snippet，发现这确实有效，但不能提供 100% 的灵活性（请参阅下面的限制列表）。我也不确定是否适合在鼠标悬停时更改项目的高度。
为什么它会做它所做的事情超出了我的理解，因为窗口样式似乎只是让用户能够设置一个奇数的项目高度而不是一个偶数。
限制和警告：
这里有一个 247 行的代码 sn-p 来演示这一点，只需用此代码替换 Windows 窗体应用程序的 Program.cs。
它仍然需要做很多工作，因为 OwnerDraw 代码还没有对绘制图标、树线、复选框等做任何事情，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);
}
}
}
}
【讨论】：
我没有找到您问题的答案。 @Frank 是正确的，这在 WinForms 中是不可能的。
但是，Microsoft 设计指南为 TreeViews 提供了一些替代方案如果您的层次结构只有两层深。
来自https://docs.microsoft.com/en-us/windows/win32/uxguide/ctrl-tree-views：
如果您需要显示超过两个级别的层次结构（不包括根节点），则必须使用树视图。
【讨论】：
这对于 System.Windows.Forms.TreeView 或我所知道的任何第 3 方替换都是不可能的。标准树视图的功能与 Windows 资源管理器文件夹视图中显示的功能相同。
也许您想向我们提供有关您的任务或目标的更多信息。这将使我们能够为您指出其他一些替代方案。
当然，您始终可以实现自己的树形视图，但我认为，根据您的要求，这可能会成为一项相当耗时的任务。
【讨论】：
如果您使用图标，最简单的方法是设置图标大小......这至少在紧凑框架中工作，我将图像高度设置为我想要对象的高度。如果你不想要一个图标，你可能只需要一个与你的背景相匹配的图标。
【讨论】：