c# - 为什么代码永远不会到达覆盖 OnDrawNode 方法?
问题描述
在 form1 设计器中,我添加了一个树视图控件,并向其添加了一个根节点和一个子节点。并创建了绘画事件。
在 form1 代码中:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Test
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
AdvancedTreeView atv = new AdvancedTreeView();
}
private void Form1_Paint(object sender, PaintEventArgs e)
{
AdvancedTreeView.FillPolygonPoint(e);
}
}
}
AdvancedTreeView 类:
using System;
using System.Drawing;
using System.Windows.Forms;
public class AdvancedTreeView : TreeView
{
private static Image myimage;
public AdvancedTreeView()
{
DrawMode = TreeViewDrawMode.OwnerDrawAll;
ShowLines = false;
AlternateBackColor = BackColor;
}
public Color AlternateBackColor { get; set; }
protected override void OnDrawNode(DrawTreeNodeEventArgs e)
{
e.DrawDefault = true;
base.OnDrawNode(e);
// background
Color backColor = (GetTopNodeIndex(e.Node) & 1) == 0 ? BackColor : AlternateBackColor;
using (Brush b = new SolidBrush(backColor))
{
e.Graphics.FillRectangle(b, new Rectangle(0, e.Bounds.Top, ClientSize.Width, e.Bounds.Height));
}
// icon
if (e.Node.Nodes.Count > 0)
{
Image icon = GetIcon(e.Node.IsExpanded); // TODO: true=down;false:right
e.Graphics.DrawImage(icon, e.Bounds.Left - icon.Width - 3, e.Bounds.Top);
}
// text (due to OwnerDrawText mode, indenting of e.Bounds will be correct)
TextRenderer.DrawText(e.Graphics, e.Node.Text, Font, e.Bounds, ForeColor);
// indicate selection (if not by backColor):
if ((e.State & TreeNodeStates.Selected) != 0)
ControlPaint.DrawFocusRectangle(e.Graphics, e.Bounds);
}
private Image GetIcon(bool isExpanded)
{
return myimage;
}
private int GetTopNodeIndex(TreeNode node)
{
while (node.Parent != null)
node = node.Parent;
return Nodes.IndexOf(node);
}
public static void FillPolygonPoint(PaintEventArgs e)
{
// Create solid brush.
SolidBrush blueBrush = new SolidBrush(Color.Blue);
// Create points that define polygon.
Point point1 = new Point(0, 0);
Point point2 = new Point(20, 10);
Point point3 = new Point(0, 20);
Point[] curvePoints = { point1 , point2, point3 };
// Draw polygon to screen.
e.Graphics.FillPolygon(blueBrush, curvePoints);
myimage = new Bitmap(10,10,e.Graphics);
}
}
它到达了 AdvancedTreeView 的行:
DrawMode = TreeViewDrawMode.OwnerDrawAll;
但它永远不会进入 OnDrawNode。我也试过 TreeViewDrawMode.OwnerDrawText 但它永远不会到达 OnDrawNode。
解决方案
AdvancedTreeView
因此,这是旧答案中“原始”示例的更完整版本。
新成员是openedIcon
和closedIcon
字段、ArrowColor
属性和GetIcon
/InitIcon
方法。
public class AdvancedTreeView : TreeView
{
private Bitmap openedIcon, closedIcon;
public AdvancedTreeView()
{
DrawMode = TreeViewDrawMode.OwnerDrawText;
ShowLines = false;
AlternateBackColor = BackColor;
ArrowColor = SystemColors.WindowText;
}
public Color AlternateBackColor { get; set; }
public Color ArrowColor { get; set; }
protected override void OnDrawNode(DrawTreeNodeEventArgs e)
{
// background
Color backColor = (GetTopNodeIndex(e.Node) & 1) == 0 ? BackColor : AlternateBackColor;
using (Brush b = new SolidBrush(backColor))
{
e.Graphics.FillRectangle(b, new Rectangle(0, e.Bounds.Top, ClientSize.Width, e.Bounds.Height));
}
// icon
if (e.Node.Nodes.Count > 0)
{
Image icon = GetIcon(e.Node.IsExpanded);
e.Graphics.DrawImage(icon, e.Bounds.Left - icon.Width - 3, e.Bounds.Top);
}
// text (due to OwnerDrawText mode, indenting of e.Bounds will be correct)
TextRenderer.DrawText(e.Graphics, e.Node.Text, Font, e.Bounds, ForeColor);
// indicate selection (if not by backColor):
if ((e.State & TreeNodeStates.Selected) != 0)
ControlPaint.DrawFocusRectangle(e.Graphics, e.Bounds);
}
private int GetTopNodeIndex(TreeNode node)
{
while (node.Parent != null)
node = node.Parent;
return Nodes.IndexOf(node);
}
private Image GetIcon(bool nodeIsExpanded)
{
if (openedIcon == null)
InitIcons();
return nodeIsExpanded ? openedIcon : closedIcon;
}
private void InitIcons()
{
openedIcon = new Bitmap(16, 16);
closedIcon = new Bitmap(16, 16);
using (Brush b = new SolidBrush(ArrowColor))
{
using (Graphics g = Graphics.FromImage(openedIcon))
g.FillPolygon(b, new[] { new Point(0, 0), new Point(15, 0), new Point(8, 15), });
using (Graphics g = Graphics.FromImage(closedIcon))
g.FillPolygon(b, new[] { new Point(0, 0), new Point(15, 8), new Point(0, 15), });
}
}
}
设置颜色并添加节点后的设计器:
在运行时:
它仍然可以通过在更改颜色时使颜色无效等来改进......
推荐阅读
- reactjs - React、console.log 和 render 显示不同的值
- database - Gorm 更改列长
- php - Mysql - php_network_getaddresses:getaddrinfo 失败:名称或服务未知
- python - PyTorch:PyTorch 中的 numpy.linalg.multi_dot() 等价物是什么
- python - Odoo 14:在树视图中添加部分功能
- android - 在颤振中在android中实现人脸ID
- javascript - 事件侦听器仅附加到循环中的最后一个条目
- javascript - React-router-dom:History.push 连接路径并且不会重新路由应用程序
- java - 无法在 Android Studio 中访问 XML 表单主活动
- javascript - 使用 xlsx 数据创建网络。html 的