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我定义SelecterControl了包含透明图像控件的用户控件（背景中Roll有透明图像）。

我想把前面的控制权移过来SelecterControl。

当这样做时，透明区域SelecterControl不清晰。

在此处输入图像描述

我的完整代码如下：

using System;
using System.Drawing;
using System.Windows.Forms;
using System.IO;

namespace TestControl
{
public partial class SelecterControl : UserControl
{
    private Roll roll;

    public SelecterControl()
    {
        InitializeComponent();
        BackgroundImage = Image.FromStream(new MemoryStream(Convert.FromBase64String("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")));
        SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        BackColor = Color.Transparent;
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle |= 0x20;
            return cp;
        }
    }

    protected override void OnPaintBackground(PaintEventArgs e)
    {
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        if (BackgroundImage != null)
            e.Graphics.DrawImage(BackgroundImage, e.ClipRectangle, e.ClipRectangle, GraphicsUnit.Pixel);
    }

    #region Roll Horizontal Movement

    int strtX;

    private void roll_MouseDown(object sender, MouseEventArgs e)
    {
        strtX = e.X;
    }

    private void roll_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Left)
            roll.Left += e.X - strtX;
    }

    #endregion

    #region Designer generated code

    private System.ComponentModel.IContainer components = null;

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

    private void InitializeComponent()
    {
        System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(SelecterControl));
        this.roll = new MapControl.Roll();
        this.SuspendLayout();
        // 
        // roll
        // 
        this.roll.BackColor = System.Drawing.Color.Transparent;
        //this.roll.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("roll.BackgroundImage")));
        this.roll.Location = new System.Drawing.Point(87, 1);
        this.roll.Name = "roll";
        this.roll.Size = new System.Drawing.Size(13, 18);
        this.roll.TabIndex = 0;
        this.roll.MouseDown += new System.Windows.Forms.MouseEventHandler(this.roll_MouseDown);
        this.roll.MouseMove += new System.Windows.Forms.MouseEventHandler(this.roll_MouseMove);
        // 
        // SelecterControl
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        //this.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("$this.BackgroundImage")));
        this.Controls.Add(this.roll);
        this.Name = "SelecterControl";
        this.Size = new System.Drawing.Size(251, 22);
        this.ResumeLayout(false);

    }

    #endregion
}


class Roll : Control
{
    public Roll()
    {
        BackgroundImage = Image.FromStream(new MemoryStream(Convert.FromBase64String("iVBORw0KGgoAAAANSUhEUgAAAA0AAAASCAYAAACAa1QyAAAABmJLR0QA/wD/AP+gvaeTAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3RJTUUH3AgFDR0RM4ISugAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAA5UlEQVQoz2NkQAWCUMyARMPAexjNAhORjTul5GEhd5cBC1jc4h/249nJ9zCNjAwMDAwaufeVbDU57zIwMLyfnCKKYkPunNcwjek/np28x8DAcI+JgYGBAVnDozd/4BoevfnDMDlFlIGBgYEhtmbjTJizmWAKYBrkROAuZpATYUHRCANM2PygU/iIQafwEQMuwMRABhjVRIkmFmyCV/rl8Ol5z4SUxt7DUgByMpITYYGnP1iChWkSYmBgEIRpRE5GMA3LJ2abQDW9Z4QpSJ32QpCBgeEdNvesnt+p/OF0/3ukPEU6AADyU1AuXNEg+gAAAABJRU5ErkJggg==")));
        SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        BackColor = Color.Transparent;
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle |= 0x20;
            return cp;
        }
    }

    protected override void OnPaintBackground(PaintEventArgs e)
    {
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        if (BackgroundImage != null)
            e.Graphics.DrawImage(BackgroundImage, e.ClipRectangle, e.ClipRectangle, GraphicsUnit.Pixel);
    }
}
}

这个问题的原因是什么？谢谢你的帮助。

4

1 回答 1

1 
    this.roll.Size = new System.Drawing.Size(13, 18);

这是您代码中的核心问题，“滚动”控件太小。当您在 CreateParams 属性中使用 WS_EX_TRANSPARENT 标志时，您要求 Windows 确保您的控件后面的窗口始终首先绘制。它为您的“滚动”控件设置背景像素，以便它可以在它们上面绘制自己的东西。

麻烦的是，您的滚动控件太小了，以至于在您移动它之后，它还不足以覆盖之前绘制的杂散像素。它们不再位于滚动控制窗口内。所以他们会留在那里，产生你看到的拖尾效果。

避免这种情况的唯一方法是使您的滚动控制更大，以便它始终捕获这些像素。实际上，与滑块的范围一样大。问题是，你现在失去了让“滚动”成为它自己的控制的所有好处。像点击测试这样的事情变得复杂，你需要知道拇指在哪里才能知道用户点击了它。

您不妨创建一个同时绘制滑块和拇指的控件。所需的代码完全相同。而且它会更有效，因为您使用更少的系统资源，窗口是昂贵的对象。

于 2012-08-05T17:02:39.137 回答