我有这个事件：
protected override void OnMouseDown(MouseEventArgs e)
{
mOffset = new Point(Width / 2 - e.X, Height / 2 - e.Y);
mCurrentPoint = PointToScreen(new Point(e.X + mOffset.X, e.Y + mOffset.Y));
mTargetPoint = mCurrentPoint;
mTimer.Enabled = true;
}
这个事件：
protected override void OnMouseMove(MouseEventArgs e)
{
mTargetPoint = PointToScreen(new Point(e.X + mOffset.X, e.Y + mOffset.Y));
mTimer.Enabled = true;
}
如果我只是快速移动鼠标，我就会失去对我正在移动的表格的焦点，并且表格只留下鼠标移动。
但是，如果我单击鼠标按下按钮，然后移动鼠标，快速表格一直处于焦点。
所以我尝试将OnMouseDown事件中的两行复制到OnMouseMove事件：
mOffset = new Point(Width / 2 - e.X, Height / 2 - e.Y);
mTargetPoint = mCurrentPoint;
但是，一旦我将这两行移动到Move事件，就没有任何事情发生。无论我做什么，表格根本不会移动。
如果需要，那么这就是完整的表单代码：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;
using System.IO;
using System.Drawing.Imaging;
namespace Magnifier20070401
{
public partial class MagnifierForm : Form
{
public MagnifierForm()//Configuration configuration, Point startPoint)
{
InitializeComponent();
//--- My Init ---
//mConfiguration = configuration;
FormBorderStyle = FormBorderStyle.None;
ShowInTaskbar = false;//mConfiguration.ShowInTaskbar;
TopMost = true;//mConfiguration.TopMostWindow;
Width = 150;// mConfiguration.MagnifierWidth;
Height = 150;// mConfiguration.MagnifierHeight;
// Make the window (the form) circular
GraphicsPath gp = new GraphicsPath();
gp.AddEllipse(ClientRectangle);
Region = new Region(gp);
mImageMagnifier = ScreenVideoRecorder.Properties.Resources.magnifierGlass;
mTimer = new Timer();
mTimer.Enabled = true;
mTimer.Interval = 20;
mTimer.Tick += new EventHandler(HandleTimer);
mScreenImage = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
Screen.PrimaryScreen.Bounds.Height);
mStartPoint = new Point(500, 500);// startPoint;
mTargetPoint = new Point(500, 500); // startPoint;
/*if (mConfiguration.ShowInTaskbar)
ShowInTaskbar = true;
else
ShowInTaskbar = false;*/
}
protected override void OnShown(EventArgs e)
{
RepositionAndShow();
}
private delegate void RepositionAndShowDelegate();
private void RepositionAndShow()
{
if (InvokeRequired)
{
Invoke(new RepositionAndShowDelegate(RepositionAndShow));
}
else
{
// Capture the screen image now!
Graphics g = Graphics.FromImage(mScreenImage);
g.CopyFromScreen(0, 0, 0, 0, new Size(mScreenImage.Width, mScreenImage.Height));
g.Dispose();
//if (mConfiguration.HideMouseCursor)
// Cursor.Hide();
//else
Cursor = Cursors.Cross;
Capture = true;
/*if (mConfiguration.RememberLastPoint)
{
mCurrentPoint = mLastMagnifierPosition;
Cursor.Position = mLastMagnifierPosition;
Left = (int)mCurrentPoint.X - Width / 2;
Top = (int)mCurrentPoint.Y - Height / 2;
}
else
{*/
mCurrentPoint = Cursor.Position;
//}
Show();
}
}
void HandleTimer(object sender, EventArgs e)
{
float dx = /*mConfiguration.SpeedFactor*/ (float)0.35 * (mTargetPoint.X - mCurrentPoint.X);
float dy = /*mConfiguration.SpeedFactor*/ (float)0.35 * (mTargetPoint.Y - mCurrentPoint.Y);
if (mFirstTime)
{
mFirstTime = false;
mCurrentPoint.X = mTargetPoint.X;
mCurrentPoint.Y = mTargetPoint.Y;
Left = (int)mCurrentPoint.X - Width / 2;
Top = (int)mCurrentPoint.Y - Height / 2;
return;
}
mCurrentPoint.X += dx;
mCurrentPoint.Y += dy;
if (Math.Abs(dx) < 1 && Math.Abs(dy) < 1)
{
mTimer.Enabled = false;
}
else
{
// Update location
Left = (int)mCurrentPoint.X - Width / 2;
Top = (int)mCurrentPoint.Y - Height / 2;
mLastMagnifierPosition = new Point((int)mCurrentPoint.X, (int)mCurrentPoint.Y);
}
Refresh();
}
protected override void OnMouseDown(MouseEventArgs e)
{
mOffset = new Point(Width / 2 - e.X, Height / 2 - e.Y);
mCurrentPoint = PointToScreen(new Point(e.X + mOffset.X, e.Y + mOffset.Y));
mTargetPoint = mCurrentPoint;
mTimer.Enabled = true;
}
protected override void OnMouseUp(MouseEventArgs e)
{
//if (mConfiguration.CloseOnMouseUp)
//{
/* Close();
mScreenImage.Dispose();
//}
Cursor.Show();
Cursor.Position = mStartPoint; */
}
protected override void OnMouseMove(MouseEventArgs e)
{
//if (e.Button == MouseButtons.Left)
//{
mOffset = new Point(Width / 2 - e.X, Height / 2 - e.Y);
mTargetPoint = PointToScreen(new Point(e.X + mOffset.X, e.Y + mOffset.Y));
//mTargetPoint = mCurrentPoint;
mTimer.Enabled = true;
//}
}
protected override void OnPaintBackground(PaintEventArgs e)
{
/*if (mConfiguration.DoubleBuffered)
{
// Do not paint background (required for double buffering)!
}
else
{
base.OnPaintBackground(e);
}*/
base.OnPaintBackground(e);
}
protected override void OnPaint(PaintEventArgs e)
{
if (mBufferImage == null)
{
mBufferImage = new Bitmap(Width, Height);
}
Graphics bufferGrf = Graphics.FromImage(mBufferImage);
Graphics g;
/*if (mConfiguration.DoubleBuffered)
{
g = bufferGrf;
}
else
{*/
g = e.Graphics;
//}
if (mScreenImage != null)
{
Rectangle dest = new Rectangle(0, 0, Width, Height);
int w = (int)(Width / 3.0);//mConfiguration.ZoomFactor);
int h = (int)(Height / 3.0);//mConfiguration.ZoomFactor);
int x = Left - w / 2 + Width / 2;
int y = Top - h / 2 + Height / 2;
g.DrawImage(
mScreenImage,
dest,
x, y,
w, h,
GraphicsUnit.Pixel);
}
if (mImageMagnifier != null)
{
g.DrawImage(mImageMagnifier, 0, 0, Width, Height);
}
//if (mConfiguration.DoubleBuffered)
//{
e.Graphics.DrawImage(mBufferImage, 0, 0, Width, Height);
//}
}
//--- Data Members ---
#region Data Members
private Timer mTimer;
private Configuration mConfiguration;
private Image mImageMagnifier;
private Image mBufferImage = null;
private Image mScreenImage = null;
private Point mStartPoint;
private PointF mTargetPoint;
private PointF mCurrentPoint;
private Point mOffset;
private bool mFirstTime = true;
private static Point mLastMagnifierPosition = Cursor.Position;
#endregion
private void MagnifierForm_KeyDown(object sender, KeyEventArgs e)
{
if (e.Control && e.KeyCode.ToString() == "M")
{
this.Close();
}
}
}
}
在Form1中，我只为表单创建一个新实例，然后我可以移动它。 为什么在没有按下鼠标时快速移动鼠标会失去焦点呢？
答案 0 :(得分：2)
在您的MouseDown中，您应该将this.Capture = true;放入您的MouseUp中this.Capture.false;
如果您快速移动鼠标，它可能会移动到窗口外，默认情况下，只有鼠标所在的窗口才会显示鼠标消息。使用Control.Capture修复了该问题。
答案 1 :(得分：2)
这不是一个事件，它是一种方法。并且您没有获得默认行为（捕获鼠标），因为您忘记调用base.OnMouseDown（）。 MSDN库严厉警告：
对继承者的说明：
当在派生类中重写OnMouseDown时， 一定要调用基类的OnMouseDown方法以便注册 代表们会收到这个活动。
好吧，以及基类方法所做的其他事情。就像捕捉鼠标一样。当你真正知道自己在做什么时，才跳过调用基类方法。这很难弄明白，你真的需要知道基类方法的作用。 不总是只有触发事件一样简单。通常，类越精细，它就越有可能将基本方法中的某些代码抛弃。 DataGridView是松鼠之王。您可以从参考源获取该信息。
只需在方法底部添加此行即可解决您的问题：
base.OnMouseDown(e);
在OnMouseMove（）覆盖中执行相同的操作。不是因为这是解决这个特定问题所必需的，因为文档说你应该这样做。