接着我们需要实现MouseDown、MouseMove、MouseUp三个事件。
不过在此之前，我们必须要弄清楚，移动即表示坐标的改变，所以必定要有个起始坐标和终点坐标。
所以我们在MoveControl类中加入两个字段。
private Point pPoint; //上个鼠标坐标 private Point cPoint; //当前鼠标坐标
而且在开始拖动之前，我们肯定需要先单击一次控件。在MouseDown时获取当前光标的位置，保存到pPoint中。
（此处用Cursor获得坐标的好处，就是忽略掉容器的麻烦问题）
/// <summary>
/// 鼠标单击事件：用来显示边框
/// </summary>
void MouseClick(object sender, MouseEventArgs e)
{
pPoint = Cursor.Position;
}
接着便实现MouseMove的事件，当鼠标左键按下时，接着移动鼠标后，继续鼠标移动后的坐标，然后与MouseDown时记下的坐标相减，就得到鼠标的位移值，接着控件的Location加上该位移值即可，然后更新pPoint。
/// <summary>
/// 鼠标移动事件：让控件跟着鼠标移动
/// </summary>
void MouseMove(object sender, MouseEventArgs e)
{
Cursor.Current = Cursors.SizeAll; //当鼠标处于控件内部时，显示光标样式为SizeAll
//当鼠标左键按下时才触发
if (e.Button == MouseButtons.Left)
{
cPoint = Cursor.Position; //获得当前鼠标位置
int x = cPoint.X - pPoint.X;
int y = cPoint.Y - pPoint.Y;
currentControl.Location = new Point(currentControl.Location.X + x, currentControl.Location.Y + y);
pPoint = cPoint;
}
}
由于此时还没涉及到边框，所以MouseUp暂时不用处理。至此拖动的基本功能已经实现！
目前MoveControl的完整代码如下：
MoveControl
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
namespace DragControl
{
public class MoveControl
{
#region Constructors
public MoveControl(Control ctrl)
{
currentControl = ctrl;
AddEvents();
}
#endregion
#region Fields
private Control currentControl; //传入的控件
private Point pPoint; //上个鼠标坐标
private Point cPoint; //当前鼠标坐标
#endregion
#region Properties
#endregion
#region Methods
/// <summary>
/// 挂载事件
/// </summary>
private void AddEvents()
{
currentControl.MouseDown += new MouseEventHandler(MouseDown);
currentControl.MouseMove += new MouseEventHandler(MouseMove);
currentControl.MouseUp += new MouseEventHandler(MouseUp);
}
/// <summary>
/// 绘制拖拉时的黑色边框
/// </summary>
public static void DrawDragBound(Control ctrl)
{
ctrl.Refresh();
Graphics g = ctrl.CreateGraphics();
int width = ctrl.Width;
int height = ctrl.Height;
Point[] ps = new Point[5]{new Point(0,0),new Point(width -1,0),
new Point(width -1,height -1),new Point(0,height-1),new Point(0,0)};
g.DrawLines(new Pen(Color.Black), ps);
}
#endregion
#region Events
/// <summary>
/// 鼠标按下事件：记录当前鼠标相对窗体的坐标
/// </summary>
void MouseDown(object sender, MouseEventArgs e)
{
pPoint = Cursor.Position;
}
/// <summary>
/// 鼠标移动事件：让控件跟着鼠标移动
/// </summary>
void MouseMove(object sender, MouseEventArgs e)
{
Cursor.Current = Cursors.SizeAll; //当鼠标处于控件内部时，显示光标样式为SizeAll
//当鼠标左键按下时才触发
if (e.Button == MouseButtons.Left)
{
MoveControl.DrawDragBound(this.currentControl);
cPoint = Cursor.Position; //获得当前鼠标位置
int x = cPoint.X - pPoint.X;
int y = cPoint.Y - pPoint.Y;
currentControl.Location = new Point(currentControl.Location.X + x, currentControl.Location.Y + y);
pPoint = cPoint;
}
}
/// <summary>
/// 鼠标弹起事件：让自定义的边框出现
/// </summary>
void MouseUp(object sender, MouseEventArgs e)
{
this.currentControl.Refresh();
}
#endregion
}
}
