对窗体加越界限制后，鼠标拖动窗体越界时，窗体不能动，鼠标位置可动，但窗体不再越界时，鼠标位置还能回到鼠标按下时相对窗体的坐标：
1、首先创建一个窗体Form1，然后在窗体上拖一个button1按钮（主要通过这个按钮来拖动窗体）
2、然后对按钮添加鼠标按下事件、鼠标移动事件和鼠标抬起事件，事件里面是对窗体和鼠标坐标的操作，整体代码如下：
using System.Drawing;
using System.Windows.Forms;
namespace 窗体越界鼠标还能回到初始坐标
{
public partial class Form1 : System.Windows.Forms.Form
{
#region 变量定义
public Point mainFormPosition;//主窗口左上角位置
int workingAreaHeight = SystemInformation.WorkingArea.Height;
int workingAreaWidth = SystemInformation.WorkingArea.Width;
private Point relativetMousePosition;//鼠标相对窗体的相对坐标
bool FirstLeft = false;//是否左边第一次按下时坐标
bool FirstRight = false;//是否右边第一次按下时坐标
bool FirstUp = false;//是否上边第一次按下时坐标
bool FirstDown = false;//是否下边第一次按下时坐标
bool isFirstDown = true;//是否第一次按下，鼠标越界纠正时判断是否是第一次按下，不是按下后又拖动了
bool isMoveOut = false;//是否拖出
//这两个变量做差，差值为拖出的距离时软件弹出侧边
int oldMove_X = 0;//侧边停靠拖出时起始坐标
//上一个时刻、鼠标的位置
private Point oldMousePosition;
//当前时刻、鼠标的位置
private Point currentMousePosition;
//鼠标事件
[System.Runtime.InteropServices.DllImport("user32")]
private static extern int mouse_event(int dwFlags, int dx, int dy, int cButtons, int dwExtraInfo);
//移动鼠标
const int MOUSEEVENTF_MOVE = 0x0001;
//模拟鼠标左键按下
const int MOUSEEVENTF_LEFTDOWN = 0x0002;
//模拟鼠标左键抬起
const int MOUSEEVENTF_LEFTUP = 0x0004;
//模拟鼠标右键按下
const int MOUSEEVENTF_RIGHTDOWN = 0x0008;
//模拟鼠标右键抬起
const int MOUSEEVENTF_RIGHTUP = 0x0010;
//模拟鼠标中键按下
const int MOUSEEVENTF_MIDDLEDOWN = 0x0020;
//模拟鼠标中键抬起
const int MOUSEEVENTF_MIDDLEUP = 0x0040;
//标示是否采用绝对坐标
const int MOUSEEVENTF_ABSOLUTE = 0x8000;
#endregion
#region 窗体初始化
public Form1()
{
InitializeComponent();
}
#endregion
//-------------------------按钮button1鼠标事件---------------------------------------------------------------
#region 鼠标左键按下Button1按钮事件
private void Button1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
currentMousePosition = Control.MousePosition;
oldMousePosition = currentMousePosition; //鼠标按下时、两个时刻的坐标变成一样，防止错误移动
mainFormPosition = Location;
if (isFirstDown)//鼠标按下时，记录第一次鼠标按下相对主窗体的坐标
{
relativetMousePosition.X = currentMousePosition.X - Location.X;
relativetMousePosition.Y = currentMousePosition.Y - Location.Y;
isFirstDown = false;
}
if (isMoveOut)//鼠标按下时，记录拖出时的初始坐标
{
oldMove_X = currentMousePosition.X;
}
}
}
#endregion
#region 鼠标左键按住Button1按钮移动事件
private void Button1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
currentMousePosition = Control.MousePosition;
if (currentMousePosition.X < relativetMousePosition.X && currentMousePosition.Y > relativetMousePosition.Y && currentMousePosition.Y < workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y)//左边窗体越界坐标纠正
{
mainFormPosition.X = 0;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition.Y = currentMousePosition.Y;
FirstLeft = true;
}
else if (currentMousePosition.X > workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X && currentMousePosition.Y > relativetMousePosition.Y && currentMousePosition.Y < workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y)//右边窗体越界坐标纠正
{
mainFormPosition.X = workingAreaWidth - this.ClientSize.Width;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition.Y = currentMousePosition.Y;
FirstRight = true;
}
else if (currentMousePosition.Y < relativetMousePosition.Y && currentMousePosition.X > relativetMousePosition.X && currentMousePosition.X < workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X)//上边窗体越界坐标纠正
{
mainFormPosition.Y = 0;
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
//保存上一个时刻的鼠标位置
oldMousePosition.X = currentMousePosition.X;
FirstUp = true;
}
else if (currentMousePosition.Y > workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y && currentMousePosition.X > relativetMousePosition.X && currentMousePosition.X < workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X)//下边窗体越界坐标纠正
{
mainFormPosition.Y = workingAreaHeight - this.ClientSize.Height;
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
//保存上一个时刻的鼠标位置
oldMousePosition.X = currentMousePosition.X;
FirstDown = true;
}
else if (currentMousePosition.X < relativetMousePosition.X && currentMousePosition.Y < relativetMousePosition.Y)//左上角窗体越界坐标纠正
{
mainFormPosition.X = 0;
mainFormPosition.Y = 0;
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition.X = currentMousePosition.X;
oldMousePosition.Y = currentMousePosition.Y;
FirstLeft = true;
FirstUp = true;
}
else if (currentMousePosition.X > workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X && currentMousePosition.Y < relativetMousePosition.Y)//右上角窗体越界坐标纠正
{
mainFormPosition.X = workingAreaWidth - this.ClientSize.Width;
mainFormPosition.Y = 0;
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition.X = currentMousePosition.X;
oldMousePosition.Y = currentMousePosition.Y;
FirstRight = true;
FirstUp = true;
}
else if (currentMousePosition.X < relativetMousePosition.X && currentMousePosition.Y > workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y)//左下角窗体越界坐标纠正
{
mainFormPosition.X = 0;
mainFormPosition.Y = workingAreaHeight - this.ClientSize.Height;
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition.X = currentMousePosition.X;
oldMousePosition.Y = currentMousePosition.Y;
FirstLeft = true;
FirstDown = true;
}
else if (currentMousePosition.X > workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X && currentMousePosition.Y > workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y)//右下角窗体越界坐标纠正
{
mainFormPosition.Y = workingAreaHeight - this.ClientSize.Height;
mainFormPosition.X = workingAreaWidth - this.ClientSize.Width;
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition.X = currentMousePosition.X;
oldMousePosition.Y = currentMousePosition.Y;
FirstRight = true;
FirstDown = true;
}
if (FirstLeft)
{
currentMousePosition.X = relativetMousePosition.X;
FirstLeft = false;
}
if (FirstRight)
{
currentMousePosition.X = workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X;
FirstRight = false;
}
if (FirstUp)
{
currentMousePosition.Y = relativetMousePosition.Y;
FirstUp = false;
}
if (FirstDown)
{
currentMousePosition.Y = workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y;
FirstDown = false;
}
if (FirstLeft && FirstUp)
{
currentMousePosition.X = relativetMousePosition.X;
currentMousePosition.Y = relativetMousePosition.Y;
FirstLeft = false;
FirstUp = false;
}
if (FirstRight && FirstUp)
{
currentMousePosition.X = workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X;
currentMousePosition.Y = relativetMousePosition.Y;
FirstUp = false;
FirstRight = false;
}
if (FirstLeft && FirstDown)
{
currentMousePosition.X = relativetMousePosition.X;
currentMousePosition.Y = workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y;
FirstLeft = false;
FirstDown = false;
}
if (FirstRight && FirstDown)
{
currentMousePosition.X = workingAreaWidth - this.ClientSize.Width + relativetMousePosition.X;
currentMousePosition.Y = workingAreaHeight - this.ClientSize.Height + relativetMousePosition.Y;
FirstRight = false;
FirstDown = false;
}
//对窗体进行移动
mainFormPosition.X += currentMousePosition.X - oldMousePosition.X;
mainFormPosition.Y += currentMousePosition.Y - oldMousePosition.Y;
//保存上一个时刻的鼠标位置
oldMousePosition = currentMousePosition;
#region 越界处理
if (mainFormPosition.X < 0)//左边越界
{
mainFormPosition.X = 0;
}
else if (mainFormPosition.Y < 0)//上边越界
{
mainFormPosition.Y = 0;
}
else if (mainFormPosition.X > workingAreaWidth - this.ClientSize.Width)//右边越界
{
mainFormPosition.X = workingAreaWidth - this.ClientSize.Width;
}
else if (mainFormPosition.Y > workingAreaHeight - this.ClientSize.Height)//下边越界
{
mainFormPosition.Y = workingAreaHeight - this.ClientSize.Height;
}
//更新主窗口位置
Location = mainFormPosition;
#endregion
}
}
#endregion
#region 鼠标在按钮Button1抬起事件
private void Button1_MouseUp(object sender, MouseEventArgs e)
{
isFirstDown = true;
//如果主窗体在这个位置，就判断允许主窗体在鼠标抬起后执行移动事件
if (mainFormPosition.X == workingAreaWidth - this.ClientSize.Width)
{
isMoveOut = false;
}
if (mainFormPosition.X == 0)
{
isMoveOut = false;
}
}
#endregion
}
}
动画效果如下：
这是本人在一个项目中遇到的问题，所以特意总结出来分享给大家。