自訂控制項的拖動

//添加事件
this.MouseUp += new System.Windows.Forms.MouseEventHandler(this.DragEnd);
this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.DragMove);
this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.DragBegin);

private Point p1;//拖動前滑鼠的螢幕座標
private Point p2;//拖動後滑鼠的螢幕座標
private bool _isDrag;//是否正在被拖動
private bool _allowDragMove;
/// <summary>
/// 是否允許被拖動。
/// </summary>
public bool AllowDragMove
{
get
{
return this._allowDragMove;
}
set
{
this._allowDragMove = value;
}
}

private void DragBegin(object sender, System.Windows.Forms.MouseEventArgs e)
{
if(e.Button == MouseButtons.Left & this.AllowDragMove)
{
this._isDrag = true;

//記錄下拖動前的座標
this.p1 = this.PointToScreen(new Point(e.X, e.Y));
}
}

private void DragEnd(object sender, System.Windows.Forms.MouseEventArgs e)
{
if(e.Button == MouseButtons.Left & this._isDrag)
{
this._isDrag = false;

//記錄下拖動後的座標
this.p2 = this.PointToScreen(new Point(e.X, e.Y));
//計算位移
int x = p2.X - p1.X;
int y = p2.Y - p1.Y;

//行動控制項位置
this.Left += x;
this.Top += y;
}
}

private void DragMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
if(this._isDrag)
{
//記錄下拖動後的座標
this.p2 = this.PointToScreen(new Point(e.X, e.Y));
//計算位移
int x = p2.X - p1.X;
int y = p2.Y - p1.Y;

//行動控制項位置
this.Left += x;
this.Top += y;

//把拖動後的頂點作為新的拖動前頂點
p1 = p2;
}
}