/// <summary>
/// 在将对象拖出控件的边界时发生。
/// </summary>
/// <param name="e"></param>
protected override void OnDragLeave(EventArgs e)
{
DragHelper.ImageList_DragLeave(this.Handle);
// Disable timer for scrolling dragged item
this._timer.Enabled = false;
base.OnDragLeave(e);
}
/// <summary>
/// 在将对象拖入控件的边界时发生。
/// </summary>
/// <param name="drgevent"></param>
protected override void OnDragEnter(DragEventArgs e)
{
DragHelper.ImageList_DragEnter(this.Handle, e.X - this.Left,
e.Y - this.Top);
// Enable timer for scrolling dragged item
this._timer.Enabled = true;
base.OnDragEnter(e);
}
/// <summary>
/// Begin dragging image
/// 当用户开始拖动节点时，调用此方法
/// 在调用 this.DoDragDrop 之后，还需要调用 DrawEndDrag
/// </summary>
/// <returns></returns>
protected bool DrawOnItemDrag()
{
if (_dragNode == null)
{
return(false);
}
// Reset image list used for drag image
this._imageListDrag.Images.Clear();
this._imageListDrag.ImageSize = new Size(this._dragNode.Bounds.Size.Width + this.Indent, this._dragNode.Bounds.Height);
// Create new bitmap
// This bitmap will contain the tree node image to be dragged
Bitmap bmp = new Bitmap(this._dragNode.Bounds.Width + this.Indent, this._dragNode.Bounds.Height);
// Get graphics from bitmap
Graphics gfx = Graphics.FromImage(bmp);
//gfx.Clear(SystemColors.GradientInactiveCaption);
// Draw node icon into the bitmap
//cxs
//gfx.DrawImage(this.imageListTreeView.Images[0], 0, 0);
if (this.ImageList != null && this._dragNode.ImageIndex < this.ImageList.Images.Count && this._dragNode.ImageIndex >= 0)
{
gfx.DrawImage(this.ImageList.Images[this._dragNode.ImageIndex], 0, 0);
}
// Draw node label into bitmap
gfx.DrawString(this._dragNode.Text,
this.Font,
new SolidBrush(this.ForeColor),
(float)this.Indent, 1.0f);
// Add bitmap to imagelist
this._imageListDrag.Images.Add(bmp);
// Get mouse position in client coordinates
Point p = this.PointToClient(Control.MousePosition);
// Compute delta between mouse position and node bounds
int dx = p.X + this.Indent - this._dragNode.Bounds.Left;
int dy = p.Y - this._dragNode.Bounds.Top;
// Begin dragging image
return(DragHelper.ImageList_BeginDrag(this._imageListDrag.Handle, 0, dx, dy));
}
private void timer_Tick(object sender, EventArgs e)
{
// get node at mouse position
Point pt = PointToClient(Control.MousePosition);
TreeNode node = this.GetNodeAt(pt);
if (node == null)
{
return;
}
// if mouse is near to the top, scroll up
if (pt.Y < 30)
{
// set actual node to the upper one
if (node.PrevVisibleNode != null)
{
node = node.PrevVisibleNode;
// hide drag image
DragHelper.ImageList_DragShowNolock(false);
// scroll and refresh
node.EnsureVisible();
this.Refresh();
// show drag image
DragHelper.ImageList_DragShowNolock(true);
}
}
// if mouse is near to the bottom, scroll down
else if (pt.Y > this.Size.Height - 30)
{
if (node.NextVisibleNode != null)
{
node = node.NextVisibleNode;
DragHelper.ImageList_DragShowNolock(false);
node.EnsureVisible();
this.Refresh();
DragHelper.ImageList_DragShowNolock(true);
}
}
}
/// <summary>
/// 在将对象拖到控件的边界上发生。
/// </summary>
/// <param name="drgevent"></param>
protected override void OnDragOver(DragEventArgs e)
{
// Compute drag position and move image
Point formP = this.PointToClient(new Point(e.X, e.Y));
//DragHelper.ImageList_DragMove(formP.X - this.Left, formP.Y - this.Top);
DragHelper.ImageList_DragMove(formP.X, formP.Y);
// Get actual drop node
TreeNode dropNode = this.GetNodeAt(this.PointToClient(new Point(e.X, e.Y)));
if (dropNode == null)
{
e.Effect = DragDropEffects.None;
return;
}
e.Effect = DragDropEffects.Move;
// if mouse is on a new node select it
if (this._tempDropNode != dropNode)
{
DragHelper.ImageList_DragShowNolock(false);
this.SelectedNode = dropNode;
DragHelper.ImageList_DragShowNolock(true);
_tempDropNode = dropNode;
}
// Avoid that drop node is child of drag node
TreeNode tmpNode = dropNode;
while (tmpNode.Parent != null)
{
if (tmpNode.Parent == this._dragNode)
{
e.Effect = DragDropEffects.None;
}
tmpNode = tmpNode.Parent;
}
base.OnDragOver(e);
}
/// <summary>
/// Unlock updates
/// 在拖放操作完成时发生时，调用此方法
/// </summary>
protected void DrawOnDragDrop()
{
// Unlock updates
DragHelper.ImageList_DragLeave(this.Handle);
}
/// <summary>
/// End dragging image
/// 停止绘制
/// </summary>
protected void DrawEndDrag()
{
DragHelper.ImageList_EndDrag();
}