Scroll in treeview

  • Thread starter Thread starter Jeff Johnson
  • Start date Start date
J

Jeff Johnson

hi all, I have a treeview control and for dragdrop operation I need
automatic scroll up or down as needed. Example: when I drag an item over
the superior limit I want to scroll up and when drag far the bottom I want
to scroll down..
Click to expand...

If no one else answers you're question I'll try to find some code I THINK I
have and post it later in the day. (I HOPE I have .NET code for this; I
could be thinking of a VB6 project....)
 
hi all, I have a treeview control and for dragdrop operation I need
automatic scroll up or down as needed. Example: when I drag an item over the
superior limit I want to scroll up and when drag far the bottom I want to
scroll down..
this is my code....I don't know how to do this scroll thing..
public class DragDropTreeview : TreeView
{


private TreeNode srcNodeForDrag;

public DragDropTreeview()
{
this.AllowDrop = true;
}
protected override void OnDragDrop(DragEventArgs e)
{
Point pt = PointToClient(new Point(e.X, e.Y));
TreeNode DestinationNode = this.GetNodeAt(pt);

// Ensure that the list item index is contained in the data.
if (e.Data.GetDataPresent(typeof(TreeNode)))
{
// Perform drag-and-drop, depending upon the effect.
if (e.Effect == DragDropEffects.Copy)
{
TreeNode tmpTN = (TreeNode)srcNodeForDrag.Clone();
DestinationNode.Nodes.Add(tmpTN);
}
else if (e.Effect == DragDropEffects.Move)
{
TreeNode tmpTN = (TreeNode)srcNodeForDrag.Clone();
DestinationNode.Nodes.Add(tmpTN);
srcNodeForDrag.Remove();
}
}
}


protected override void OnDragOver(DragEventArgs e)
{
if ((e.KeyState & 8) == 8 &&
(e.AllowedEffect & DragDropEffects.Copy) ==
DragDropEffects.Copy)
{
// CTL KeyState for copy.
e.Effect = DragDropEffects.Copy;
}
else if ((e.AllowedEffect & DragDropEffects.Move) ==
DragDropEffects.Move)
{
e.Effect = DragDropEffects.Move;
}
}

protected override void OnItemDrag(ItemDragEventArgs e)
{
srcNodeForDrag = (TreeNode)e.Item;
this.DoDragDrop(e.Item, DragDropEffects.All);
}
 
I found the way!!!

Point pt = PointToClient(new Point(e.X, e.Y));
TreeNode DestinationNode = this.GetNodeAt(pt);
DestinationNode.PrevVisibleNode.EnsureVisible();
DestinationNode.NextVisibleNode.EnsureVisible();

in the DragOver Method...

I have own more issue: scroll speed, it just scroll at light speed, and that
is not too user friendly, :), do you know how can I control the speed??
 
I found the way!!!

Point pt = PointToClient(new Point(e.X, e.Y));
TreeNode DestinationNode = this.GetNodeAt(pt);
DestinationNode.PrevVisibleNode.EnsureVisible();
DestinationNode.NextVisibleNode.EnsureVisible();

in the DragOver Method...

I have own more issue: scroll speed, it just scroll at light speed, and
that is not too user friendly, :), do you know how can I control the
speed??
Click to expand...

When you decide you need to scroll, enable a timer and let the scrolling
code happen in the timer event. Then, when the mouse moves out of scroll
range, disable the timer.
 
im trying but it isn't work.....I don't know how pass the dragEventArgs to
the MakeVisible methods
Click to expand...

You can't pass them. Store them in a module-level variable (I guess the .NET
term is "field"; regardless, it's basically a global) and then simply
reference that variable in the timer event handler.
 
im trying but it isn't work.....I don't know how pass the dragEventArgs to
the MakeVisible methods

public class DragDropTreeview : TreeView
{
private TreeNode srcNodeForDrag;
Timer temporizador = new Timer();

public DragDropTreeview()
{
this.AllowDrop = true;
temporizador.Interval = 250;
temporizador.Tick += MakeVisible;
}


protected void MakeVisible(object sender, EventArgs a)
{
DragEventArgs e = a as DragEventArgs;
if (e != null) //_>ALWAYS NULL, HELP HERE
{
Point pt = PointToClient(new Point(e.X, e.Y));
TreeNode DestinationNode = this.GetNodeAt(pt);
DestinationNode.PrevVisibleNode.EnsureVisible();
DestinationNode.NextVisibleNode.EnsureVisible();
}
temporizador.Enabled = false;
}

protected override void OnDragOver(DragEventArgs e)
{

temporizador.Enabled = true;

if ((e.KeyState & 8) == 8 &&
(e.AllowedEffect & DragDropEffects.Copy) ==
DragDropEffects.Copy)
{
// CTL KeyState for copy.
e.Effect = DragDropEffects.Copy;
}
else if ((e.AllowedEffect & DragDropEffects.Move) ==
DragDropEffects.Move)
{
e.Effect = DragDropEffects.Move;
}

}


protected override void OnDragDrop(DragEventArgs e)
{
Point pt = PointToClient(new Point(e.X, e.Y));
TreeNode DestinationNode = this.GetNodeAt(pt);

// Ensure that the list item index is contained in the data.
if (e.Data.GetDataPresent(typeof(TreeNode)))
{
// Perform drag-and-drop, depending upon the effect.
if (e.Effect == DragDropEffects.Copy)
{
TreeNode tmpTN = (TreeNode)srcNodeForDrag.Clone();
DestinationNode.Nodes.Add(tmpTN);
}
else if (e.Effect == DragDropEffects.Move)
{
TreeNode tmpTN = (TreeNode)srcNodeForDrag.Clone();
DestinationNode.Nodes.Add(tmpTN);
srcNodeForDrag.Remove();
}
}
}


protected override void OnDragOver(DragEventArgs e)
{

temporizador.Enabled = true;

if ((e.KeyState & 8) == 8 &&
(e.AllowedEffect & DragDropEffects.Copy) ==
DragDropEffects.Copy)
{
// CTL KeyState for copy.
e.Effect = DragDropEffects.Copy;
}
else if ((e.AllowedEffect & DragDropEffects.Move) ==
DragDropEffects.Move)
{
e.Effect = DragDropEffects.Move;
}

}

protected override void OnItemDrag(ItemDragEventArgs e)
{
srcNodeForDrag = (TreeNode)e.Item;
this.DoDragDrop(e.Item, DragDropEffects.All);
}
 
I try other approach, use the timer to slow down the things. When is
disabled I do the EnsureVisible for the sibblings nodes. The tick handler
disable the timer and when I call EnsureVisible I enabled the timer. The
interval is 250 miliseconds, so the scroll only occurs at this speed,
:)....thanks for tellme about the timer!!

The Final Working Code is:
public class DragDropTreeview : TreeView
{
#region Fields & Properties
private TreeNode srcNodeForDrag;
Timer temporizador = new Timer();
#endregion

#region Constructors
public DragDropTreeview()
{
this.AllowDrop = true;
temporizador.Interval = 250;
temporizador.Tick += (x, y) => { temporizador.Enabled =
false; };
}
#endregion

protected override void OnDragOver(DragEventArgs e)
{
if (!temporizador.Enabled)
{
Point pt = PointToClient(new Point(e.X, e.Y));
TreeNode DestinationNode = this.GetNodeAt(pt);
DestinationNode.PrevVisibleNode.EnsureVisible();
DestinationNode.NextVisibleNode.EnsureVisible();
temporizador.Enabled = true;
}


if ((e.KeyState & 8) == 8 &&
(e.AllowedEffect & DragDropEffects.Copy) ==
DragDropEffects.Copy)
{
// CTL KeyState for copy.
e.Effect = DragDropEffects.Copy;
}
else if ((e.AllowedEffect & DragDropEffects.Move) ==
DragDropEffects.Move)
{
e.Effect = DragDropEffects.Move;
}

}
..... the rest remains unchanged.
 
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