Virtual TreeView Loop

Question

I would like to go through ALL the roots of a VirtualTreeView and delete them.

I don't want to clear it.

I get an access violation with this code:

var
 Node : PVirtualNode;
begin
 if VirtualStringTree1.GetFirst = NIL then exit;
 Node := NIL;
 repeat
  if Node = NIL then 
   Node := VirtualStringTree1.GetLast 
  else Node:=VirtualStringTree1.GetPrevious (Node);
  if Node <> NIL then VirtualStringTree1.DeleteNode(Node);
 until Node = VirtualStringTree1.GetFirst;
end;

Thank you for your help.

What's the difference between clearing the list and deleting all the nodes? — David Heffernan, Jul 13 '12 at 10:08
rootnodecount := 0 sounds good too. The difference is that I need some of the data from the root nodes BEFORE I delete them. — Ben, Jul 13 '12 at 16:29

score 10 · Accepted Answer · answered Jul 13 '12 at 07:50

10

You have a logical error in your implementation: after deleting the node your local variable Node points to a non-existing node.

I don't understand why you don't want to just clear the tree, but you could delete all nodes from last to first like this:

var
  Node, TmpNode: PVirtualNode;
begin
  Node := Tree.GetLast;
  while Assigned(Node) do
  begin
    TmpNode := Tree.GetPrevious(Node);
    Tree.DeleteNode(Node);
    Node := TmpNode;
  end;
end;

answered Jul 13 '12 at 07:50

Ondrej Kelle

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this works like a charm thank you. you're right I totally forgot about that. – Ben Jul 13 '12 at 07:53

Virtual TreeView Loop

1 Answers1