Can anybody tell me how to do the following:
- Create Nodes
- Enable/Disable Individual Nodes
I want to know how to do the above at Application run-time, eg in the Form's OnCreate event.
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3 Answers
@Remus, here you have an simple example adding nodes.
Adding a root Node (level 0)
Var
Node : TTreeNode;
begin
//function TTreeNodes.Add(Sibling: TTreeNode; const S: string): TTreeNode;
Node:=TreeView1.Items.Add(nil,'My Root Node') ;
Node.ImageIndex:=0;//now you can change any property of the node
end;
Adding a child Node (level > 0)
//in this case we add a child node in the current selected node.
Var
Node : TTreeNode;
begin
if TreeView1.Selected= nil then exit;
Node:=TreeView1.Items.AddChild(TreeView1.Selected,'My Child Node') ;
Node.ImageIndex:=0;//now you can change any property of the node
end;
Adding many nodes
if you wanna add many nodes using a loop or something else you must use BeginUpdate before making the changes to the treeview. When all changes are complete, call EndUpdate to show the changes on screen. BeginUpdate and EndUpdate prevent excessive redraws and speed up processing time when nodes are added, deleted, or inserted.
Var
Node : TTreeNode;
i : Integer;
begin
TreeView1.Items.BeginUpdate;
try
for i:=1 to 100 do
begin
Node:=TreeView1.Items.Add(nil,'My Root Node '+IntToStr(i)) ;
Node.ImageIndex:=0;
end;
finally
TreeView1.Items.EndUpdate;
end;
end;
About disable a node, does not exist any property like that.
Comments
Adding nodes:
function FindRootNode(ACaption: String; ATreeView: TTreeView): TTreeNode;
var LCount: Integer;
begin
result := nil;
LCount := 0;
while (LCount < ATreeView.Items.Count) and (result = nil) do
begin
if (ATreeView.Items.Item[LCount].Text = ACaption) and (ATreeView.Items.Item[LCount].Parent = nil) then
result := ATreeView.Items.Item[LCount];
inc(LCount);
end;
end;
...
var LDestNode: TTreeNode;
begin
LDestNode := FindRootNode('category', TreeView1);
if LDestNode <> nil then
begin
TreeView1.Items.AddChild(LDestNode, 'node1');
TreeView1.Items.AddChild(LDestNode, 'node2');
end;
end;
(see also http://msdn.microsoft.com/en-us/library/70w4awc4.aspx)
Disabeling a node
As far as I know, there is no way to disable a TreeNode. Only thing you could do is intercept the beforeSelect-event and cancel the selection there. Not so nice.
4 Comments
Mark Wilkins
There is a "Selectable" property that exists in TCustomViewItem, which the Item property descends from. That might behave as a kind of disabling mechanism.
Remus Rigo
i know how selectable works, but I want to do this in MainForm.OnCreate event
Sertac Akyuz
@Mark: In what version of Delphi is this "TCustomViewItem"? I cannot find it. @Remus: Does that mean you're trying to avoid event handlers. Otherwise you could populate a "disabled nodes" list or array in form's OnCreate and check against these items on OnChanging and OnCustomDrawItem of the TreeView. OTOH there's a TVIS_EX_DISABLED flag for Shell Controls > ver. 6.00 (Vista?), but all it really does is to draw the text with the disabled color and not to draw the selected look if you click on it. The item, in fact, is selected.
Mark Wilkins
@Sertac: I was looking at the Delphi 7 help file.
You can disable selection in OnChanging event handler. This is event of TTreeView.
procedure TForm.OnChanging(Sender: TObject; Node: TTreeNode; var AllowChange: Boolean);
begin
AllowChange := CheckSomePropertiesOfNode(Node);
end;
