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TTreeView? How it works?

Posted on 1997-12-09
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Last Modified: 2010-04-04
I have no clue on how the TTreeView works... I've looked into Delphi2, Secrets of Delphi2, Delphi Programming for Dummies and I've also looked into the Delpi on line help with little to know results.  HELP!!!!!  Need info. on all area of TTreeView.
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Question by:PPaul
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JimBob091197 earned 200 total points
ID: 1353257
Delphi's TTreeView (which is a BIG improvement over Delphi 1's TOutline component) has a property "Items" of type TTreeNodes.  Most of the work is done with the items property.

Consider the following:
(Form1 has a TTreeView called tv.)

procedure TForm1.AddSomeNodes;
var
    RootNode, Child1Node, Child2Node, GrandChildNode: TTreeNode;
begin
    RootNode := tv.Items.AddChild(nil, 'This is the root');
    Child1Node := tv.Items.AddChild(RootNode, 'This is a child');
    Child2Node := tv.Items.AddChild(RootNode, 'Second child');
    GrandChildNode := tv.Items.AddChild(Child1Node, 'Child of Child 1');
end;

From this you can see that to add a tree node you write:
    MyNewNode := tv.Items.AddChild(ParentNode, 'Caption');
If ParentNode = nil then the item is added to the root of the tree.

Each node in the treeview is of type TTreeNode.  TreeNode has some useful methods, e.g. Expand, Collapse, GetFirstChild, HasAsParent, etc.

If you run the procedure AddSomeNodes above, you will see that RootNode is collapsed.  To expand it with code, call "RootNode.Expand(False);".  To expand the node AND all its children nodes, call "ANode.Expand(True);".  To collapse the node again, call "ANode.Collapse;".

To go through the immediate children of any node, do the following: (This code goes through all the children of the selected node):
procedure TForm1.ShowSelectedChildren;
var
  ParentNode, ChildNode: TTreeNode;
begin
  ParentNode := tv.Selected;
  if (ParentNode <> nil) then begin
    ChildNode := ParentNode.GetFirstChild;
    while (ChildNode <> nil) do begin
      ShowMessage(ChildNode.Text);
      ChildNode := ChildNode.GetNextSibling;
    end;
  end;
end;


Assigning images to a TTreeView is similar to Delphi's TListView.  Put a TImageList on the form and add a few bitmaps/icons to it.  Set the treeview's Images property to the imagelist.  When you add a TreeNode you can set its ImageIndex and SelectedIndex properties.  The ImageIndex property determines which image in the TImageList the node will use when it is not selected.  The SelectedIndex property determines which image the node will use when it is selected.

E.g.
MyNewNode := tv.Items.AddChild(ParentNode, 'New Node');
MyNewNode.ImageIndex := 5;
MyNewNode.SelectedIndex := 5;

To change the display text of a node:
MyNode.Text := 'Some new caption';

Other useful properties of the TTreeView are ReadOnly (user cannot edit a node's text),  ShowButtons and ShowLines (determine whether lines connecting nodes are shown.  If you open any Windows 95 help file with a contents you will see that the contents is a treeview with ShowButtons = False and ShowLines = False).

This should get you started.  Let me know if I can be of more help.

JB
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Author Comment

by:PPaul
ID: 1353258
You make it easy to understand....  The above code for serching throught a nods child how do I do it without the selected part?

P.S.  I have also unlocked the How to hide a form on start-up...
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LVL 5

Expert Comment

by:JimBob091197
ID: 1353259
All the nodes are of type TTreeNode.  I use tv.Selected to get one TTreeNode.  To search through a node's children without using the selected part, you could use variables to store each node you add (e.g. ANode := tv.Items.AddChild(SomeParentNode, 'A Node');) or you could go through the items until you found the node you wanted (e.g. for i := 0 to tv.Items.Count - 1 do if tv.Items[i].Text = 'Some Node Text' then ...)

Either way, you would have to get a TTreeNode to work with.  Once you have a TTreeNode you can use that node to go through its children nodes.

JB
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Author Comment

by:PPaul
ID: 1353260
Thanks JimBob.... If I have anymore questions about TTreeView can I get you E-Mail Address....

Here's Mine.   920595@ican.net...

thanks...
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LVL 5

Expert Comment

by:JimBob091197
ID: 1353261
Sorry about the delay - I've been away for a couple of weeks.

My e-mail address is davekw@iafrica.com.
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