In a basic tree list, the nodes are just text. It is also possible to have the nodes associated with objects or records (ie, they can store a pointer).

Each node has 2 index numbers - one absolute and one relative to its parent node. When new nodes are added, or existing nodes are deleted, the indices of the other nodes change accordingly.

Component	Property	Comments
TTreeView	Items	TTreeNodes object - main access to nodes cnt := TreeView1.Items.Count; SomeNode := TreeView1.Items[5]; // Zero based access // 0 to Count-1
	Selected	Use this to access or set the currently selected node. If the RightClickSelect property is True, this may differ from the node that is highlighted to indicate selection.
	RightClickSelect	When True, it causes the Selected property to change when a node is right clicked - default=False
	HideSelection	When True, the highlight is hidden when focus move to another control; when False, the node always appears selected - default=True
	ShowButtons	Controls display of the +/- buttons - default=True
	ShowLines	Controls display of lines that link child nodes to their corresponding parent nodes - default=True
	Indent	Specifies the number of pixels child nodes are indented - default=19
TTreeNodes	Count	The number of nodes
	Item	Used to access to a node by its position. Zero is the first node. FirstNode := TreeView1.Items.Item[0]; can be written FirstNode := TreeView1.Items[0]; Very slow to use.
TTreeNode	Text	What is displayed
	Level	Level of indentation of this node within the tree view control - zero is the top
	Data	Points to an object or record PMyRec(TreeView1.Selected.Data)^.FName
	Selected	Boolean - True for the currently selected node
	Focused	Controls the node's appearance - I can't make setting this do anything

Component	Method	Comments
TTreeView	OnCompare	Use this to provide a non-alphabetic sort order.
	OnEditing	Called before the user edits a node's Text property. Set AllowEdit to False to prevent the user from editing the specified node.
	OnEdited	Called after the user edits a node's Text property. Use this to make the name change permanent - update filename, table field value, etc.
	GetNodeAt(x, y) GetHitTestInfoAt(x, y)	Used with mouse position for drag and drop (see example in the help)
	LoadFromFile, LoadFromStream, SaveToFile, SaveToStream	The data format is not specified. My experiments indicate that only the node text is saved, Tabs are used for level indications. (Not very useful.)
	OnClick, OnDblClick, OnContextPopup, ...	For each of these, there is only one event for the entire tree list, use Selected to get the node. procedure TForm1.TreeView1DblClick(Sender: TObject); begin Edit1.Text := TreeView1.Selected.Text; end;
TTreeNodes	AddChildFirst, AddChild, AddChildObjectFirst, AddChildObject, AddFirst, Add, AddObjectFirst, AddObject, Insert	Used to add nodes I see no difference between Add and AddChild.
	BeginUpdate EndUpdate	Use BeginUpdate to prevent screen repaints and to speed up your code while adding nodes to the tree view. Use EndUpdate to update the screen.
TTreeNode	EditText	Allows the user to modify the displayed text. OnEditing is called before the node is placed in edit mode. OnEdited is called if the value is changed. (Esc cancels the change.) TreeView1.Items [3].Selected := true; TreeView1.Items [3].EditText;
	GetNext	Returns the next node including nodes that aren't visible and child nodes.
	GetNextSibling	Returns the next node in the tree view at the same level as the calling node, regardless of whether it's visible.
	GetNextVisible	Returns the next visible node in the tree view after the calling node.
	GetFirstChild, GetNextChild, GetPrevChild	Locate a node in the list of immediate children of the tree view node.

TTreeNodes.Add

How to add just the text labels

TTreeNodes.Count
TTreeNode.Data

Very good example showing how to associate records with a tree view - add to currently selected node, retrieve data

TCustomTreeView.GetNodeAt

How to use GetNodeAt and GetHitTestInfoAt

TTreeNode.GetNext

TTreeNode.GetNextChild

S I Node text
| |
| ----- Normal/Selected image (changes automatically)
------- State image

C:\Program Files\Common Files\Borland Shared\Images\Icons\

When ImageIndex and SelectedIndex contain different values, the image is automatically changed when you click on (select) that node. (For example, consider the open and closed directory folders in Windows Explorer.)

The State image is intended to show both states of a check box, radio button, and similar state indicators ... however, you may use it for anything you like.

Property	Usage
TCustomTreeView.Images	This should point to an ImageList
TTreeNode.ImageIndex	This selects an image from TCustomTreeView.Images
TTreeNode.SelectedIndex	Specifies the image from TCustomTreeView.Images to display when the tree node is selected
TTreeNode.OverlayIndex	Specifies the image from TCustomTreeView.Images to draw transparently over the current image, for example. an X to indicate "no longer available"
TCustomTreeView.StateImages	This should point to an ImageList
TTreeNode.StateIndex	This selects an image from TCustomTreeView.StateImages
TCustomTreeView.OnGetImageIndex	These can be used to change the image index for a node before it is drawn ... however, since they are called for every node, you must test to determine which node is being passed. If present, keep these simple.
TCustomTreeView.OnGetSelectedIndex

Specific images are selected via the indices

• ImageIndex and SelectedIndex point to Images
• StateIndex points to StateImages

• Create a new application
• On the form, place

   Tab       Component
  Win32      TImageList
  Win32      TTreeView
  

• Set the following properties

  Component	Property	Value	Comments
  TreeView1	Images	ImageList1
  	StateImages	ImageList1

• Double click ImageList1 (that opens a dialog box)
• Click the Add... button
• Select several *.bmp files from

     C:\Program Files\Common Files\Borland Shared\Images\Icons\
  

• Double click TreeView1 (that opens a dialog box)
• Add several nodes - enter Text and 3 indices

• Compile and run
• Open the tree, click several nodes and watch the icons

URL: http:// cpcug.org / user / clemenzi / technical / Languages / Delphi / TreePanel.html