Node Selection

Learn how to select and work with selected nodes in TeeTree

Overview

TeeTree provides comprehensive support for node selection, including single and multiple node selection, programmatic selection, and selection events.

Selecting Nodes Programmatically

Select a Single Node

// Select a specific node
MyNode.Selected := True;

// Clear previous selections first
Tree1.Selected.Clear;
MyNode.Selected := True;

Select All Nodes

// Select all nodes in the tree
Tree1.Selected.SelectAll;

Clear Selection

// Clear all selected nodes
Tree1.Selected.Clear;

Working with Selected Nodes

Access the First Selected Node

// Get the first selected node
if Assigned(Tree1.Selected.First) then
begin
  // Work with the selected node
  Tree1.Selected.First.Text.Text := 'Updated text';
end;

Iterate Through Selected Nodes

var
  i: Integer;
  Node: TTreeNodeShape;
begin
  // Loop through all selected nodes
  for i := 0 to Tree1.Selected.Count - 1 do
  begin
    Node := Tree1.Selected[i];
    // Process each selected node
  end;
end;

Selection Events

TeeTree provides events to respond to selection changes:

OnSelectShape Event

Triggered when a node is selected:

procedure TForm1.Tree1SelectShape(Sender: TTreeNodeShape);
begin
  // Enable buttons when a node is selected
  ButtonAddChild.Enabled := True;
  ButtonAddBrother.Enabled := True;
  ButtonDelete.Enabled := True;
  
  // Show node information
  Label1.Caption := 'Selected: ' + Sender.Text.Text;
end;

OnUnSelectShape Event

Triggered when a node is unselected:

procedure TForm1.Tree1UnSelectShape(Sender: TTreeNodeShape);
begin
  // Disable buttons when no node is selected
  ButtonAddChild.Enabled := False;
  ButtonAddBrother.Enabled := False;
  ButtonDelete.Enabled := False;
end;

Selection Properties

Check if a Node is Selected

if MyNode.Selected then
  ShowMessage('Node is selected');

Get Selection Count

Label1.Caption := 'Selected nodes: ' + IntToStr(Tree1.Selected.Count);

Check if Any Node is Selected

if Tree1.Selected.Count > 0 then
  // At least one node is selected
  ProcessSelection;

Multiple Selection

TeeTree supports multiple node selection:

// Enable multiple selection (typically done at design time or in FormCreate)
Tree1.MultiSelect := True;

// Select multiple nodes programmatically
Tree1.Selected.Clear;
Node1.Selected := True;
Node2.Selected := True;
Node3.Selected := True;

Complete Example

Here’s a complete example showing selection management:

type
  TSelectingNodesForm = class(TForm)
    Tree1: TTree;
    Button1: TButton;
    ButtonDelete: TButton;
    LabelStatus: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Tree1SelectShape(Sender: TTreeNodeShape);
    procedure Tree1UnSelectShape(Sender: TTreeNodeShape);
    procedure ButtonDeleteClick(Sender: TObject);
  end;

procedure TSelectingNodesForm.FormCreate(Sender: TObject);
begin
  // Create sample nodes
  Tree1.Add('Node 1');
  Tree1.Add('Node 2');
  Tree1.Add('Node 3');
  
  // Enable multiple selection
  Tree1.MultiSelect := True;
  
  // Initially disable delete button
  ButtonDelete.Enabled := False;
end;

procedure TSelectingNodesForm.Button1Click(Sender: TObject);
begin
  // Select all nodes
  Tree1.Selected.SelectAll;
end;

procedure TSelectingNodesForm.Tree1SelectShape(Sender: TTreeNodeShape);
begin
  // Update status label
  LabelStatus.Caption := 'Selected: ' + IntToStr(Tree1.Selected.Count) + ' node(s)';
  
  // Enable delete button
  ButtonDelete.Enabled := True;
end;

procedure TSelectingNodesForm.Tree1UnSelectShape(Sender: TTreeNodeShape);
begin
  // Update status label
  if Tree1.Selected.Count = 0 then
  begin
    LabelStatus.Caption := 'No nodes selected';
    ButtonDelete.Enabled := False;
  end
  else
    LabelStatus.Caption := 'Selected: ' + IntToStr(Tree1.Selected.Count) + ' node(s)';
end;

procedure TSelectingNodesForm.ButtonDeleteClick(Sender: TObject);
var
  i: Integer;
begin
  // Delete all selected nodes (iterate backwards to avoid index issues)
  for i := Tree1.Selected.Count - 1 downto 0 do
    Tree1.Selected[i].Free;
end;

Selection with Keyboard

Users can select nodes using keyboard navigation:

• Arrow keys: Navigate between nodes
• Ctrl+Click: Add/remove nodes from selection (with MultiSelect enabled)
• Shift+Click: Select range of nodes (with MultiSelect enabled)

Key Points

• Use Selected property to programmatically select/deselect nodes
• Use Tree1.Selected collection to access all selected nodes
• Use OnSelectShape and OnUnSelectShape events to respond to selection changes
• Enable MultiSelect property for multiple node selection
• Always check Assigned(Tree1.Selected.First) before accessing selected nodes
• Use Tree1.Selected.Clear before making new selections to avoid accumulation
• Iterate backwards when deleting multiple selected nodes to avoid index issues