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Overview

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

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Selecting Nodes Programmatically

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Select a Single Node

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

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

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Select All Nodes

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

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Clear Selection

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

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Working with Selected Nodes

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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;

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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;

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Selection Events

TeeTree provides events to respond to selection changes:

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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;

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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;

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Selection Properties

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Check if a Node is Selected

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

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Get Selection Count

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

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Check if Any Node is Selected

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

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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;

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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;

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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)

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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

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