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Overview

TeeGrid supports master-detail relationships where clicking an expand icon reveals a nested sub-grid. This works with databases, arrays, and any data source.

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Basic Master-Detail

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Setting Up the Master Grid

uses
  FMXTee.Control, FMXTee.Grid, Tee.GridData.DB, Tee.Grid.RowGroup;

procedure TMasterDetail.FormCreate(Sender: TObject);
begin
  // Open the master dataset (Customers)
  SampleData.CustomersTable.Open;
  
  // Bind to grid
  TeeGrid1.DataSource := SampleData.CustomersTable;
  
  // Enable the expander
  CBEnabledChange(Self);
end;

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Creating the Expander

From the FireMonkey Master-Detail demo: 
procedure TMasterDetail.EnableDisableSubGrid(const AGroup: TRowGroup;
  const AEvent: TExpanderGetDataEvent);
var
  Expander: TExpanderRender;
begin
  if CBEnabled.IsChecked then
  begin
    // Create the expander control
    Expander := AGroup.NewExpander;
    
    // Set the event that provides detail data
    Expander.OnGetData := AEvent;
    
    // Always show expand icon (we don't know in advance if detail exists)
    Expander.AlwaysExpand := True;
    
    // Add expander to first column
    if AGroup.Columns.Count > 0 then
      AGroup.Columns[0].Render := Expander;
  end
  else
  begin
    // Remove all detail grids
    AGroup.Rows.Children.Clear;
    
    // Remove expander from first column
    if AGroup.Columns.Count > 0 then
      AGroup.Columns[0].Render := nil;
  end;
end;

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Providing Detail Data

// Called when a master row is expanded
procedure TMasterDetail.GetOrders(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  // Return a new dataset for the detail grid
  AData := TVirtualDBData.From(SampleData.OrdersOfCustomer(ARow + 1));
  
  // Mark data as owned by the grid (will be auto-freed)
  TVirtualDBData(AData).OwnsData := True;
end;

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Multi-Level Master-Detail

You can nest multiple levels (Customer -> Orders -> Order Details): 
procedure TMasterDetail.FormCreate(Sender: TObject);
begin
  SampleData.CustomersTable.Open;
  TeeGrid1.DataSource := SampleData.CustomersTable;
  
  // Level 1: Customer -> Orders
  EnableDisableSubGrid(TeeGrid1.Grid.Current, GetOrders);
  
  // Handle when a new detail grid is created
  TeeGrid1.Grid.Current.OnNewDetail := DetailNewGroup;
end;

// Called when first detail level is created (Orders)
procedure TMasterDetail.DetailNewGroup(const Sender, NewGroup: TRowGroup);
var
  tmpTot: TColumnTotals;
begin
  // Level 2: Orders -> Order Details
  EnableDisableSubGrid(NewGroup, GetOrderItems);
  
  // Handle when sub-detail grid is created
  NewGroup.OnNewDetail := SubDetailNewGroup;
  
  // Add totals to the detail grid footer
  tmpTot := TColumnTotals.Create(NewGroup.Footer);
  tmpTot.Calculation.Add(NewGroup.Columns[0], TColumnCalculation.Count);
  tmpTot.Calculation.Add('EmployeeID', TColumnCalculation.Sum);
  
  // Add totals header
  TTotalsHeader.CreateTotals(NewGroup.Footer, tmpTot);
  
  // Customize appearance
  NewGroup.Rows.Back.Brush.Color := TAlphaColors.Bisque;
  NewGroup.Rows.Back.Brush.Visible := True;
  NewGroup.Cells.Format.Font.Color := TAlphaColors.Darkblue;
end;

// Level 2 detail data provider
procedure TMasterDetail.GetOrderItems(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  AData := TVirtualDBData.From(SampleData.OrderDetailsOfOrder(ARow + 1));
  TVirtualDBData(AData).OwnsData := True;
end;

​
Complete Example

From Master_Detail_FireDAC.pas: 
unit Master_Detail_FireDAC;

interface

uses
  FMX.Forms, FMX.StdCtrls, FMX.Layouts, Data.DB,
  FMXTee.Control, FMXTee.Grid,
  Tee.Grid.RowGroup, Tee.Renders;

type
  TMasterDetail = class(TForm)
    TeeGrid1: TTeeGrid;
    CBEnabled: TCheckBox;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure CBEnabledChange(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    procedure DetailNewGroup(const Sender, NewGroup: TRowGroup);
    procedure SubDetailNewGroup(const Sender, NewGroup: TRowGroup);
    procedure EnableDisableSubGrid(const AGroup: TRowGroup;
      const AEvent: TExpanderGetDataEvent);
    procedure GetOrders(const Sender: TExpanderRender;
      const ARow: Integer; out AData: TObject);
    procedure GetOrderItems(const Sender: TExpanderRender;
      const ARow: Integer; out AData: TObject);
  end;

var
  MasterDetail: TMasterDetail;
  Open: Boolean;

implementation

uses
  Tee.Grid.Totals, Tee.GridData.DB, Tee.Grid.Columns,
  System.UIConsts, Customer_Orders;

procedure TMasterDetail.FormCreate(Sender: TObject);
begin
  // Open master table
  SampleData.CustomersTable.Open;
  TeeGrid1.DataSource := SampleData.CustomersTable;
  
  Open := False;
  
  // Initialize expander
  CBEnabledChange(Self);
  
  // Set up detail creation event
  TeeGrid1.Grid.Current.OnNewDetail := DetailNewGroup;
end;

procedure TMasterDetail.Button1Click(Sender: TObject);
begin
  // Toggle expand/collapse all
  if Open then
  begin
    TeeGrid1.Grid.Current.ShowHideAllDetail(0, False);
    Open := False;
  end
  else
  begin
    TeeGrid1.Grid.Current.ShowHideAllDetail(0, True);
    Open := True;
  end;
end;

procedure TMasterDetail.EnableDisableSubGrid(const AGroup: TRowGroup;
  const AEvent: TExpanderGetDataEvent);
var
  Expander: TExpanderRender;
begin
  if CBEnabled.IsChecked then
  begin
    // Create expander
    Expander := AGroup.NewExpander;
    Expander.OnGetData := AEvent;
    Expander.AlwaysExpand := True;
    
    if AGroup.Columns.Count > 0 then
      AGroup.Columns[0].Render := Expander;
  end
  else
  begin
    // Remove detail grids
    AGroup.Rows.Children.Clear;
    
    if AGroup.Columns.Count > 0 then
      AGroup.Columns[0].Render := nil;
  end;
end;

procedure TMasterDetail.CBEnabledChange(Sender: TObject);
begin
  EnableDisableSubGrid(TeeGrid1.Grid.Current, GetOrders);
end;

procedure TMasterDetail.DetailNewGroup(const Sender, NewGroup: TRowGroup);
var
  tmpTot: TColumnTotals;
begin
  // Set up second level expander
  EnableDisableSubGrid(NewGroup, GetOrderItems);
  NewGroup.OnNewDetail := SubDetailNewGroup;
  
  // Add totals
  tmpTot := TColumnTotals.Create(NewGroup.Footer);
  tmpTot.Calculation.Add(NewGroup.Columns[0], TColumnCalculation.Count);
  tmpTot.Calculation.Add('EmployeeID', TColumnCalculation.Sum);
  TTotalsHeader.CreateTotals(NewGroup.Footer, tmpTot);
  
  // Styling
  NewGroup.Rows.Back.Brush.Color := TAlphaColors.Bisque;
  NewGroup.Rows.Back.Brush.Visible := True;
  NewGroup.Cells.Format.Font.Color := TAlphaColors.Darkblue;
end;

procedure TMasterDetail.SubDetailNewGroup(const Sender, NewGroup: TRowGroup);
begin
  // Style the third level
  NewGroup.Rows.Back.Brush.Color := TAlphaColors.Lavender;
  NewGroup.Rows.Back.Brush.Visible := True;
  NewGroup.Cells.Format.Font.Color := TAlphaColors.Blueviolet;
end;

procedure TMasterDetail.GetOrders(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  // Return orders for customer
  AData := TVirtualDBData.From(SampleData.OrdersOfCustomer(ARow + 1));
  TVirtualDBData(AData).OwnsData := True;
end;

procedure TMasterDetail.GetOrderItems(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  // Return order items for order
  AData := TVirtualDBData.From(SampleData.OrderDetailsOfOrder(ARow + 1));
  TVirtualDBData(AData).OwnsData := True;
end;

end.

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Key Concepts

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Expander Render

The TExpanderRender displays the expand/collapse icon: 
Expander := AGroup.NewExpander;
Expander.OnGetData := GetDetailData;  // Called when expanded
Expander.AlwaysExpand := True;        // Always show icon

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OnGetData Event

procedure GetDetailData(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  // Create and return data for the detail grid
  AData := TVirtualDBData.From(MyDetailDataset);
  
  // Grid will free the data when row is collapsed
  TVirtualDBData(AData).OwnsData := True;
end;

​
OnNewDetail Event

Called when a new detail grid is created: 
procedure DetailCreated(const Sender, NewGroup: TRowGroup);
begin
  // Customize the new detail grid
  NewGroup.Rows.Back.Brush.Color := TAlphaColors.LightBlue;
  
  // Add totals, custom bands, etc.
  // ...
end;

​
Adding Totals to Detail Grids

uses
  Tee.Grid.Totals;

procedure AddTotalsToDetail(const AGroup: TRowGroup);
var
  tmpTot: TColumnTotals;
begin
  // Create totals band
  tmpTot := TColumnTotals.Create(AGroup.Footer);
  
  // Add calculations
  tmpTot.Calculation.Add(AGroup.Columns[0], TColumnCalculation.Count);
  tmpTot.Calculation.Add('Amount', TColumnCalculation.Sum);
  tmpTot.Calculation.Add('Price', TColumnCalculation.Average);
  
  // Add header
  TTotalsHeader.CreateTotals(AGroup.Footer, tmpTot);
  
  // Style the totals
  tmpTot.Format.Font.Style := [fsBold];
end;

​
Expand/Collapse All

// Expand all detail rows at level 0
TeeGrid1.Grid.Current.ShowHideAllDetail(0, True);

// Collapse all detail rows
TeeGrid1.Grid.Current.ShowHideAllDetail(0, False);

​
Styling Detail Grids

procedure StyleDetailGrid(const AGroup: TRowGroup);
begin
  // Background color
  AGroup.Rows.Back.Brush.Color := TAlphaColors.Bisque;
  AGroup.Rows.Back.Brush.Visible := True;
  
  // Font color
  AGroup.Cells.Format.Font.Color := TAlphaColors.Darkblue;
  
  // Border
  AGroup.Rows.RowLines.Color := TAlphaColors.Gray;
  AGroup.Rows.RowLines.Show;
end;

​
Features

  • Multiple Levels: Nest as many levels as needed
  • Lazy Loading: Detail data loaded only when expanded
  • Automatic Cleanup: Detail grids freed when collapsed
  • Custom Styling: Each level can have different appearance
  • Totals Support: Add summary calculations to detail grids
  • Expand/Collapse All: Programmatic control

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Common Patterns

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Database Master-Detail

// Master: Customers
TeeGrid1.DataSource := CustomersTable;

// Detail: Orders filtered by CustomerID
procedure GetOrders(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  OrdersQuery.Close;
  OrdersQuery.ParamByName('CustomerID').AsInteger := ARow + 1;
  OrdersQuery.Open;
  
  AData := TVirtualDBData.From(OrdersQuery);
  TVirtualDBData(AData).OwnsData := True;
end;

​
Array Master-Detail

type
  TOrderItem = record
    Product: String;
    Quantity: Integer;
  end;
  
  TOrder = record
    OrderID: Integer;
    Items: TArray<TOrderItem>;
  end;

procedure GetOrderItems(const Sender: TExpanderRender;
  const ARow: Integer; out AData: TObject);
begin
  // Return array data for detail
  AData := TVirtualArrayData<TOrderItem>.Create(Orders[ARow].Items);
end;

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Best Practices

  1. Set OwnsData := True so grid automatically frees detail data
  2. Use OnNewDetail to customize newly created detail grids
  3. Enable AlwaysExpand when you can’t determine if detail exists
  4. Style each level differently for visual hierarchy
  5. Add totals to detail grids for better insight

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Next Steps

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