Is there a data-aware tab control available?

Question

Data-aware controls can be linked to datasets to display data contained in fields in the current row, or in some cases, data from one or more columns along multiple rows. And the TTabControl lets you apply the same set of controls to different sets of data values in an easy-to-understand way.

Seems to me that they would go well together. TTabControl would make a good data-aware control (link it to an identity column in the dataset and it could be a much more intuitive navigator than TDBNavigator), but there isn't one in the VCL.

Has anyone out there created a data-aware tab control? The only one I've found is DBTABCONTROL98 by Jean-Luc Mattei, which dates back to 1998 (Delphi 3 era) and, even after modifying it to get it to compile under XE, does not actually work. Are there any others that work as expected? (ie. adding/deleting tabs when new records are added/removed from the dataset, and switching the dataset's active row when the user changes tabs and vice versa.)

And yes, I'm aware that that could get a bit unwieldy if there are a lot of rows in the dataset. I'm looking for something to build a UI for a use case where the number of rows is in single- or very low double digits.

Answer 1

I wrote a TDBTabControl for you. If you do not set the DataField property, then the captions of tabs will be the record index. The starred tab indicates a new record, which visibility can be toggled with the ShowInsertTab property.

I inherited from TCustomTabControl because the properties Tabs, TabIndex and MultiSelect may not be published for this component.

unit DBTabControl;

interface

uses
  Classes, Windows, SysUtils, Messages, Controls, ComCtrls, DB, DBCtrls;

type
  TCustomDBTabControl = class(TCustomTabControl)
  private
    FDataLink: TFieldDataLink;
    FPrevTabIndex: Integer;
    FShowInsertTab: Boolean;
    procedure ActiveChanged(Sender: TObject);
    procedure DataChanged(Sender: TObject);
    function GetDataField: String;
    function GetDataSource: TDataSource;
    function GetField: TField;
    procedure RebuildTabs;
    procedure SetDataField(const Value: String);
    procedure SetDataSource(Value: TDataSource);
    procedure SetShowInsertTab(Value: Boolean);
    procedure CMExit(var Message: TCMExit); message CM_EXIT;
    procedure CMGetDataLink(var Message: TMessage); message CM_GETDATALINK;
  protected
    function CanChange: Boolean; override;
    procedure Change; override;
    procedure KeyDown(var Key: Word; Shift: TShiftState); override;
    procedure Notification(AComponent: TComponent; Operation: TOperation);
      override;
    procedure Loaded; override;
    property DataField: String read GetDataField write SetDataField;
    property DataSource: TDataSource read GetDataSource write SetDataSource;
    property Field: TField read GetField;
    property ShowInsertTab: Boolean read FShowInsertTab write SetShowInsertTab
      default False;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    function ExecuteAction(Action: TBasicAction): Boolean; override;
    function UpdateAction(Action: TBasicAction): Boolean; override;
  end;

  TDBTabControl = class(TCustomDBTabControl)
  public
    property DisplayRect;
    property Field;
  published
    property Align;
    property Anchors;
    property BiDiMode;
    property Constraints;
    property DockSite;
    property DataField;
    property DataSource;
    property DragCursor;
    property DragKind;
    property DragMode;
    property Enabled;
    property Font;
    property HotTrack;
    property Images;
    property MultiLine;
    property OwnerDraw;
    property ParentBiDiMode;
    property ParentFont;
    property ParentShowHint;
    property PopupMenu;
    property RaggedRight;
    property ScrollOpposite;
    property ShowHint;
    property ShowInsertTab;
    property Style;
    property TabHeight;
    property TabOrder;
    property TabPosition;
    property TabStop;
    property TabWidth;
    property Visible;
    property OnChange;
    property OnChanging;
    property OnContextPopup;
    property OnDockDrop;
    property OnDockOver;
    property OnDragDrop;
    property OnDragOver;
    property OnDrawTab;
    property OnEndDock;
    property OnEndDrag;
    property OnEnter;
    property OnExit;
    property OnGetImageIndex;
    property OnGetSiteInfo;
    property OnMouseDown;
    property OnMouseMove;
    property OnMouseUp;
    property OnResize;
    property OnStartDock;
    property OnStartDrag;
    property OnUnDock;
  end;

implementation

{ TCustomDBTabControl }

procedure TCustomDBTabControl.ActiveChanged(Sender: TObject);
begin
  RebuildTabs;
end;

function TCustomDBTabControl.CanChange: Boolean;
begin
  FPrevTabIndex := TabIndex;
  Result := (inherited CanChange) and (DataSource <> nil) and
    (DataSource.State in [dsBrowse, dsEdit, dsInsert]);
end;

procedure TCustomDBTabControl.Change;
var
  NewTabIndex: Integer;
begin
  try
    if FDataLink.Active and (DataSource <> nil) then
    begin
      if FShowInsertTab and (TabIndex = Tabs.Count - 1) then
        DataSource.DataSet.Append
      else if DataSource.State = dsInsert then
      begin
        NewTabIndex := TabIndex;
        DataSource.DataSet.CheckBrowseMode;
        DataSource.DataSet.MoveBy(NewTabIndex - TabIndex);
      end
      else
        DataSource.DataSet.MoveBy(TabIndex - FPrevTabIndex);
    end;
    inherited Change;
  except
    TabIndex := FPrevTabIndex;
    raise;
  end;
end;

procedure TCustomDBTabControl.CMExit(var Message: TCMExit);
begin
  try
    FDataLink.UpdateRecord;
  except
    SetFocus;
    raise;
  end;
  inherited;
end;

procedure TCustomDBTabControl.CMGetDataLink(var Message: TMessage);
begin
  Message.Result := Integer(FDataLink);
end;

constructor TCustomDBTabControl.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FDataLink := TFieldDataLink.Create;
  FDataLink.Control := Self;
  FDataLink.OnActiveChange := ActiveChanged;
  FDataLink.OnDataChange := DataChanged;
end;

procedure TCustomDBTabControl.DataChanged(Sender: TObject);
const
  StarCount: array[Boolean] of Integer = (0, 1);
var
  NewTabIndex: Integer;
begin
  if FDataLink.Active and (DataSource <> nil) then
    with DataSource do
    begin
      if DataSet.RecordCount <> Tabs.Count - StarCount[FShowInsertTab] then
        RebuildTabs
      else if (State = dsInsert) and FShowInsertTab then
        TabIndex := Tabs.Count - 1
      else if Tabs.Count > 0 then
      begin
        NewTabIndex := Tabs.IndexOfObject(TObject(DataSet.RecNo));
        if (TabIndex = NewTabIndex) and (State <> dsInsert) and
            (Field <> nil) and (Field.AsString <> Tabs[TabIndex]) then
          Tabs[TabIndex] := Field.AsString;
        TabIndex := NewTabIndex;
      end;
    end;
end;

destructor TCustomDBTabControl.Destroy;
begin
  FDataLink.Free;
  FDataLink := nil;
  inherited Destroy;
end;

function TCustomDBTabControl.ExecuteAction(Action: TBasicAction): Boolean;
begin
  Result := inherited ExecuteAction(Action) or FDataLink.ExecuteAction(Action);
end;

function TCustomDBTabControl.GetDataField: String;
begin
  Result := FDataLink.FieldName;
end;

function TCustomDBTabControl.GetDataSource: TDataSource;
begin
  Result := FDataLink.DataSource;
end;

function TCustomDBTabControl.GetField: TField;
begin
  Result := FDataLink.Field;
end;

procedure TCustomDBTabControl.KeyDown(var Key: Word; Shift: TShiftState);
begin
  if (DataSource <> nil) and (DataSource.State = dsInsert) and
    (Key = VK_ESCAPE) then
  begin
    DataSource.DataSet.Cancel;
    Change;
  end;
  inherited keyDown(Key, Shift);
end;

procedure TCustomDBTabControl.Loaded;
begin
  inherited Loaded;
  if (csDesigning in ComponentState) then
    RebuildTabs;
end;

procedure TCustomDBTabControl.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited Notification(AComponent, Operation);
  if (Operation = opRemove) and (FDataLink <> nil) and
      (AComponent = DataSource) then
    DataSource := nil;
end;

procedure TCustomDBTabControl.RebuildTabs;
var
  Bookmark: TBookmark;
begin
  if (DataSource <> nil) and (DataSource.State = dsBrowse) then
    with DataSource do
    begin
      if HandleAllocated then
        LockWindowUpdate(Handle);
      Tabs.BeginUpdate;
      DataSet.DisableControls;
      BookMark := DataSet.GetBookmark;
      try
        Tabs.Clear;
        DataSet.First;
        while not DataSet.Eof do
        begin
          if Field = nil then
            Tabs.AddObject(IntToStr(Tabs.Count + 1), TObject(DataSet.RecNo))
          else
            Tabs.AddObject(Field.AsString, TObject(DataSet.RecNo));
          DataSet.Next;
        end;
        if FShowInsertTab then
          Tabs.AddObject('*', TObject(-1));
      finally
        DataSet.GotoBookmark(Bookmark);
        DataSet.FreeBookmark(Bookmark);
        DataSet.EnableControls;
        Tabs.EndUpdate;
        if HandleAllocated then
          LockWindowUpdate(0);
      end;
    end
  else
    Tabs.Clear;
end;

procedure TCustomDBTabControl.SetDataField(const Value: String);
begin
  FDataLink.FieldName := Value;
  RebuildTabs;
end;

procedure TCustomDBTabControl.SetDataSource(Value: TDataSource);
begin
  FDataLink.DataSource := Value;
  if DataSource <> nil then
    DataSource.FreeNotification(Self);
  if not (csLoading in ComponentState) then
    RebuildTabs;
end;

procedure TCustomDBTabControl.SetShowInsertTab(Value: Boolean);
begin
  if FShowInsertTab <> Value then
  begin
    FShowInsertTab := Value;
    RebuildTabs;
  end;
end;

function TCustomDBTabControl.UpdateAction(Action: TBasicAction): Boolean;
begin
  Result := inherited UpdateAction(Action) or FDataLink.UpdateAction(Action);
end;

end.

unit DBTabControlReg;

interface

uses
  Classes, DBTabControl;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Samples', [TDBTabControl]);
end;

end.

package DBTabControl70;

{$R *.res}
{$ALIGN 8}
{$ASSERTIONS ON}
{$BOOLEVAL OFF}
{$DEBUGINFO ON}
{$EXTENDEDSYNTAX ON}
{$IMPORTEDDATA ON}
{$IOCHECKS ON}
{$LOCALSYMBOLS ON}
{$LONGSTRINGS ON}
{$OPENSTRINGS ON}
{$OPTIMIZATION OFF}
{$OVERFLOWCHECKS ON}
{$RANGECHECKS ON}
{$REFERENCEINFO ON}
{$SAFEDIVIDE OFF}
{$STACKFRAMES ON}
{$TYPEDADDRESS OFF}
{$VARSTRINGCHECKS ON}
{$WRITEABLECONST OFF}
{$MINENUMSIZE 1}
{$IMAGEBASE $400000}
{$DESCRIPTION '#DBTabControl'}
{$IMPLICITBUILD OFF}

requires
  rtl,
  vcl,
  dbrtl,
  vcldb;

contains
  DBTabControl in 'DBTabControl.pas',
  DBTabControlReg in 'DBTabControlReg.pas';

end.