Creating MDI Tabbed Interface (Sample)

// Creating MDI = Multiple Document Interface with Tabbed Interface (with Sample Codes)

 // Unit 1 Form

// Unit 2 Form

// Running Application

// Sample Code

unit Unit1;

interface

uses
     // ... please put your own...
type
  TMainForm = class(TForm)
    mdiChildrenTabs: TTabSet;
    ToolBar1: TToolBar;
    ToolButton1: TToolButton;
    procedure mdiChildrenTabsChange(Sender: TObject; NewTab: Integer;
      var AllowChange: Boolean);
    procedure ToolButton1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    Procedure MDIChildCreated(const childHandle : THandle);
    Procedure MDIChildDestroyed(const childHandle : THandle);
  end;

var
  MainForm: TMainForm;

implementation

{$R *.dfm}

uses Unit2;
// ****************************************************************************** //
procedure TMainForm.mdiChildrenTabsChange(Sender: TObject; NewTab: Integer;
  var AllowChange: Boolean);  
// ****************************************************************************** //
var
  cHandle: Integer;
  k: Integer;
begin
  cHandle := Integer(mdiChildrenTabs.Tabs.Objects[NewTab]);

  if mdiChildrenTabs.Tag = -1 then Exit;

  for k := 0 to MDIChildCount - 1 do
  begin
    if MDIChildren[k].Handle = cHandle then
    begin
      MDIChildren[k].Show;
      Break;
    end;
  end;
end;

// ****************************************************************************** //
procedure TMainForm.ToolButton1Click(Sender: TObject);
// ****************************************************************************** //
var FormChild : TBaseChildForm;
begin
  FormChild:=TBaseChildForm.Create(nil);
  FormChild.Show;
end;

// ****************************************************************************** //
procedure TMainForm.MDIChildCreated(const childHandle: THandle);
// ****************************************************************************** //
begin
  mdiChildrenTabs.Tabs.AddObject(TForm(FindControl(childHandle)).Caption, TObject(childHandle));
  mdiChildrenTabs.TabIndex := -1 + mdiChildrenTabs.Tabs.Count;
end;

// ****************************************************************************** //
procedure TMainForm.MDIChildDestroyed(const childHandle: THandle);
// ****************************************************************************** //
var
  idx: Integer;
begin
  idx := mdiChildrenTabs.Tabs.IndexOfObject(TObject(childHandle));
  mdiChildrenTabs.Tabs.Delete(idx);
end;

end. 

// ********************************** Unit 2 *********************************** //

unit Unit2;

interface

uses
     // ... please put your own...

type
  TBaseChildForm = class(TForm)
    Button1: TButton;
    Panel1: TPanel;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
    procedure WMMDIACTIVATE(var msg : TWMMDIACTIVATE) ; message WM_MDIACTIVATE;
  public
    { Public declarations }
  end;

var
  BaseChildForm: TBaseChildForm;

implementation

{$R *.dfm}

uses Unit1;

{ TBaseChildForm }

// ****************************************************************************** //
procedure TBaseChildForm.Button1Click(Sender: TObject);
// ****************************************************************************** //
begin
  panel1.Caption:='Hello World';
end;

// ****************************************************************************** //
procedure TBaseChildForm.FormCreate(Sender: TObject);
// ****************************************************************************** //
begin
  MainForm.MDIChildCreated(self.Handle)
end;

// ****************************************************************************** //
procedure TBaseChildForm.FormDestroy(Sender: TObject);
// ****************************************************************************** //
begin
  MainForm.MDIChildDestroyed(self.Handle);
end;

// ****************************************************************************** //
procedure TBaseChildForm.FormClose(Sender: TObject; var Action: TCloseAction);
// ****************************************************************************** //
begin
  action:=caFree;
end;

// ****************************************************************************** //
procedure TBaseChildForm.WMMDIACTIVATE(var msg: TWMMDIACTIVATE);
// ****************************************************************************** //
var
  active: TWinControl;
  idx: Integer;
begin
  active := FindControl(msg.ActiveWnd) ;

  if Assigned(active) then
  begin
    idx := MainForm.mdiChildrenTabs.Tabs.IndexOfObject(TObject(msg.ActiveWnd));
    MainForm.mdiChildrenTabs.Tag := -1;
    MainForm.mdiChildrenTabs.TabIndex := idx;
    MainForm.mdiChildrenTabs.Tag := 0;
  end;
end;

end.