确定delphi的ActivePage中的哪种形式

Question

我有一个带有pagecontrol的主形式(frmmain(。PageControl在启动时以几种形式填充，让我们说Form1，Form2和Form3

procedure TForm1.FormCreate(Sender: TObject);
begin
   ManualDock(frmMain.PageControl1);
   show;
end;
procedure TForm2.FormCreate(Sender: TObject);
begin
   ManualDock(frmMain.PageControl1);
   show;
end;
procedure TForm3.FormCreate(Sender: TObject);
begin
   ManualDock(frmMain.PageControl1);
   show;
end;

效果很好。然后，当我更改ActivePage时，我希望在与ActivePage相对应的单上调用on Activate方法，因此我尝试了;

procedure TfrmMain.PageControl1Change(Sender: TObject);
begin
  with pagecontrol1 do
  begin
     lbHeading.Caption := activepage.Caption;
     with tform(activepage) do        // <= This does 
     if assigned(onactivate) then     // <= not
     onactivate(self);                // <= work
  end;
end;

ActivePage是类型TTABSHEET

Answer 1

我找到了一个解决方案：

with pagecontrol1 do
begin
  with tform(activepage.controls[0]) do
  if assigned(onactivate) then
  onactivate(self);
end;