只允许建立一次子窗体的MDI程序

核心提示：PRocedure OpenChildForm(FormClass: TFormClass; var Fm; AOwner:TComponent);var I: Integer; Child: TForm;begin for I := 0 to Screen.FormCount - 1 do if Screen

PRocedure OpenChildForm(FormClass: TFormClass; var Fm; AOwner:TComponent);
var
  I: Integer;
  Child: TForm;
begin
  for I := 0 to Screen.FormCount - 1 do
　  if Screen.Forms[I].ClassType = FormClass then
　  begin
　　  Child := Screen.Forms[I];
　　  if Child.WindowState = wsMinimized then
　　　  ShowWindow(Child.Handle, SW_SHOWNORMAL)
　　  else
　　　  ShowWindow(Child.handle,SW_SHOWNA);
　　  if (not Child.Visible) then Child.Visible := True;
　　　  Child.BringToFront;
　　　  Child.Setfocus;
　　　  TForm(Fm) := Child;
　　　  Exit;
　  end;
  Child := TForm(FormClass.NewInstance);
  TForm(Fm) := Child;
  Child.Create(AOwner);
end;