动态创建子窗体时老提示No MDI Forms are currently active,

Question

原来程序的主窗体是登录窗口，后来又改为MDI窗口为主窗口，
但是运行到 Application.CreateForm(TCompanyInfoForm,CompanyInfoForm)
时就出现上面的错误，不知道是怎么回事情。代码如下：
procedure TMainForm.CompanyInfoExecute(Sender: TObject);
begin
  screen.Cursor:=crhourglass;
try
    if CompanyInfoForm=nil then
//       CompanyInfoForm:=TCompanyInfoForm.Create(MainForm);
        Application.CreateForm(TCompanyInfoForm,CompanyInfoForm);
    CompanyInfoForm.Show;
finally
  screen.Cursor:=crdefault;
end;
end;

Answer 1

设置一下主窗口的FormStyle 为MDIMain看行不行

Answer 2

qiujsh(qiujsh) :我已经设为fsMDIForm了，但还是老样子。