请问在父子窗口中输入法的切换怎么解决 请高手帮忙了

Question

网上的有关程序如：Procedure TXianzc_FM.ChangeYouFormAllControlIme(YFormName:TWinControl);
var
  i:integer;
  ChildControl:TControl;
  Reg:TRegistry;
  YouFormOrOTher:TWinControl;
begin
  YouFormOrOTher:=YFormName;
  reg:=TRegistry.Create;
  //¶Áȡע²á±í±£´æµÄÓû§Ñ¡ÔñµÄÊäÈë·¨,Óõ¥ÔªÈ«¾Ö±äÁ¿ StrImeName ±£´æ
  reg.RootKey:=HKEY_LOCAL_MACHINE;
  try
    if Reg.OpenKey('\Software\IMeCustom',false)=true then
     StrImeName:=reg.ReadString('CustomIMeName');
  finally
    reg.CloseKey;
    reg.Free;
   end;
   try
   for i:=0 to YouFormOrOTher.ControlCount-1 do
  begin
    ChildControl:=YouFormOrOTher.Controls[i];
    JugeClassType(ChildControl);
    if ChildControl is TWinControl then
      ChangeYouFormAllControlIme(ChildControl as TWinControl);
  end;调用这个过程  ChangeYouFormAllControlIme(YFormName:TWinControl);
 为什么YFormName总 NIL 呀