delphiMDI程序的设计

Question

本人在自学delphi，有一段代码看不懂，求教各位大神解释，越详细越好
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;

Answer 1

 procedure OpenChildForm(FormClass: TFormClass; var Fm; AOwner:TComponent); 打开子窗口（窗口类型，父窗口）
var
i: integer;
Child:TForm;
begin
for i := 0 to Screen.FormCount -1 do
if Screen.Forms[i].ClassType=FormClass then //遍历屏幕上所有的窗口，寻找类型和参数传来的一样的
begin
Child:=Screen.Forms[i];
if Child.WindowState=wsMinimized then //如果窗口最小化，那么显示它
ShowWindow(Child.handle,SW_SHOWNORMAL)
else
ShowWindow(Child.handle,SW_SHOWNA); //否则隐藏它
if (not Child.Visible) then Child.Visible:=True;
Child.BringToFront; //把窗口放入前台
Child.Setfocus; //设置输入焦点
TForm(Fm):=Child;
exit; //退出
end;
Child:=TForm(FormClass.NewInstance); //如果没找到，那么就走不到退出的地方，进入这里
TForm(fm):=Child; //创建新窗口
Child.Create(AOwner);
end;