Question

delphi 如何在MDI窗体中新建子窗体，且只让子窗体显示一次？

Answer 1

定义一个窗口实例公用变量unit
Unit1;interfaceuses
Windows,
Messages,
SysUtils,
Variants,
Classes,
Graphics,
Controls,
Forms,
Dialogs;type
TForm1
=
class(TForm)
private
public
end;var
Form1:
TForm1;
fm2:
TForm2;//在这里定义implementation{$R
*.dfm}end.然后让其它的窗口不自动创建。这时在菜单里这样写if
fm2<>nil
then
fm2:=Tform2.create(self);fm2.show;就可以了

Answer 2

if
Assigned(form1)
then
//判断form1是否为空,是空就创建。begin
form1:=TForm1.Create(self);
form1.Show;endelse
form1.show;在关闭窗体时要释放action=nil;