问题描述
- delphi 中MDI程序设计 10C
-
本人在编写MDI程序建立子窗体时，出现如图所示的错误，求教大神！具体内容：建立三个窗体mianformjchildform1childform2在mainform上放两个按钮，buttto1button2分别点击这两个按钮，能够在mainform中打开两个子窗体。部分代码如下：
mainform中的代码:
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.handleSW_SHOWNORMAL)
else
ShowWindow(Child.handleSW_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;procedure TMainForm.Button1Click(Sender: TObject);
begin
OpenChildForm(TChildForm1ChildForm1 Self);
end;procedure TMainForm.Button2Click(Sender: TObject);
begin
OpenChildForm(TChildForm2ChildForm2 Self);
end;childform1childform2 中代码相同： Action:=caFree;错误提示： project project1.exe rasied exception class EInvalidOperation with message 'cannot create form.No MDI forms are currently active.
解决方案
你使用raise 异常捕获啊，两个 ChildForm ，没有实例化，是随机值指针吧，先创建在传进去试试
解决方案二：
一、子窗口要动态创建
二、调用子窗口的代码
if not Assigned(SetSaleFrm) then
begin
SetSaleFrm:=TSetSaleFrm.Create(Self);
SetSaleFrm.WindowState:=MID_WindowState;
end
else SetSaleFrm.BringToFront;