有关窗体的不解问题 ( 积分: 20 )

P

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• 2005-07-25

• #1

下面用TFormClass的方法为什么不行,如何才能使其工作正常
implementation
uses Unit2;
{$R *.dfm}
procedure TForm1.OpenForm(aFormClass:TFormClass;Obj:TForm);
begin
Obj:=aFormClass.Create(Application);
//Application.CreateForm(aFormClass,Obj);
Obj.Show;
end;
procedure TForm1.BitBtn1Click(Sender: TObject);

begin
OpenForm(TForm2,Form2);
Form2.Caption:='test'
//不行
end;

procedure TForm1.BitBtn2Click(Sender: TObject);
begin
Form2:=TForm2.Create(Application);
Form2.Show;
Form2.Caption:='test'
//可以
end;

end.

 

P

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• 2005-07-25

• #2

下面用TFormClass的方法为什么不行,如何才能使其工作正常
implementation
uses Unit2;
{$R *.dfm}
procedure TForm1.OpenForm(aFormClass:TFormClass;Obj:TForm);
begin
Obj:=aFormClass.Create(Application);
//Application.CreateForm(aFormClass,Obj);
Obj.Show;
end;
procedure TForm1.BitBtn1Click(Sender: TObject);

begin
OpenForm(TForm2,Form2);
Form2.Caption:='test'
//不行
end;

procedure TForm1.BitBtn2Click(Sender: TObject);
begin
Form2:=TForm2.Create(Application);
Form2.Show;
Form2.Caption:='test'
//可以
end;

end.

 

A

ak_2004

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• 2005-07-25

• #3

implementation
uses Unit2;
{$R *.dfm}
procedure TForm1.OpenForm(aFormClass:TFormClass;Obj:TForm);
begin
Obj:=aFormClass.Create(Application);
//Application.CreateForm(aFormClass,Obj);
Obj.Show;
end;
procedure TForm1.BitBtn1Click(Sender: TObject);

begin
OpenForm(TForm2,Form2);
Form2.Caption:='test'
//不行 //这里的form2 不是用openform 建的form2即show出来的form,你看到的那个form2,其实指针已经释放了，只是对象没有释放，幸好你使用的是Create(Application)，不然它就没法管理了，就造成了内存泄漏，要达到你的效果
你必须使用function,把form2作为参数返回
end;

procedure TForm1.BitBtn2Click(Sender: TObject);
begin
Form2:=TForm2.Create(Application);
Form2.Show;
Form2.Caption:='test'
//可以
end;

end.

 

D

dreamisx

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• 2005-07-25

• #4

procedure TForm1.OpenForm(aFormClass:TFormClass;Obj:TForm);
改成procedure TForm1.OpenForm(aFormClass:TFormClass
var Obj:TForm);
OpenForm(TForm2,Form2);
改成OpenForm(TForm2,TForm(Form2));
试试。

 

W

wxfdage

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• 2005-07-25

• #5

同意楼上，参考这个代码
procedure TApplication.CreateForm(InstanceClass: TComponentClass
var Reference);
var
Instance: TComponent;
begin
Instance := TComponent(InstanceClass.NewInstance);
TComponent(Reference) := Instance;
try
Instance.Create(Self);
except
TComponent(Reference) := nil;
raise;
end;
if (FMainForm = nil) and (Instance is TForm) then
begin
TForm(Instance).HandleNeeded;
FMainForm := TForm(Instance);
end;
end;

 

P

publicnews

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• 2005-07-25

• #6

在过程内转换和或传递前转换哪种更好些
procedure TForm1.OpenForm(aFormClass:TFormClass;var Obj);
begin
TForm(Obj):=aFormClass.Create(Application);
TForm(Obj).Show;
end;

 

D

duhai_lee

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• 2005-07-25

• #7

在unit2 中 注册 窗体类就没有问题了. 如:
initialization
RegisterClass(TForm2);
finalization
UnRegisterClass(TForm2);

否则就有问题.

 

狐

狐狸也糊涂

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• 2005-07-25

• #8

原来如此，又了学了一招!谢谢。。。

 

P

publicnews

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• 2005-07-27

• #9

注册窗体类? 哪种执行效率要高呢?

 

W

wkh

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• 2005-08-04

• #10

procedure TForm1.OpenForm(aFormClass:TFormClass;var Obj:TForm)
//加入Var
begin
Obj:=aFormClass.Create(Application);
//Application.CreateForm(aFormClass,Obj);
Obj.Show;
end;

 

P

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• 2005-08-10

• #11

多人接受答案了。