BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How do I dynamically create a VCL component          BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) View previous topic :: View next topic   Author Message William Riley Guest Posted: Fri Sep 15, 2006 12:36 am    Post subject: How do I dynamically create a VCL component Builders, I am trying to dynamically create a VCL component and cannot seem to get it to work. The code compiles and seems to run fine but I cannot see the component on the form. The Borland C++ Builder Development Guide seems to indicate that this can be done but is short on details. My understanding of C++ Builder get to be more every day but certainly there is something I do not understand about this and maybe doing something stupid; I suspect it may have something to do with the Component Owner parameter which I have set to this (Form1). I have included the code below. Any help, comment and suggestions appreciated. //--------------------------------------------------------------------------- #include <vcl.h> #pragma hdrstop #include "dynamicComponentTest.h" //--------------------------------------------------------------------------- #pragma package(smart_init) #pragma resource "*.dfm" TForm1 *Form1; //--------------------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { } //--------------------------------------------------------------------------- void __fastcall TForm1::OnCreateFormEventHandler(TObject *Sender) { dynamicTEditComponent = new TEdit(this); } //--------------------------------------------------------------------------- void __fastcall TForm1::OnCloseFormEventHandler(TObject *Sender, TCloseAction &Action) { delete dynamicTEditComponent; } //--------------------------------------------------------------------------- void __fastcall TForm1::OnPaintFormEventHandler(TObject *Sender) { dynamicTEditComponent->Top = ClientHeight/2; dynamicTEditComponent->Left = ClientWidth/2; dynamicTEditComponent->Height = 20; dynamicTEditComponent->Width = 80; // Make sure it we can see it if it is painted to form dynamicTEditComponent->Color = clRed; dynamicTEditComponent->Text = "Dynamic TEdit Component"; dynamicTEditComponent->Show(); dynamicTEditComponent->Repaint(); // but I can't see it } //--------------------------------------------------------------------------- Back to top JD Guest Posted: Fri Sep 15, 2006 1:01 am    Post subject: Re: How do I dynamically create a VCL component "William Riley" <William_R1 (AT) verifone (DOT) com> wrote: Quote: You never set it's Parent property. ~ JD Back to top Remy Lebeau (TeamB) Guest Posted: Fri Sep 15, 2006 1:04 am    Post subject: Re: How do I dynamically create a VCL component "William Riley" <William_R1 (AT) verifone (DOT) com> wrote in message news:4509af4a$1 (AT) newsgroups (DOT) borland.com... Quote: I am trying to dynamically create a VCL component and cannot seem to get it to work. The code compiles and seems to run fine but I cannot see the component on the form. That is because you are making a classic newbie mistake - you are not setting the Parent property. Quote: I suspect it may have something to do with the Component Owner parameter which I have set to this (Form1). The Owner has nothing to do with the component's visibility. The Owner manages the component's memory, nothing else. The Parent is who controls where the component is positioned visually, and whether the component can be interested with. Quote: void __fastcall TForm1::OnCreateFormEventHandler(TObject *Sender) Do not use the OnCreate event in C++. It is a Delphi idiom that produces illegal behavior in C++, as it can be triggered before the constructor. Use the actual constructor instead. The same applies to the OnDestroy event. It can be triggered after the destructor, which is also illegal in C++. Use the actual destructor instead. Quote: void __fastcall TForm1::OnCloseFormEventHandler(TObject *Sender, TCloseAction &Action) { delete dynamicTEditComponent; } Strictly speaking, you do not need to delete Owned components. They are automatically freed when their Owner is freed. Quote: void __fastcall TForm1::OnPaintFormEventHandler(TObject *Sender) Do not use the OnPaint event like that. You should be setting the TEdit's properties at the time that you create it, not every time the form is re-painted (the OnPaint event is triggered many times during the form's lifetime): __fastcall TForm1::TForm1(TComponent *Owner) : TForm(Owner) { dynamicTEditComponent = new TEdit(this); dynamicTEditComponent->Parent = this; // <-- add this!! dynamicTEditComponent->SetBounds(ClientWidth/2, ClientHeight/2, 80, 20); dynamicTEditComponent->Color = clRed; dynamicTEditComponent->Text = "Dynamic TEdit Component"; } Gambit Back to top William Riley Guest Posted: Fri Sep 15, 2006 2:12 am    Post subject: Re: How do I dynamically create a VCL component Thanks for the info and helpful tips. I moved the dynamic TEdit creation to form constructor and set the control Parent property to this and things appear to be working fine. I agree about the setting of TEdit properties in OnPaint event but wanted to make sure something was not getting reset behind my back until I could figure out what was going on. BTW any suggestions for reference material I can find or buy to better understand the Borland C++ Builder. There are only a couple books I have found and the one Borland C++ Builder Developer Guide published by H SAMS (not sure of the exact title) is not all that enlightening. It basically makes me aware that certain features exist but I end up plowing through the C++ Builder help files and trying a lot of code; not very efficient. "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:4509b65e$1 (AT) newsgroups (DOT) borland.com... Quote: "William Riley" <William_R1 (AT) verifone (DOT) com> wrote in message news:4509af4a$1 (AT) newsgroups (DOT) borland.com... I am trying to dynamically create a VCL component and cannot seem to get it to work. The code compiles and seems to run fine but I cannot see the component on the form. That is because you are making a classic newbie mistake - you are not setting the Parent property. I suspect it may have something to do with the Component Owner parameter which I have set to this (Form1). The Owner has nothing to do with the component's visibility. The Owner manages the component's memory, nothing else. The Parent is who controls where the component is positioned visually, and whether the component can be interested with. void __fastcall TForm1::OnCreateFormEventHandler(TObject *Sender) Do not use the OnCreate event in C++. It is a Delphi idiom that produces illegal behavior in C++, as it can be triggered before the constructor. Use the actual constructor instead. The same applies to the OnDestroy event. It can be triggered after the destructor, which is also illegal in C++. Use the actual destructor instead. void __fastcall TForm1::OnCloseFormEventHandler(TObject *Sender, TCloseAction &Action) { delete dynamicTEditComponent; } Strictly speaking, you do not need to delete Owned components. They are automatically freed when their Owner is freed. void __fastcall TForm1::OnPaintFormEventHandler(TObject *Sender) Do not use the OnPaint event like that. You should be setting the TEdit's properties at the time that you create it, not every time the form is re-painted (the OnPaint event is triggered many times during the form's lifetime): __fastcall TForm1::TForm1(TComponent *Owner) : TForm(Owner) { dynamicTEditComponent = new TEdit(this); dynamicTEditComponent->Parent = this; // <-- add this!! dynamicTEditComponent->SetBounds(ClientWidth/2, ClientHeight/2, 80, 20); dynamicTEditComponent->Color = clRed; dynamicTEditComponent->Text = "Dynamic TEdit Component"; } Gambit Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.