VHP Computing Group. Creeping line class.





						15 September, 2000 Vladimir Trukhin Senior Software Engineer JSC "Votkinsk Hydroelectric Power Plant" Fax: +7 (34241) 63297 E-mail: vlt@votges.ru Creeping line. The Problem Visual FoxPro supplies developer with a full set of controls for a screen forms creation. However, sometimes you need create a vivid and showy form. In this case it is appropriate to use such elements as animated images, creeping line and etc. Unfortunately FoxPro has not classes, which would be designed for such use. As a result of it many developers find and use ActiveX controls. Usage of ActiveX occasionally is very problematically, especially in Visual FoxPro. You may have problem when you try to implant element into a form or when you want to distribute an application. The Solution. In many cases a search of appropriate ActiveX control is not best choice. You can try to create your own class based on Visual FoxPro base classes. This class will have the wanted properties and the required methods. Let's take up a creation of such class. It may be a Creeping Line class. Firstly, we must form requirements to new class. For example they are: An object of the class must be easy to place itself on a form like Label class. It must have properties of Label class It must have additional properties and methods controlling speed, start and stop of the Creeping Line. Secondly, we need to choose a correct base class. From the generated requirements it is visible, that the new class should inherit properties of Label class and Timer class. We choose Container class as base class to implement such inheritance. It allows us to encapsulate the Label object and the Timer object into Creeping Line class. So, we can define a set of properties and methods for our class: Methods: Stop(), Start() Properties: Interval, FontName, FontSize, FontBold, FontItalic, ForeColor, Alignment. Class defination: DEFINE CLASS runline AS container Width = 158 Height = 28 BackStyle = 0 BorderWidth = 0 Name = "runline" -- Specifies the text displayed in an object's caption. caption = ‘’ -- Specifies if the text is italic. fontitalic = .F. -- Specifies if the text is bold. fontbold = .F. -- Specifies the font size for text displayed with an object. fontsize = 10 -- Specifies the name of the font used to display text. fontname = 'Arial' -- Specifies the number of milliseconds between -- calls to a Timer control's Timer event. interval = 500 -- Specifies the alignment of text associated with a control. alignment = 0 ADD OBJECT text AS label WITH ; AutoSize = .F., ; BackStyle = 0, ; Caption = "Label1", ; Height = 17, ; Left = 0, ; Top = 6, ; Width = 40, ; Name = "Text" ADD OBJECT timer AS timer WITH ; Top = 3, ; Left = 129, ; Height = 23, ; Width = 23, ; Interval = 500, ; Name = "Timer" PROCEDURE caption_access RETURN THIS.Text.Caption ENDPROC PROCEDURE caption_assign LPARAMETERS vNewVal THIS.Text.Caption = m.vNewVal ENDPROC PROCEDURE forecolor_access RETURN THIS.Text.ForeColor ENDPROC PROCEDURE forecolor_assign LPARAMETERS vNewVal THIS.Text.ForeColor = m.vNewVal ENDPROC PROCEDURE fontitalic_access RETURN THIS.Text.FontItalic ENDPROC PROCEDURE fontitalic_assign LPARAMETERS vNewVal THIS.Text.FontItalic = m.vNewVal ENDPROC PROCEDURE fontbold_access RETURN THIS.Text.FontBold ENDPROC PROCEDURE fontbold_assign LPARAMETERS vNewVal THIS.Text.FontBold = m.vNewVal ENDPROC PROCEDURE fontsize_access RETURN THIS.Text.FontSize ENDPROC PROCEDURE fontsize_assign LPARAMETERS vNewVal THIS.Text.FontSize = m.vNewVal ENDPROC PROCEDURE fontname_access RETURN THIS.Text.FontName ENDPROC PROCEDURE fontname_assign LPARAMETERS vNewVal THIS.Text.FontName = m.vNewVal ENDPROC PROCEDURE interval_access RETURN THIS.Timer.Interval ENDPROC PROCEDURE interval_assign LPARAMETERS vNewVal THIS.Timer.Interval = m.vNewVal ENDPROC PROCEDURE start THIS.Timer.Enabled=.T. ENDPROC PROCEDURE stop THIS.Timer.Enabled=.F. ENDPROC PROCEDURE alignment_access RETURN THIS.Text.Alignment ENDPROC PROCEDURE alignment_assign LPARAMETERS vNewVal THIS.Text.Alignment = m.vNewVal ENDPROC PROCEDURE Init THIS.text.Width=THIS.Width THIS.text.Height=THIS.Height ENDPROC PROCEDURE timer.Timer LOCAL lcFirstChar, lcSubLine lcFirstChar=SUBSTR(THIS.PARENT.Text.Caption,1,1) lcSubLine=SUBSTR(THIS.PARENT.Text.Caption,2) THIS.PARENT.Text.Caption=lcSubLine+lcFirstChar ENDPROC ENDDEFINE The Conclusion Created class is easy to be placed on a form and to be controlled by an application. It works like standard Visual FoxPro classes. You can download the article and program sample from file: runline.zip Size: 19KB. There is a Russian version of article in file artl003r.zip Size: 13KB. Home Page \| Technologies \| Specialists \| Download \| Links \| Sign Guestbook \| View Guestbook