FoxPro Barcode FAQ & Tutorial
In this FoxPro Barcode FAQ and tutorial, IDAutomation presents
a few methods for using the Barcode ActiveX Control and Barcode Fonts in
Microsoft Visual FoxPro 6 forms and reports.
- Using self checking barcode fonts such as Code
39
- Using Barcode Fonts with the Program Module for
barcode fonts requiring check digits such as Code 128, Postnet, Interleaved
2 of 5 and UPC
- Using the Barcode ActiveX Control
- Resolving version issues with the Barcode ActiveX
Control
Self-Checking
Barcode Fonts, MICR
and OCR fonts are compatible
with FoxPro and may be used with ease. To use a self-checking font such
as Code 39, an asterisk
"*" will need to be inserted before and after the bar code data encoded.
Therefore, when encoding TEST3OF9 in a barcode, the text will be
displayed as *TEST3OF9* in a label on form or in a field in report.
The Code 39 font should be selected for label on form or for field in report.
- In this example, a dynamic Code 39 barcode field will be added to
a Visual FoxPro 6.0 report with IDAutomation's
Code 39 barcode
font. The sample assumes that the data to be encoded in the barcode
is stored in the "Code" field of character type in the "Items" table.
- First, install one of IDAutomation's Code 39 barcode font packages
by downloading
a demo or
ordering a
license.
- Open the report for editing. Select the "Field" button in the report
controls toolbar and click on the report layout where the bar code should
be displayed. This will open a dialog box for specifying the properties
for new report field. In this example, the Code field content is the
one selected to include in the barcode. Because the start and stop characters
required for Code 39 need to be added, the following expression in the
dialog box for report field properties needs to be entered.
- Resize the new field to the required size of the field. With the
field selected, choose Format - Font... in menu and choose
one of the Code 39 Barcode Fonts. In this example, the IDAutomationHC39S
font is used, which is a "human readable" font provided in the
Code 39 Font Advantage
Package. In this example, Format - Align - Center
Horizontally and Center Vertically is chosen
so the barcode will appear in the middle of the field and then change
the font size to 14 so it can be easily scanned.
- Now, when the Items table is prepared and contains some data, preview
of the report should display a bar code in the Barcode column in the
report.
- The process to display a barcode on the form using barcode fonts
will require some coding. To do this, put a TextBox control on the form,
specify .T. for ReadOnly property for it, then set the Font for displaying
to the Barcode font with size 14. Set the Alignment property to "2 -
Center". After that, specify the expression for displaying in the ControlSource
property of the text box. This is not possible in design time, so it
needs to be assigned in run time.
LICENSE NOTICE: This source code may be incorporated in an application
only if a valid license from IDAutomation.com, Inc. is acquired for the
associated font and the copyright notices are not removed from the source
code. Redistribution of IDAutomation's fonts and components requires a Developer
License.
- The program module and source code for FoxPro calculates the start,
stop and check digits for the barcode and returns a character string,
that when combined with the barcode font, creates a correct barcode.
- Download the
IDAutomation-prg.txt file and save it as IDAutomation.PRG.
- Add this file as a program module to the VFP project, set it as
a procedure file using SET PROCEDURE TO... ADDITIVE command somewhere
in the main (startup) code of the project and access the function in
the application as necessary. This is demonstrated in the following
Visual FoxPro Barcode Sample Project.
- Place the appropriate expression in the dialog box for report field
properties. For example, when using the Code 128 barcode font, call
a code 128 function defined in the program module. There is not really
much difference in defining properties in this method compared to
Method 1, except the expression
is now a function defined in our program module.
- To use it on form, in design time select the "ActiveX Control (OleControl)"
on the Form Control toolbar and click on the form. After the "Insert
Object" dialog box opens, select "Insert Control" option. In the list
of all installed ActiveX controls, select a control to use that begins
with "IDautomation".
- The characteristics can then be modified in the properties window.
- To print barcodes on reports or labels, the Barcode ActiveX control
should be embedded and prepared in the table field of type General,
and then displayed in the report. This will require some programming
of code for preparing the Barcode ActiveX control in General field.
- Assume the same data table as in Method 1.
Add to the table the field of type General called "CodeGen".
- To display it in a report, put the Picture/ActiveX Bound Control,
then select the "File" option and specify General field and name in
it ("Items.CodeGen").
- Then, prepare the code that will populate the General field by the
Barcode ActiveX control with appropriate data from the Code field for
each record in the Items table. This code should run before printing.
This can be organized by one of the following ways:
- Define code in the custom program that calls a report, such as
in the
VFP barcode example.
- Define code in the BeforeOpenTables event of the data environment
in the report: right click on the report in report designer window,
select "Data Environment" menu item, double click on data environment
window and write the code there, for example in the picture below.
- The code might be a bit complex and require use of a custom form.
The code displayed in above picture may be acquired
here or
download
the VFP barcode example for an implementation created in VFP
6.0, which demonstrates how to store the BarCode ActiveX in the field
of General type, display it on a form and print. The sample also includes
a simple code to demonstrate how to prepare appearance and properties
for the ActiveX control embedded in General field before printing.
Resolving Version Issues with ActiveX
If a different version of the Barcode ActiveX Control is installed, errors
may appear in the existing Visual FoxPro application making use of the ActiveX
Control. One of the following suggestions below may resolve this issue:
If the form with the Barcode ActiveX on it does not open after installing
a new version of the ActiveX control:
The best way to fix this problem is to install a previous version of
ActiveX control again. Then open the VFP form and remember or write down
all property settings for BarCode ActiveX control (right-click on properties
window and select the "Non-Default Properties Only" option that will list
all properties for which values should be remembered). Remove the ActiveX
control from the form and save the form. Close the VFP development environment.
Install the new version of the ActiveX control. Open the form, put the ActiveX
control on the form again and specify property values in exactly the same
way. Of course, this will require recompiling of the VFP application.
The form code may also be changed to enable the ActiveX control in code
during run time, as in the
VFP barcode
example. If the ActiveX control is created and property values assigned
at run-time, different versions of ActiveX on the form will work with the
same code.
If
the Barcode ActiveX stored in fields of General type causes an error when
trying to use it:
After installing a different ActiveX control version, another program
should create a new ActiveX control in general field and set property values
accordingly. This will not require recompiling the application - only the
data needs to be updated.
In the
VFP barcode example, there will be a sample of the report printed using
a dynamically prepared ActiveX control in General fields with sample of
setting properties for it. It is recommended to use this approach so a different
version of the control will not cause problems.
Special thanks to Vlad Grynchyshyn for providing information on using
the Barcode ActiveX Control in FoxPro.
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