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Palm Development with MobileVB

Palm Development with MobileVB

eveloping applications for the Palm OS may seem like a daunting task to a VB developer. The traditional Palm SDK requires at least moderate knowledge of the C programming language and has a substantial learning curve. Further complicating the situation are the memory management requirements of the Palm OS and its specific API references. Now, in version 3.5, MobileVB is a well thought-out add-in for VB6 that alleviates the drawn-out development process and makes Palm OS programming a viable option for even novice VB programmers. Enhancing development effectiveness, MobileVB allows VB programmers to take advantage of existing skills without the need to learn a new programming language or another IDE.

MobileVB requires Visual Basic 6.0 with Service Pack 5 or higher. There is a free trial version of MobileVB at the AppForge Web site, www.appforge.com. You can download the free trial to follow along with this article, and because the installation process is painless, I’ll skip over these minor steps and focus on how MobileVB is used within the Visual Basic IDE.

Getting Started with MobileVB
Developing a Palm OS project in MobileVB is straightforward, although if you have developed in VB before, you will find a few items that are slightly out of the ordinary. For starters, the manner in which you start VB is important. Rather than using your existing desktop icons or Start Menu shortcut, MobileVB installs its own icons. You will find these on your desktop after installation, and in the Start Menu located in the AppForge MobileVB folder.

When you start MobileVB using one of its icons, you are given options for creating several types of applications. This option window can be seen in Figure 1. Along with the Palm OS, MobileVB provides templates for the Pocket PC, Symbian P800, and the Nokia Communicator. I’m interested in the Palm OS for this tutorial, but the basic concepts are the same for all of the devices.

Figure 2: Access to a variety of new controls on the General tab.

MobileVB Controls
When you create a Palm OS project, MobileVB creates a blank form with the correct size for a Palm OS device. You may be tempted to begin developing a project by dragging and dropping the intrinsic VB controls, as you would normally do with a traditional Visual Basic project. But if you look further, you will see an entirely new set of controls in the General tab of your toolbox (See Figure 2). It is with these newly available controls (AppForge calls them Ingots) that you will devise your interface and construct your project.

Often, these controls provide a greater set of functions than their VB counterparts, making them much more powerful than the intrinsic controls. Table 1 details the MobileVB controls:

Table 1: Sorting out the MobileVB Ingots (controls).

MobileVB Control Name

What it does…

AFTextBox

Like its VB counterpart

AFComboBox

Reads textual input and/or prompts the user to select an item from a menu

AFListBox

Displays a list of varying size and content; the user can select one or more of the items in the list box to provide input

AFGrid

Displays text in a spreadsheet-like control from which the user can select one or more grid elements to provide input

AFLabel

Used like the standard VB label control

AFGraphicButton

Provides standard button options but can display a picture instead of a shape

AFButton

Similar to the VB CommandButton control

AFCheckBox

Provides a True/False option

AFRadioButton

Provides the option of selecting exactly one item from a list of items

AFGraphic

Displays graphics on the screen; uses the MobileVB Graphic Converter to create a proprietary .rgx or .jpg image

AFShape

Draws rectangles, squares, circles, and ovals

AFFilmstrip

Animates a series of graphics on the screen

AFMovie

Displays a movie on the screen after it has been converted from AVI to RMV

AFHScrollBar

Places a horizontal scrollbar on the form

AFVScrollBar

Places a vertical scrollbar on the form

AFSlider

Allows user input or output based on magnitude.

AFTone

Plays simple musical tones

AFScanner

Provides barcodes scanning in a variety of formats

AFSerial

Sends and receives data through a serial port

AFInetHTTP

Connects to the Internet

AFSignatureCapture

Reads signatures, stored as String data, for user input

AFClientSocket

Provides a variety of functions for performing socket-based communication

Sprite Field

Controls sprites and receives events during game progress

Sprite Control

A non-visual Ingot that eases sprites

AFTimer

Like the standard Timer, used to execute code at intervals

The VB IDE can become cluttered with the new controls, so if you prefer, you can create a new tab to which you can copy the MobileVB Ingots. To create the MobileVB tab, right-click on the General tab, select Add Tab and then name the new tab. Notice the small yellow letter “i” that allows you to distinguish between standard controls and MobileVB controls. You can now move the MobileVB controls by dragging and dropping them to the new tab.

The remaining IDE, including the Form Layout window, Property window, Project Explorer, and menus, continues to function as you would expect, although MobileVB adds an additional AppForge-specific menu with the following functions (Table 2).

Table 2: AppForge adds another menu with specific functionality to the Visual Basic IDE.

AppForge-specific Menu Item

What it does…

Database Converter

Converts Microsoft Access database tables to the Palm Database (.pdb) format and generates a VB code module for the database, providing an interface for accessing and modifying the Palm Database

PDB Database Viewer

Displays the internal schema and data records in the Palm Database file. Also displays other useful information, including the internal database name, CreatorID, and TypeID of the database, and the number of records in the database

Font Converter

Converts TrueType fonts (ttf) into AppForge fonts (cmf)

Font Viewer

Displays the properties and characters for AppForge fonts

Graphic Converter

Converts bitmap files (bmp) into AppForge graphic files (rgx).

Graphic Viewer

Allows you to view AppForge graphic files (rgx)

Movie Converter

Converts AVI movies to AppForge movie files (RMV)

Movie Viewer

Allows you to view RMV movies

Universal Conduit Configuration

Configures a conduit for your application

Compile and Validate

Compiles and checks code for error

Deploy to Device

Uploads a compiled project to a handheld device

AppForge Settings

Applies the settings for an AppForge project

Open Project

Opens AppForge projects

Zoom Level

Opens a Zoom window, allowing you to view forms in a larger format

Creating a New Database Application with MobileVB

Writing Some Code
The module you added to the project contains all the necessary code for directly accessing the Palm Database, leaving you responsible for adding the appropriate code in the VB events. When the button Ingots are clicked, an event is raised. Using these events, it’s easy to add records, navigate the existing records, or delete records. Begin with the creation of a new record, which occurs when btnNew is clicked.

Along with the Palm OS, MobileVB provides templates for the Pocket PC, Symbian P800, and the Nokia Communicator.

Begin by opening the Code window to create a variable called NewRecord. The variable should be of type Boolean; that is, it holds a yes/no, true/false, or 1/0 value. Inside the btnNew_Click event, begin by setting the NewRecord variable to True. Next, set txtItem and txtQuantity to “”. You’ll be setting the TextBoxes to “” on several occasions and with that in mind, create a new procedure called ClearDisplay to set them. Then call the procedures as needed. The following procedures are finished:

   Private NewRecord As Boolean   Private Sub btnNew_Click()       NewRecord = True       ClearDisplay   End Sub   Private Sub ClearDisplay()     txtQuantity.Text = ""     txtItem.Text = ""   End Sub

Next, handle the forward and back (<- and ->) buttons. The code is nearly identical for both items and looks like this:

   Private Sub btnBack_Click()       PDBMovePrev dbInv       DisplayInfo   End Sub   Private Sub btnNext_Click()       PDBMoveNext dbInv       DisplayInfo   End Sub

The next item is the btnDelete code. Again, it uses the ClearDisplay sub procedure and the NewRecord variable. It checks to see if there is a record, and if so, deletes it. Here is the code:

   Private Sub btnDelete_Click()       If NewRecord Then           ClearDisplay           NewRecord = False           DisplayInfo       ElseIf PDBNumRecords(dbInv) > 0 Then           PDBDeleteRecord dbInv           DisplayInfo       Else           MsgBox "No records to delete"       End If   End Sub

Before moving on, let’s look at the Form_Load event. This event checks to see if the database exists and if not, creates a new one. You’ll also move to the first record in the database. The code you need is in Listing 1.

At the end, the Form_Load event calls the DisplayInfo sub procedure. This procedure (in Listing 1) contains the code that actually displays the information on the screen. You only have two buttons left to deal with. The first is btnSave, which saves the database record you currently have displayed, and btnExit, which causes the program to end. The following procedures finish the application:

   Private Sub btnSave_Click()       Dim MyRecord As tInvRecord       If NewRecord Then           PDBCreateRecordBySchema dbInv       End If       MyRecord.Item = txtItem.Text       MyRecord.Quantity = txtQuantity.Text       PDBEditRecord dbInv       WriteInvRecord MyRecord       PDBUpdateRecord dbInv       DisplayInfo   End Sub   Private Sub btnExit_Click()       Unload Me   End Sub

MobileVB does a splendid job of integrating Palm development into the VB IDE, and is undoubtedly one of the easiest to use all-around development tools available for the Palm. The tools are especially easy to use for developers that are already experienced with VB, as the learning curve is nearly nonexistent. If you are a VB developer and want to write software for mobile devices like the Palm OS, look no further.

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