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Build Cross-Platform PDA Apps

Posted June 4, 2004

AppForge Crossfire 5.0 is a comprehensive add-in to VS.NET 2003 for creating Windows Mobile 2003, Pocket PC, Palm OS, and Symbian OS applications. According to AppForge, these applications will run on more than 90 percent of the world's handheld, mobile, and wireless devices (see Figure 1). One VB.NET code base contains your logic and business-rules code. Then, you can adapt the UI (forms) to the dimensions and capabilities of ARM-based Pocket PC, Nokia Series 60, Sony Ericsson P800/P900, and Palm OS devices. Crossfire's virtual machines or "boosters" let you run your code on the supported hardware. Crossfire makes resources work across platforms, and in a common format, by including utilities that convert Access databases, TrueType fonts, images, and AVI movies to its own format.

You'll see a new project template called "Crossfire Application," an AppForge menu, toolbars, and a new toolbox category in your IDE after you run the straightforward setup routine. VS.NET developers will be right at home with the Crossfire tools, but you'll find far more than grids, buttons, and data connections. For example, the toolbox includes a control to support built-in cameras and a signature-capture component.

Sample solutions give you a quick grasp of Crossfire's concepts and capabilities. (However, the online Help could use more tutorial depth.) The online Stock Quote example shows how to use common modules and conditional compilation to include fonts and sockets appropriate for the target device or platform. It connects over the Internet to retrieve delayed stock updates and trends.

Deploying an application with its booster over ActiveSync is as simple as clicking on a menu item in the IDE and watching the progress in the VS.NET output window. You distribute apps to end users by selecting the target device from the Build Installation File menu to create a Pocket PC (CAB), Palm OS (PCR), or Symbian OS (SIS) file.

The design-time experience is good but not foolproof. For example, the designer uses the native WinForms form control, which allows an invalid color value (desktop) and causes a runtime error. A basic representation of the target screens launches quickly when you run a Crossfire-based app within VS.NET, but it's low-fidelity compared with a real device. It would be nice if Crossfire simulated all of a PDA's input modes within the IDE.

Despite these minor shortcomings, Crossfire is a solid product that makes it easy, practical, and enjoyable to create one base application and—with relatively little effort—extend its reach to a wider range of devices on non-Windows platforms.

Crossfire 5.0
AppForge
Web: www.appforge.com
Phone: 800-637-5740; 678-686-9400
Price: $1,070
Quick Facts: Sophisticated add-in to VS.NET for developing VB.NET applications for Windows Mobile 2003, Pocket PC, Palm OS, and Symbian OS handheld devices.
Pros: Easy to use and deploy; wide range of controls; solid samples; supports major communications protocols; includes conversion tools for resources and data.
Cons: Device simulation in IDE lacks fidelity and input mode support; documentation has rough edges.

About the Author
Ken Cox is a programming writer and VB.NET developer in Toronto building e-commerce Web applications and XML Web services. Ken is a Microsoft MVP for ASP.NET. Reach him at .