Developing a Web-based application for the Palm OS is a fast and relatively painless way to reach a whole new market of wireless device users. Not only are Palm devices quite popular with users, but they provide us developers with additional resources to play with. Compared to other wireless devices, such as WAP-enabled phones, many of the restrictions you are subjected to are no longer relevant. For example, screens are larger on Palm devices and there's a stylus to help with most input needs.
A Web clipping application "scrapes" content from other sites or from databases and "posts" that information into an HTML page that is easily read by the Palm. Web clipping applications rely heavily on HTML skills that you already have, without little modification. Of course, you cannot use frames or Flash movies, but at least you can create forms with inputs that extend to fill an entire line.
In this 10-Minute Solution I'll take a quick look at how to get your feet wet in creating static content for Palm devices.
Getting Set Up
The Palm OS comes with a utility that does a great deal of the hard, behind-the-scenes work automatically. This gives you the liberty of designing, quite honestly, a basic HTML page and then using Palm's utilities to translate it into an application format that is readily usable by Palm devices.
Two quick downloads can greatly facilitate your development and testing process: the Query Application Builder (QAB) "compiles" the HTML you develop in the actual Web clipping application, and the Palm OS Emulator (or POSE) allows you to test your app once you're through developing it. (There's a QAB in Zip format that you can download here.) If you already have a variety of Palm devices available to you, the POSE isn't really necessary because you can simply install your app on those devices through the HotSync installation manager. Refer to your user's guide for additional information on how to do that.
Writing the App's Index Page
Now you're ready to set up a basic HTML page. This page will serve as the "index" for your application—its front page. From here, you can include information about who you are (company information), what you do (the purpose of the application), or even the content itself (dynamically generated using server-side scripts). For the purpose of this basic demonstration, your Web app is going to provide some simple static content. In the beginning, you should be more concerned with becoming familiar with the tools used to compile the application, rather than how to generate pages dynamically using server-side scripting languages.
Here you can write your very basic HTML page, using standard HTML 3.2, keeping in mind some quick design concerns:
- Page weight is very important when dealing with wireless devices. Your "customers," the users of your application, are charged per kilobyte of information that is sent both ways. This is the double whammy of using Palm.net's service. Sending and receiving information counts against Palm.net's customers' quota for the month. So you will best serve them by keeping information short and relevant. Additionally, this includes HTTP post variable names, which is sometimes overlooked as a way to trim down the bandwidth used as much as possible.
- Screen size, while larger than WAP-enabled phones, is still not unlimited. Keep the requested information buried as "shallow" as possible in the application. This ensures that your users won't be sending and receiving unnecessary pages to get to the information they want.
With that in mind, you can create your HTML file:
<HEAD>
<TITLE>WebApps, Inc.</TITLE>
<META name="PalmLauncherRevision" content="1.0">
<META name="PalmComputingPlatform" content="true">
<META name="HistoryListText" content="true">
</HEAD>
<BODY>
WebApps, Inc. <br>
Bringing the Web to your Palm! <br>
</BODY>
</HTML>
There are a couple of things to mention here. First, you can see that the PalmOS uses pretty standard HTML 3.2. You can find the HTML 3.2 DTD for Palm devices on Palm's development site.
Second, notice that there are some unique META tags. A brief description of each is in order:
- PalmLauncherRevision is the version number of your application. Put this META tag on your primary index page. This gives your entire application a version number that can later be referenced by your users to see if an upgrade to the latest version is required.
- PalmComputingPlatform lets the QAB know that you are building an application for the Palm OS, which will enact some stricter rules regarding image size and formatting than you'd need for an ordinary Web page.
- HistoryListText allows your history cache to record where you are in your application and present that information from the drop-down history menu, available on the Palm.
From here, you are able to start up the QAB and begin compiling your Palm Query Application (PQA).
Compiling the Application
The steps to compiling your application are actually fairly straightforward. Start first by launching the PQA Builder:
Select File > Open Index to find the index file for your app's primary index.html page:
After selecting the file and clicking the Open button, the QAB will accepted your index file and be ready to build the application:
Choose File > Build PQA to begin building the actual application. You may notice that I only show one file, but you can assume that in larger applications there would be several files.
The Build PQA dialog box gives you the ability to set some final configurations to your application. You can set both large and small icons. Also, you can give your application a more descriptive name and determine where it is going to be saved. Here, it is set to go directly to the Windows desktop.
After clicking Build, your application will be built. Because I have no association on my computer with .PQA files, nor did I specify an icon during the build phase, I get the standard unknown file type icon in Windows. If you specify an icon during the build phase, the icon you indicate would appear here instead:
This PQA can be installed and tested either on your POSE emulator or on your Palm device(s).
Now that you know about some of the tools available to make Palm OS–based Web clipping applications, you can experiment with developing some of your own.
The real exciting development work is in making dynamic content, of course, not static content. By using a variety of server-side scripting languages, however, you can generate any appropriate content and present it in HTML 3.2 format to build your app.
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