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Key Concepts and Terminology

This section introduces the basic concepts and terminology that will help you get started in learning how to use Jamba.

What is Jamba?

Jamba is a visual authoring tool that lets you create interactive, multimedia Java™ applications. Java™ is a full-featured programming language and, in effect, Jamba lets you take advantage of this power without having to learn its complex commands and syntax. Because Java™ is available on a large variety of platforms, your Jamba applications can be played on these platforms using any Java-enabled browser.

The applications you create can be applets or applications. An applet is an application that runs within a Web browser, such as Netscape or Microsoft's Internet Explorer. An application does not run through a browser and is really no different from any other desktop application.

Basically, when you save your application, Jamba saves your work in three different formats. Each file format serves a different purpose. Consider an application that you create called myapp. When you save your application, Jamba actually saves myapp .jmb, myapp.html, and myapp.jtf.

The . jmb file is the information that you edit and potentially re-open and work with again in Jamba. The . html file is the HyperText Markup Language (HTML) file that you display in a Web browser. (Web pages are actually . html files). You can display the . html file in its entirety as a standalone application or you can incorporate it into an existing . html file if you want it to be part of another web page. The . jtf file is the Jamba text file that is called by the . html file. This is the information that actually displays the interactive multimedia objects at runtime.

Objects

Objects are the essential building blocks that make up your applications. Here are some examples of objects that you can use throughout your applications.

Push Button Objects

Push Buttons let you create the variety of buttons that you see in applications. Examples: OK, Cancel, and Next. The figure on the right shows an example of a Push Button.

Graphic Objects

Graphic objects let you display . gif and . jpg graphics. The graphics can be actual size, tiled, or clipped within a particular area. You can designate a color in the graphic to be transparent so that it won't show at runtime. Jamba lets you use special display effects on graphics and it also lets you do cell animation.

Audio Objects

Audio objects let you include . au sound files within your applications. You can set up audio so that it plays automatically, or when the user clicks on a button or some other type of object.

List Box Objects

List Boxes provide lists of text items from which the user can select by either clicking on an item and pressing Return or by double-clicking on an item. You decide the font and colors the object uses.

Text Field Objects

Text Field objects allow your applications to display editable text. If the object contains a large quantity of text that cannot be seen at once, the object automatically has scrollbars.

Text Objects

Text objects let you display non-editable text.

Browser Objects

Browser objects let you direct the Web browser to go to a different URL so that your application can display a different . HTML file.

This is just a sampling of the kinds of objects that come with Jamba. For detailed information on each type of object that comes with Jamba, see Chapter 6.

Pages

The blank background on which you place objects is called a page. Each Jamba application can contain one or more pages that are actually used as separate displays at runtime.

Hint: Often, applets that you intend to run on the Internet use only one page.

If your application contains multiple pages, the objects on one page are automatically removed from memory as soon as a subsequent page displays.

In addition to standard pages, Jamba allows you to create special pages called backgrounds. These background pages contain objects that you want to persist across the display of multiple standard pages. For example, if you want your application to play audio across multiple pages, you would put an Audio object on a background page.

Properties

All objects and pages have certain properties (characteristics) that you set in order to control their appearance. For example, a Push Button object has a property called Label that allows you to change the text label that appears on the button. If you want to create an OK button, you draw a Push Button object and set its Label property to OK. Similarly, you set a Graphic object's Filename property to specify the image that appears within the object. See Chapter 7 for a complete description of object properties.

Events and To Do Items

An event is a way in which an object can be affected at runtime. For example, a Push Button can have a Click event which occurs when a user clicks on the object. Similarly, a ListBox object can have a Select event occur when a user makes a selection from the object's list.

After you draw an object, you decide which events will cause it to perform a To Do item. For example you can set up a Graphic so that it does something for both a Click and a DoubleClick event. For every event that you choose, you specify one or more To Do items that occur as a result. For example, you can set up a Push Button to recognize a Click event. You can then set up the object so that its To Do item is to play an Audio object as soon as the Click event occurs. In another example, you might set up the Push Button so that when a Click event occurs, two To Do items take place: an Audio object plays and a Graphic object becomes visible to show a . gif file.

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