Property and Event Reference

Chapter 1 About Properties and Events

This chapter describes properties and events in SilverStream, including:

Understanding properties and events

You use properties and events to define the features and behaviors of objects you develop in the SilverStream Designers. They are part of the visual-programming toolset that SilverStream provides and their purpose is to give you a productive, consistent way to manipulate more complex and varied implementation details.

How they relate to the SilverStream API

Properties and events are separate from the SilverStream API. The properties and events you specify for a particular Designer object turn into metadata that tells SilverStream how to generate and operate that object. Often this results in method calls to a corresponding class in the SilverStream API, but not always.

A closer look at properties

Properties are attributes that you set at design time for a particular Designer object, such as a form or page. You specify them in the Designer's Property Inspector dialog. For instance, here are the properties for a label control on a page:

Overriding properties at runtime

Because properties are not part of the SilverStream API, you can't access them directly at runtime like instance variables (fields). But for many properties, the API does provide accessor (get and set) methods that enable you to read and modify those property values.

Example

In the previous illustration, the Enable HTML Generation property is checked at design time to specify that you want the HTML for the lblSamples control generated on the page. But suppose you need to do a runtime test (maybe based on user authority) and dynamically turn off HTML generation of that label.

If you look at the API methods for the corresponding SilverStream class (AgpLabel), you'll find you can code:

getEnableHTMLGeneration() to find out whether HTML generation is currently enabled
setEnableHTMLGeneration() to turn HTML generation on or off

A closer look at events

Events correspond to event-handler methods that the Designers provide for forms, pages, and other objects. To perform the processing you want for a particular object, you use the Programming Editor to write code in its appropriate event-handler methods. For instance, here are the events for a button control on a form:

Notice that the actionPerformed event for the Save button corresponds to the event-handler method handle_Save_actionPerformed(). The code you write here will execute when a user clicks that button.

Under the covers

Events are implemented in a couple of ways:

Some events correspond to methods of a base class in the SilverStream API. An example of this is pageGenerateBegin() for a page (the AgpPage class).
Other events correspond to methods of a listener interface in the SilverStream or Java API. For instance, the actionPerformed event corresponds to the actionPerformed() method of the ActionListener interface.

Earlier you saw an example of the actionPerformed event, yet the method involved was not actionPerformed() but handle_Save_actionPerformed(). That's because SilverStream automatically generates actionPerformed() and dispatches calls to methods named handle_ControlName_actionPerformed().

Finding properties and events

You can use the SilverStream help system to get reference information about the properties and events for:

Pages and their controls
Forms and their controls

Here's how to find that information:

If you

See

Know the name of the property or event you want

One of these chapters in the Property and Event Reference:

Page Properties

Page Events

Form Properties

Form Events

Want a list of the properties and events associated with a particular class in the SilverStream API

The documentation for that class in the SilverStream API help

Want a list of the properties and events for a particular Designer object (such as a form, page, or control)

This chapter in the General Reference: Designer Objects and their API Classes

You can use it to:

Find the SilverStream API class that corresponds to your Designer object

Go to the documentation for that class in the SilverStream API help and see the list of its associated properties and events

If you	See
Know the name of the property or event you want	One of these chapters in the Property and Event Reference: Page Properties Page Events Form Properties Form Events
Want a list of the properties and events associated with a particular class in the SilverStream API	The documentation for that class in the SilverStream API help
Want a list of the properties and events for a particular Designer object (such as a form, page, or control)	This chapter in the General Reference: Designer Objects and their API Classes You can use it to: Find the SilverStream API class that corresponds to your Designer object Go to the documentation for that class in the SilverStream API help and see the list of its associated properties and events