Events

Each java-bean fires its own set of events. Event definitions and Event names are stored in the definition files created by the cpgen utility.

Event definitions are comment entries with the following structure:

*> eventClass event definitions, Class: classReference.

Event names are level 78 integers.

78 eventName VALUE eventIdValue.

In order to reduce the program complexity, isCOBOL provides the Event-List property, which defines the list of events to be fired. The argument of Event-List is a list of eventClass entries enclosed in parentheses. Each eventClass entry must be enclosed in single or double quotes and is not case-sensitive.

When an event is fired, event-type is set to msg-jb-event and event-data-2 is set to the event name.

Example:

The sample code has been changed, to instruct the calendar to fire the propertyChange event and handle it in the myDateField-Event paragraph.

... working-storage section. ... copy "component.def". ... screen section. ... 03 myDateField     java-bean    clsid           "com.toedter.calendar.JDateChooser"    line            2    col             2    size            30    lines           1.5    object in       objDateField    event-list      ("propertyChange")    event procedure myDateField-Event

The event procedure will look like this:

myDateField-Event.     evaluate event-type     when msg-jb-event          evaluate event-data-2          when COMPONENT-PROPERTYCHANGE               (Imperative statement)          end-evaluate     end-evaluate     .

Some events may return additional information. To retrieve it, the special-names "event source" and "event object" may be defined in the working-storage section of the program.

... configuration section. repository.    class iscobol-java-bean             as "com.iscobol.gui.server.CobolGUIJavaBean"    class java-event-object             as "java.util.EventObject" ... working-storage section. ... 77 eventSource is special-names event source object reference iscobol-java-bean. 77 eventObject is special-names event object object reference java-event-object.  ...

No reference to a specific java-bean is made. Like other special-names, event source and event object are automatically handled by isCOBOL.

eventSource is a reference to the built-in object com.iscobol.gui.server.CobolGUIJavaBean and represents the object that fired the event. It provides a convenient and generic way to interact with object firing events.

eventObject is a reference to the standard java object java.util.EventObject, the class from which all event state objects derive. To handle a specific event fired by a java-bean, the reference to that event object must be used.

Example:

... configuration section. repository.    class iscobol-java-bean             as "com.iscobol.gui.server.CobolGUIJavaBean"    class java-event-object             as "java.util.EventObject"    class property-change-event         as "java.beans.PropertyChangeEvent" ... working-storage section. ... 77 eventSource is special-names event source object reference iscobol-java-bean. 77 eventObject is special-names event object object reference java-event-object.  77 propertyChangeEvent object reference property-change-event.  77 propertyName pic x any length. ... myDateField-Event.     evaluate event-type     when msg-jb-event          evaluate event-data-2          when COMPONENT-PROPERTYCHANGE               set propertyChangeEvent to eventObject as property-change-event               set propertyName to propertyChangeEvent:>getPropertyName               display message "The property " propertyName " has changed."          end-evaluate     end-evaluate     .