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© IBM Corporation 2013
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Defining and Registering Events in Object Oriented ABAP
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© IBM Corporation 2013Developing User Interfaces with Web Dynpro for ABAP | Jan-2011 2
Agenda
Define and trigger events
Register and handle events
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Unit Objectives
Define and trigger events
Handle events
Register and deregister events
Receive a reference from the sender
Explain the conceptual differences between methods and events
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Overview
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Characteristics and Uses
Looser linkage than for a method call
Different communication model
Trigger does not know the user
Important for GUI implementation
Conformity to other object models COM
ActiveX Controls
OpenDoc
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Triggering and Handling Events: Overview
Triggering events Class defines event (EVENTS, CLASS-EVENTS)
Object or class triggers event (RAISE EVENT)
Handling events Event handler class defines and implements event handler method
([CLASS-]METHODS... FOR EVENT ... OF ...)
Event handler object” or handler class registers itself to specific object/class events at runtime (SET HANDLER)
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Defining and Triggering Events: Syntax
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Handling and Registering Events
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Handling Events: Syntax
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Registering for an Event: Syntax
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Deregistration and the Implicit Reference SENDER
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Registration/Deregistration: Handler Table
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Defining View Layout
Event handling is sequential.
Sequence in which event handler methods are called is not defined.
As far as the Garbage Collector is concerned, registration has the same effect as a reference to the object registered.
Registered objects are never deleted.
Immediate effects of SET HANDLER on event handler
methods:
Newly registered event handlers are also executed.
Deregistered handlers may already have been executed.
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Events and Visibility
The visibility of an event establishes authorization for event handling.
The visibility in an event handler method establishes authorization for SET-HANDLER statements.
An event handler method must have either the same or more restricted visibility than the event it refers to :
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Events: Unit summary
You are now able to: Define and trigger events
Handle events
Register and deregister events
Explain the conceptual differences between
methods and events
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Hands-on Exercise 8
Objectives: Define and trigger events
Handle events
Register for events