Docstoc

Event Driven Programming Event Driven Programming Key Features Event Driven Programs

Document Sample
Event Driven Programming Event Driven Programming Key Features Event Driven Programs Powered By Docstoc
					Event Driven Programming
               Key Features
Event Driven Programs

Typically used for most modern day
 software applications examples include:
 word processing, spreadsheets, drawing
 packages etc.

Usually used for GUIs where many types
 of events are generated i.e. clicking on a
 button or another object
Key features
 Event Handlers
 Trigger Functions
 Events
 Event Loops
 Forms
 Flexibility
 Service oriented
 Suitability for GUIs
 Simplicity of programming
 Time Driven
Event Handlers

VB.Net uses subroutines for event
 handling, with the name of the object
 followed by the name of the event – see
 below:               Event



 Event
 Handler
Trigger functions
 These are used along with the object’s name to determine with event handler to run

 Every object has a range of trigger functions, one for each possible event that can
  happen to it. For example, txtText could have an event handler for the following
  triggers: GotFocus, TextChanged etc...
 Temporal triggers mean triggers set off by duration of time
 State triggers are when the current situation causes a certain set of procedures to run

 What is the trigger here??
Event Loops
 Event Driven Programs have event loops built into the
  environment. The loops keep testing the interface to
  detect whether anything has happened, such as clicking
  on a button or typing into a textbox etc.

 Event Loops are also known as event listeners
Flexibility

Programmers have enormous control over
 where to place code and how to start it.

Every object has a good choice of events
 that a program can respond to. These
 events give an excellent level of control
 over exactly what the program will respond
 to when the user does something
Service Oriented
 A lot of networked applications use service oriented
  techniques so that different applications can reuse code
  components.

 Service oriented applications separate the service
  implementation from the program interface that uses the
  service.
 An example is a request from a database.

 XML (Extensible Markup Language) is commonly used
  for interfacing with such service oriented architectures.
Time Driven
Time driven programming is often used in
 real time, where code execution is
 controlled by the computer clock.

A program is divided into a set of tasks
 that need to be regularly activated. The
 activation pattern us stored into a dispatch
 table, where rules are used to schedule
 the tasks.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:303
posted:10/27/2011
language:English
pages:9