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Below is an example written in Java that takes keyboard input and handles each input line as an event. When a string is supplied from System.in , the method notifyObservers() is then called in order to notify all observers of the event's occurrence, in the form of an invocation of their update methods.
The actual logic is contained in event-handler routines. These routines handle the events to which the main program will respond. For example, a single left-button mouse-click on a command button in a GUI program may trigger a routine that will open another window, save data to a database or exit the application.
The event dispatching thread (EDT) is a background thread used in Java to process events from the Abstract Window Toolkit (AWT) graphical user interface event queue. It is an example of the generic concept of event-driven programming, that is popular in many other contexts than Java, for example, web browsers, or web servers. The events are ...
Mouse events. [3] [4] Keyboard events. HTML frame/object events. HTML form events. User interface events. Mutation events (notification of any changes to the structure of a document). Progress events [5] (used by XMLHttpRequest and File API [6]). Note that the event classification above is not exactly the same as W3C's classification.
Microsoft Windows for example, allows users to insert hooks that can be used to process or modify system events and application events for dialogs, scrollbars, and menus as well as other items. It also allows a hook to insert, remove, process or modify keyboard and mouse events.
Event propagation models, such as bubbling, capturing, and pub/sub, define how events are distributed and handled within a system. Other key aspects include event loops, event queueing and prioritization, event sourcing, and complex event processing patterns. These mechanisms contribute to the flexibility and scalability of event-driven systems.
A sample UML class and sequence diagram for the Command design pattern. [3]In the above UML class diagram, the Invoker class doesn't implement a request directly. Instead, Invoker refers to the Command interface to perform a request (command.execute()), which makes the Invoker independent of how the request is performed.
C# multicast-delegates are used with events. Events provide support for event-driven programming and are an implementation of the observer pattern. To support this there is a specific syntax to define events in classes, and operators to register, unregister or combine event handlers. See here for information about how events are implemented in ...