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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 ...
In Windows, a message is equated to an event created and imposed upon the operating system. An event can be user interaction, network traffic, system processing, timer activity, inter-process communication, among others. For non-interactive, I/O only events, Windows has I/O completion ports. I/O completion port loops run separately from the ...
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.
Even when synchronous handling appears to block execution, the underlying mechanism in many systems is still asynchronous, managed by the event loop. [ 1 ] [ 2 ] Events can be implemented through various mechanisms such as callbacks, message objects, signals, or interrupts, and events themselves are distinct from the implementation mechanisms used.
Remote Method Invocation (Java RMI) and Java Native Interface (JNI) are such examples. [4] [5] In addition, J++ implemented other extensions that were not part of Sun's Java implementation. The inclusion of callbacks and delegates for event handling further defined J++ as a completely different language merely based on an already existing ...
In the traditional model, [21] event handlers can be added or removed by scripts. Like the inline model, each event can only have one event handler registered. The event is added by assigning the handler name to the event property of the element object. To remove an event handler, simply set the property to null:
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.
For example, code can be inserted into the form resize event handler to reposition a control so that it remains centered on the form, expands to fill up the form, etc. By inserting code into the event handler for a keypress in a text box, the program can automatically translate the case of the text being entered, or even prevent certain ...