The event dispatching thread (EDT) is a background thread used in Java to process events from the Abstract Windowing Toolkit (AWT) graphical user interfaceevent queue. These events are primarily update events that cause user interface components to redraw themselves, or input events from input devices such as the mouse or keyboard. The AWT uses a single-threaded painting model in which all screen updates must be performed from a single thread. The event dispatching thread is the only valid thread to update the visual state of visible user interface components. Updating visible components from other threads is the source of many common bugs in Java programs that use Swing[1].
Other application threads can execute code in the event dispatching thread by defining the code in a object and pass it to the helper class or to the . Two methods of these classes allow:
synchronous code execution ( or )
and asynchronous code execution ( or )
from the EDT.
The method invokeAndWait() should never be called from the event dispatching thread—it will throw an exception. The method or can be called to determine if the current thread is the event dispatching thread.
Another solution for executing code in the EDT is using the worker design pattern. The SwingWorker class, developed by Sun Microsystems, is an implementation of the worker design pattern, and as of Java 6 is part of standard Swing distribution. The open source project Foxtrot provides another synchronous execution solution similar to SwingWorker.
Encyclopedia
top
