dispatch.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"><html> <head> <title>The Event Dispatch Thread (The Java™ Tutorials > Creating a GUI with JFC/Swing > Concurrency in Swing)</title><style type="text/css"> .FigureCaption { margin-left: 1in; margin-right: 1in; font-family: sans-serif; font-size: smaller; text-align: justify; } #TopBar_bl { background: url(../../images/java_bar_bl.gif) 0 100% no-repeat; width: 100%; height: 60px; } #TopBar_br { background: url(../../images/java_bar_br.gif) 100% 100% no-repeat; width: 100%; height: 60px; } #TopBar_tl { background: url(../../images/java_bar_tl.gif) 0 0 no-repeat; width: 100%; height: 60px; } #TopBar_tr { background: url(../../images/java_bar_tr.gif) 100% 0 no-repeat; width: 100%; height: 60px; } #TopBar { background: #35556B url(../../images/java_bar.gif); margin: 10px 10px 0 10px; height:60px; min-width:700px; color: white; font-family: sans-serif; font-weight: bold; } @media print { #BreadCrumbs, #Download { display: none; } } #TopBar_right { line-height: 14px; 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var main = document.getElementById("MainFlow"); var toggle = document.getElementById("ToggleLeft"); if (b) { contents.className = "LeftBar_shown"; main.className = "MainFlow_indented"; toggle.innerHTML = "Hide the TOC"; document.cookie = 'tutorial_showLeftBar=yes; path=/'; } else { contents.className = "LeftBar_hidden"; main.className = "MainFlow_wide"; toggle.innerHTML = "Show the TOC"; document.cookie = 'tutorial_showLeftBar=no; path=/'; } } function toggleLeft() { showLeft(document.getElementById("LeftBar").className == "LeftBar_hidden"); document.getElementById("ToggleLeft").blur(); } function load() { showLeft(leftBar()); document.getElementById("ToggleLeft").style.display="inline"; } </script> </head><body onload="load()"> <div id=TopBar> <div id=TopBar_tr> <div id=TopBar_tl> <div id=TopBar_br> <div id=TopBar_bl> <div id=TopBar_right> <a target="_blank" href="http://java.sun.com/javase/6/download.jsp">Download the JDK</a> <br> <a href="../../search.html" target="_blank">Search the Tutorials</a> <br> <a href="javascript:toggleLeft()" id="ToggleLeft">Hide the TOC</a> </div> </div> </div> </div> </div> </div> <div class=PrintHeaders> <b>Trail:</b> Creating a GUI with JFC/Swing <br><b>Lesson:</b> Concurrency in Swing </div> <div id=LeftBar class=LeftBar_shown> <div id=Contents> <div class="linkLESSON"><a href="index.html">Concurrency in Swing</a></div><div class="linkAHEAD"><a href="initial.html">Initial Threads</a></div><div class="nolinkAHEAD">The Event Dispatch Thread</div><div class="linkAHEAD"><a href="worker.html">Worker Threads and SwingWorker</a></div><div class="linkBHEAD"><a href="simple.html">Simple Background Tasks</a></div><div class="linkBHEAD"><a href="interim.html">Tasks that Have Interim Results</a></div><div class="linkBHEAD"><a href="cancel.html">Canceling Background Tasks</a></div><div class="linkBHEAD"><a href="bound.html">Bound Properties and Status Methods</a></div></div> </div> <div id=MainFlow class=MainFlow_indented> <span id=BreadCrumbs> <a href=../../index.html target=_top>Home Page</a> > <a href=../index.html target=_top>Creating a GUI with JFC/Swing</a> > <a href=index.html target=_top>Concurrency in Swing</a> </span> <div class=NavBit> <a target=_top href=initial.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=worker.html>Next »</a> </div> <div id=PageTitle>The Event Dispatch Thread</div> <blockquote>Swing event handling code runs on a special thread known as theevent dispatch thread. Most code that invokes Swing methodsalso runs on this thread.This is necessary because most Swingobject methods are not "thread safe": invoking them from multiplethreads risks<a class="TutorialLink" target="_top" href="../../essential/concurrency/interfere.html">thread interference</a>or<a class="TutorialLink" target="_top" href="../../essential/concurrency/memconsist.html">memory consistency errors</a>.Some Swing component methods are labelled "thread safe" in the APIspecification; these can be safely invoked from any thread. All otherSwing component methods must be invoked from the eventdispatch thread. Programs that ignore this rule may functioncorrectly most of the time, but are subject to unpredictable errorsthat are difficult to reproduce.<blockquote><hr><strong>A note on thread safety:</strong> It may seem strange that such an important part of the Java platformis not thread safe. It turns out that any attempt to create athread-safe GUI library faces some fundamental problems. For more onthis issue, see the following entry in Graham Hamilton's blog:<a class="OutsideLink" target="_blank" href="http://weblogs.java.net/blog/kgh/archive/2004/10/multithreaded_t.html">MultiThreaded toolkits: A failed dream?</a><hr></blockquote>It's useful to think of the code running on the event dispatch threadas a series of short tasks. Most tasks are invocations ofevent-handling methods, such as<code>ActionListener.actionPerformed</code>. Other tasks can bescheduled by application code, using <code>invokeLater</code> or<code>invokeAndWait</code>. Tasks on the event dispatch thread mustfinish quickly; if they don't, unhandled events back up and the userinterface becomes unresponsive.<p>If you need to determine whether your code is running on the eventdispatch thread, invoke<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SwingUtilities.html#isEventDispatchThread()"><code>javax.swing.SwingUtilities.isEventDispatchThread</code></a>. </blockquote> <div class=NavBit> <a target=_top href=initial.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=worker.html>Next »</a> </div> </div> <div id=Footer><div id=TagNotes> Problems with the examples? Try <a target="_blank" href=../../information/run-examples.html>Compiling and Running the Examples: FAQs</a>. <br> Complaints? Compliments? Suggestions? <a target="_blank" href="http://developer.sun.com/contact/tutorial_feedback.jsp">Give us your feedback</a>.<br><br> <a target="_blank" href="../../information/copyright.html">Copyright</a> 1995-2006 Sun Microsystems, Inc. All rights reserved. <span id=Download></span></div> </div> <div class=PrintHeaders> <b>Previous page:</b> Initial Threads <br><b>Next page:</b> Worker Threads and SwingWorker </div> </body></html> ⌨️ 快捷键说明
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