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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"><html> <head> <title>Bound Properties and Status Methods (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 <br><b>Section:</b> Worker Threads and SwingWorker </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="linkAHEAD"><a href="dispatch.html">The Event Dispatch Thread</a></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="nolinkBHEAD">Bound Properties and Status Methods</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=cancel.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=../QandE/questions-concurrency.html>Next »</a> </div> <div id=PageTitle>Bound Properties and Status Methods</div> <blockquote><code>SwingWorker</code> supports<a class="TutorialLink" target="_top" href="../../javabeans/properties/bound.html">bound properties</a>, which are useful for communicating with other threads. Two boundproperties are predefined: <code>progress</code> and<code>state</code>. As with all bound properties,<code>progress</code> and <code>state</code> can be used to triggerevent-handling tasks on the event dispatch thread.<p>By implementing a property change listener, a program can trackchanges to <code>progress</code>, <code>state</code>, and other boundproperties. For more information, refer to<a class="TutorialLink" target="_top" href="../events/propertychangelistener.html">How to Write a Property Change Listener</a>in<a class="TutorialLink" target="_top" href="../events/index.html">Writing Event Listeners</a>.<h3>The <code>progress</code> Bound Variable</h3>The <code>progress</code> bound variable is an <code>int</code> valuethat can range from 0 to 100. It has a predefined setter method (the protected<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SwingWorker.html#setProgress()"><code>SwingWorker.setProgress</code></a>)and a predefined getter method (the public<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SwingWorker.html#getProgress(int)"><code>SwingWorker.getProgress</code></a>).<p>The<a class="SourceLink" target="_blank" href="../components/examples/ProgressBarDemo.java"><code><code>ProgressBarDemo</code></code></a>example uses <code>progress</code> to update a<code>ProgressBar</code> control from a background task. For adetailed discussion of this example, refer to<a class="TutorialLink" target="_top" href="../components/progress.html">How to Use Progress Bars</a>in<a class="TutorialLink" target="_top" href="../components/index.html">Using Swing Components</a>.<h3>The <code>state</code> Bound Variable</h3>The <code>state</code> bound variable indicates where the<code>SwingWorker</code> object is in its lifecycle.The bound variable contains an enumeration value of type<code>SwingWorker.StateValue</code>. Possible values are:<dl> <dt><code>PENDING</code> <dd>The state during the period from the construction of the object until just before <code>doInBackground</code> is invoked. <dt><code>STARTED</code> <dd>The state during the period from shortly before <code>doInBackground</code> is invoked until shortly before <code>done</code> is invoked. <dt<code>DONE</code> <dd>The state for the remainder of the existence of the object.</dl>The current value of the <code>state</code> bound variable is returned by<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SwingWorker.html#getState()"><code>SwingWorker.getState</code></a>. <h3>Status Methods</h3>Two methods, part of the <code>Future</code> interface, also report onthe status of the background task. As we saw in<a class="TutorialLink" target="_top" href="cancel.html">Canceling Background Tasks</a>, <code>isCancelled</code> returns <code>true</code> if the task has beencanceled. In addition, <code>isDone</code> returns <code>true</code> ifthe task has finished, either normally, or by being cancelled. </blockquote> <div class=NavBit> <a target=_top href=cancel.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=../QandE/questions-concurrency.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> Canceling Background Tasks <br><b>Next page:</b> Questions and Exercises: Concurrency in Swing </div> </body></html> ⌨️ 快捷键说明
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