action.html
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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> Using Other Swing Features </div> <div id=LeftBar class=LeftBar_shown> <div id=Contents> <div class="linkLESSON"><a href="index.html">Using Other Swing Features</a></div><div class="nolinkAHEAD">How to Use Actions</div><div class="linkAHEAD"><a href="timer.html">How to Use Swing Timers</a></div><div class="linkAHEAD"><a href="access.html">How to Support Assistive Technologies</a></div><div class="linkAHEAD"><a href="focus.html">How to Use the Focus Subsystem</a></div><div class="linkAHEAD"><a href="keybinding.html">How to Use Key Bindings</a></div><div class="linkAHEAD"><a href="problems.html">Solving Common Problems Using Other Swing Features</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>Using Other Swing Features</a> </span> <div class=NavBit> <a target=_top href=index.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=timer.html>Next »</a> </div> <div id=PageTitle>How to Use Actions</div> <blockquote><p>If you have two or more componentsthat perform the same function,consider using an<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html"><code>Action</code></a> object to implement the function.An <code>Action</code> object is an<a class="TutorialLink" target="_top" href="../events/actionlistener.html">action listener</a> that provides not only action-event handling,but also centralized handling of the stateof action-event-firing components such as <a class="TutorialLink" target="_top" href="../components/toolbar.html">tool bar buttons</a>,<a class="TutorialLink" target="_top" href="../components/menu.html">menu items</a>, <a class="TutorialLink" target="_top" href="../components/button.html">common buttons</a>, and<a class="TutorialLink" target="_top" href="../components/textfield.html">text fields</a>.The state that an action can handle includestext, icon, mnemonic, and enabled status.<blockquote><hr><strong>Note:</strong> One of our Swing engineers, Scott Violet, has a blog that discusses<a class="OutsideLink" target="_blank" href="http://weblogs.java.net/blog/zixle/archive/2005/11/the_usefulness.html">The Usefulness of Actions</a> and mentions some of the new <code>Action</code> properties comingin release 6.<hr></blockquote><p>You typically attach an action to a componentusing the <code>setAction</code> method.Here's what happens when <code>setAction</code> is invokedon a component:<ul><li> The component's state is updated to match the state of the <code>Action</code>. For example, if the <code>Action</code>'s text and icon values were set, the component's text and icon are set to those values.<li> The <code>Action</code> object is registered as an action listener on the component.<li> If the state of the <code>Action</code> changes, the component's state is updated to match the <code>Action</code>. For example, if you change the enabled status of the action, all components it's attached to change their enabled states to match the action.</ul>Here's an example of creating a tool-bar button and menu itemthat perform the same function:<blockquote><pre>Action leftAction = new LeftAction(); <em>//LeftAction code is shown later</em>...button = new JButton(leftAction)...menuItem = new JMenuItem(leftAction);</pre></blockquote><p><blockquote><hr><strong>Version Note:</strong> Prior to 1.3,the only way for a button or menu itemto get the full benefit of using an <code>Action</code>was to create the component using the<code>add(Action)</code> method of<code>JToolBar</code>,<code>JMenu</code>, or <code>JPopupMenu</code>.This was because the pre-1.3 releaseshave no API except <code>addActionListener(ActionListener)</code>to connect an <code>Action</code> to an already existing component.Although you coulduse <code>addActionListener</code>to add an <code>Action</code> object as an action listener to any button,for example,the button wouldn't be notified when the action was disabled.<hr></blockquote><p>To create an <code>Action</code> object,you generally create a subclass of⌨️ 快捷键说明
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