action.html

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<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html"><code>AbstractAction</code></a> and then instantiate it.
In your subclass, 
you must implement the <code>actionPerformed</code> method 
to react appropriately 
when the action event occurs.
Here's an example of creating and instantiating
an <code>AbstractAction</code> subclass:

<blockquote><pre>
leftAction = new LeftAction("Go left", anIcon,
             "This is the left button.",
             new Integer(KeyEvent.VK_L));
...
class LeftAction extends AbstractAction {
    public LeftAction(String text, ImageIcon icon,
                      String desc, Integer mnemonic) {
        super(text, icon);
        putValue(SHORT_DESCRIPTION, desc);
        putValue(MNEMONIC_KEY, mnemonic);
    }
    public void actionPerformed(ActionEvent e) {
        displayResult("Action for first button/menu item", e);
    }
}
</pre></blockquote>

<p>
When the action created by the preceding code is attached to a
button and a menu item, the button and menu item display the 
text and icon associated with the action.  The <code>L</code>
character is used for mnemonics on the button and menu item, and
their tool-tip text is set to the <code>SHORT_DESCRIPTION</code>
string followed by a representation of the mnemonic key.
<p>
For example, we have provided a simple example,
<a class="SourceLink" target="_blank" href="examples/ActionDemo.java"><code>ActionDemo.java</code></a>, which defines three actions. Each action is attached to a button
and a menu item.
Thanks to the mnemonic values set for each button's action, the key
sequence <code>Alt-L</code> activates the left button, <code>Alt-M</code>
the middle button, and <code>Alt-R</code> the right button.  The tool tip
for the left button displays <em>This is the left button. Alt-L.</em>
All of this configuration occurs automatically, without the program making
explicit calls to set the mnemonic or tool-tip text.  As we'll show
later, the program <em>does</em> make calls to set the button text, 
but only to avoid using the values already set by the actions.

<p>
<p><center><IMG SRC="../../figures/uiswing/misc/ActionDemo.png" WIDTH="458" HEIGHT="207" ALIGN="BOTTOM" ALT="A snapshot of ActionDemo, which uses actions to coordinate menus and buttons."></center></p>
<blockquote><hr><strong>Try this:</strong>&nbsp;
<ol>
<li> <a href="http://java.sun.com/docs/books/tutorialJWS/uiswing/misc/examples/ActionDemo.jnlp">Run ActionDemo</a> using
<a class="TutorialLink" target="_top" href="../../information/javawebstart.html">Java<sup><font size=-2>TM</font></sup> Web Start</a>.
     Or, to compile and run the example yourself,
     consult the
     <a href="examples/index.html#ActionDemo">example index</a>.
<li> Choose the top item from the left menu (<b>Menu &gt; Go left</b>).
     <br>
     The text area displays some text identifying both
     the event source and
     the action listener that received the event.
<li> Click the leftmost button in the tool bar.
     <br>
     The text area again displays 
     information about the event.
     Note that although the source of the events is different,
     both events were detected by the same action listener:
     the <code>Action</code> object attached to the components.
<li> Choose the top item from the <b>Action State</b> menu.
     <br>
     This disables the "Go left" <code>Action</code> object,
     which in turn disables
     its associated menu item and button.
</ol>
<hr></blockquote>

Here is what the user sees
when the "Go left" action is disabled:
<table border="0">
<tr>
<td>

<p><center><IMG SRC="../../figures/uiswing/misc/ActionDemo-a.png" WIDTH="458" HEIGHT="207" ALIGN="BOTTOM" ALT="A snapshot of ActionDemo when "Go Left" is disabled."></center></p></td><td>

<p><center><IMG SRC="../../figures/uiswing/misc/ActionDemo-b.png" WIDTH="458" HEIGHT="207" ALIGN="BOTTOM" ALT="A snapshot of ActionDemo when "Go Left" is disabled."></center></p></td></tr>
</table>


<p>

Here's the code that disables the "Go left" action:
<blockquote><pre>
boolean selected = ...//<em>true if the action should be enabled;</em>
                      //<em>false, otherwise</em>
leftAction.setEnabled(selected);
</pre></blockquote>

After you create components using an <code>Action</code>,
you might well need to customize them.
For example, you might want to customize the
appearance of one of the components
by adding or deleting the icon or text.
For example, 

<a class="SourceLink" target="_blank" href="examples/ActionDemo.java"><code>ActionDemo.java</code></a>
has no icons in its menus, and no text in its buttons.
Here's the code that accomplishes this:

<blockquote><pre>
menuItem = new JMenuItem();
menuItem.setAction(leftAction);
menuItem.setIcon(null); //arbitrarily chose not to use icon in menu
...
button = new JButton();
button.setAction(leftAction);
button.setText(""); //an icon-only button
</pre></blockquote>

<p>We chose to create an icon-only button and
a text-only menu item from the same action by setting
the icon property to <code>null</code> and the text
to an empty string.
However, if a property of the <code>Action</code> changes, the
widget may try to reset the icon and text from the
<code>Action</code> again.

</blockquote>
<h3>
<a name="api">The Action API</a>
</h3>
<blockquote>
The following tables list the commonly used
<code>Action</code> constructors and methods.
The API for using <code>Action</code> objects
falls into three categories:

<ul>
<li><a href="#actioncomponents">Components that Support set/getAction</a>
<li><a href="#actionapi">Creating and Using an AbstractAction</a>
<li><a href="#properties">Action Properties</a>
</ul>

<p>
<table border=1>
<caption><a name="actioncomponents">Components that Support set/getAction</a></caption>
<tr>
<th align=left>Class</th>
<th align=left>Purpose</th>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractButton.html#setAction(javax.swing.Action)">AbstractButton</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#setAction(javax.swing.Action)">JComboBox</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextField.html#setAction(javax.swing.Action)">JTextField</a></td>
<td>
As of release 1.3, these components and their
subclasses may have an action directly assigned
to them via <code>setAction</code>.
For further information about components that are often
associated with actions, see the sections on
<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>.
For details on which properties
each component takes from the <code>Action</code>,
see the API documentation for the relevant class's
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JMenuItem.html#configurePropertiesFromAction(javax.swing.Action)"><code>configurePropertiesFromAction</code></a> method.

</tr>
</tr>
</table>


<p>
<table border=1> 
<caption><a name="actionapi">Creating and Using an AbstractAction</a></caption>
<tr>
<th align=left>Constructor or Method</th>
<th align=left>Purpose</th>
</tr>
 
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#AbstractAction()">AbstractAction()</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#AbstractAction(java.lang.String)">AbstractAction(String)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#AbstractAction(java.lang.String, javax.swing.Icon)">AbstractAction(String, Icon)</a></td>
<td>Create an <code>Action</code> object.
    Through arguments,
    you can specify the text and icon
    to be used in the components that the action controls.</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#setEnabled(boolean)">void setEnabled(boolean)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#isEnabled()">boolean isEnabled()</a></td>
<td>Set or get whether the components the action controls are enabled.
    Invoking <code>setEnabled(false)</code>
    disables all the components that the action controls.
    Similarly, invoking <code>setEnabled(true)</code>
    enables the action's components.</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#putValue(java.lang.String, java.lang.Object)">void putValue(String, Object)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html#getValue(java.lang.String)">Object getValue(String)</a></td>
<td>Set or get an object associated with a specified key.
    Used for setting and getting properties associated
    with an action.
</td>
</tr>

</table>

<p>
<p align=center><a name="properties">Action Properties</a>
<p>This table defines the properties that can be set on an
action.  The second column lists which components automatically
use the properties (and what method is specifically called).
For example,
setting the <code>ACCELERATOR_KEY</code> on an action that
is then attached to a menu item, means that
<code>JMenuItem.setAccelerator(KeyStroke)</code>
is called automatically.
<p>
<table border=1> 
<tr>
<th align=left>Property</th>
<th align=left>Auto-Applied to: <br>Class <br><em>(Method Called)</em></th>
<th align=left>Purpose</th>
</tr>
 
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#ACCELERATOR_KEY">ACCELERATOR_KEY</a></td>
<td><code>JMenuItem</code>
    <br>(<em>setAccelerator</em>)
</td>
<td>The <code>KeyStroke</code> to be used as the accelerator for
    the action.
    For a discussion of accelerators versus mnemonics, see
<a class="TutorialLink" target="_top" href="../components/menu.html#mnemonic">Enabling Keyboard Operation.</a>    Introduced in 1.3.
</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#ACTION_COMMAND_KEY">ACTION_COMMAND_KEY</a></td>
<td><code>AbstractButton</code>, <code>JCheckBox</code>,
    <code>JRadioButton</code>
    <br>(<em>setActionCommand</em>)
</td>
<td>The command string associated with the
    <code>ActionEvent</code>.
</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#LONG_DESCRIPTION">LONG_DESCRIPTION</a></td>
<td>None
</td>
<td>The longer description for the action.
    Can be used for context-sensitive help.
</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#MNEMONIC_KEY">MNEMONIC_KEY</a></td>
<td><code>AbstractButton</code>, <code>JMenuItem</code>,
    <code>JCheckBox</code>, <code>JRadioButton</code>
    <br>(<em>setMnemonic</em>)
</td>
<td>The mnemonic for the action.
    For a discussion of accelerators versus mnemonics, see
<a class="TutorialLink" target="_top" href="../components/menu.html#mnemonic">Enabling Keyboard Operation.</a>    Introduced in 1.3. 
</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#NAME">NAME</a></td>
<td><code>AbstractButton</code>, <code>JMenuItem</code>,
    <code>JCheckBox</code>, <code>JRadioButton</code>
    <br>(<em>setText</em>)
</td>
<td>The name of the action.
    You can set this property when creating the action using
    the <code>AbstractAction(String)</code> or 
    <code>AbstractAction(String, Icon)</code> constructors.
</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#SHORT_DESCRIPTION">SHORT_DESCRIPTION</a></td>
<td><code>AbstractButton</code>,
    <code>JCheckBox</code>, <code>JRadioButton</code>
    <br>(<em>setToolTipText</em>)
</td>
<td>The short description of the action.
</td>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html#SMALL_ICON">SMALL_ICON</a></td>
<td><code>AbstractButton</code>, <code>JMenuItem</code>
    <br>(<em>setIcon</em>)
</td>
<td>The icon for the action used in the tool bar or on
    a button.
    You can set this property when creating the action using
    the <code>AbstractAction(name, icon)</code> constructor.
</td>
</tr>
</table>


</blockquote>
<h3>
<a name="eg">Examples that Use Actions</a>
</h3>
<blockquote>
The following examples
use <code>Action</code> objects.
<p>
<table>
<tr>
<th align=left> Example</th>
<th align=left> Where Described</th>
<th align=left> Notes</th>
</tr>

<tr>
<td> <a href="examples/index.html#ActionDemo"><code>ActionDemo</code></a></td>
<td> This section</td>
<td> Uses actions to bind buttons and menu items to the same function.</td>
</tr>

<tr>
<td> <a href="../components/examples/index.html#TextComponentDemo">
     <code>TextComponentDemo</code></a></td>
<td> 
<a class="TutorialLink" target="_top" href="../components/generaltext.html">Text Component Features</a></td>
<td> Uses text actions to create menu items
     for text editing commands, such as cut, copy, and paste,
     and to bind key strokes to caret movement.
     Also implements custom <code>AbstractAction</code> subclasses
     to implement undo and redo.
     The text action discussion begins in
     <a href="../components/generaltext.html#editorkits">Concepts:
     About Editor Kits</a>.</td>
</tr>

</table>


        </blockquote>
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