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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>CardLayout</title><link rel="stylesheet" href="core.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.74.0"/></head><body><div class="sect1" title="CardLayout"><div class="titlepage"><div><div><h1 class="title"><a id="learnjava3-CHP-19-SECT-5"/>CardLayout</h1></div></div></div><p><a id="idx11046" class="indexterm"/> <a id="idx11066" class="indexterm"/> <code class="literal">CardLayout</code> is a special
layout manager for creating the effect of a “stack” of components. Instead
of arranging all of the container’s components, it displays only one at a
time. You might use this kind of layout to implement a custom-tabbed panel
of some kind. In fact, there’s probably little reason to use this layout
given the Swing <code class="literal">JTabbedPane</code> component
described in <a class="xref" href="ch17.html" title="Chapter 17. Using Swing Components">Chapter 17</a>. We include it here
mainly for completeness.</p><p>To add a component to a <code class="literal">CardLayout</code>, use a two-argument version of the
container’s <code class="literal">add()</code> method; the extra
argument is an arbitrary string that serves as the card’s name:</p><a id="I_19_tt1117"/><pre class="programlisting"> <code class="n">add</code><code class="o">(</code><code class="s">"netconfigscreen"</code><code class="o">,</code> <code class="n">myComponent</code><code class="o">);</code></pre><p>To bring a particular card to the top of the stack, call the
<code class="literal">CardLayout</code>’s <code class="literal">show()</code> method with two arguments: the parent
<code class="literal">Container</code> and the name of the card you
want to show. There are also methods—<code class="literal">first()</code>, <code class="literal">last()</code>, <code class="literal">next()</code>, and <code class="literal">previous()</code>—for working with the stack of cards.
These are all <code class="literal">CardLayout</code> instance
methods. To invoke them, you need a reference to the <code class="literal">CardLayout</code> object itself, not to the container
it manages. Each method takes a single argument: the parent <code class="literal">Container</code>. Here’s an example:</p><a id="I_19_tt1118"/><pre class="programlisting"> <code class="c1">//file: Card.java</code>
<code class="kn">import</code> <code class="nn">java.awt.*</code><code class="o">;</code>
<code class="kn">import</code> <code class="nn">java.awt.event.*</code><code class="o">;</code>
<code class="kn">import</code> <code class="nn">javax.swing.*</code><code class="o">;</code>
<code class="kd">public</code> <code class="kd">class</code> <code class="nc">Card</code> <code class="kd">extends</code> <code class="n">JPanel</code> <code class="o">{</code>
<code class="n">CardLayout</code> <code class="n">cards</code> <code class="o">=</code> <code class="k">new</code> <code class="n">CardLayout</code><code class="o">();</code>
<code class="kd">public</code> <code class="nf">Card</code><code class="o">()</code> <code class="o">{</code>
<code class="n">setLayout</code><code class="o">(</code><code class="n">cards</code><code class="o">);</code>
<code class="n">ActionListener</code> <code class="n">listener</code> <code class="o">=</code> <code class="k">new</code> <code class="n">ActionListener</code><code class="o">()</code> <code class="o">{</code>
<code class="kd">public</code> <code class="kt">void</code> <code class="nf">actionPerformed</code><code class="o">(</code><code class="n">ActionEvent</code> <code class="n">e</code><code class="o">)</code> <code class="o">{</code>
<code class="n">cards</code><code class="o">.</code><code class="na">next</code><code class="o">(</code><code class="n">Card</code><code class="o">.</code><code class="na">this</code><code class="o">);</code>
<code class="o">}</code>
<code class="o">};</code>
<code class="n">JButton</code> <code class="n">button</code><code class="o">;</code>
<code class="n">button</code> <code class="o">=</code> <code class="k">new</code> <code class="n">JButton</code><code class="o">(</code><code class="s">"one"</code><code class="o">);</code>
<code class="n">button</code><code class="o">.</code><code class="na">addActionListener</code><code class="o">(</code><code class="n">listener</code><code class="o">);</code>
<code class="n">add</code><code class="o">(</code><code class="n">button</code><code class="o">,</code> <code class="s">"one"</code><code class="o">);</code>
<code class="n">button</code> <code class="o">=</code> <code class="k">new</code> <code class="n">JButton</code><code class="o">(</code><code class="s">"two"</code><code class="o">);</code>
<code class="n">button</code><code class="o">.</code><code class="na">addActionListener</code><code class="o">(</code><code class="n">listener</code><code class="o">);</code>
<code class="n">add</code><code class="o">(</code><code class="n">button</code><code class="o">,</code> <code class="s">"two"</code><code class="o">);</code>
<code class="n">button</code> <code class="o">=</code> <code class="k">new</code> <code class="n">JButton</code><code class="o">(</code><code class="s">"three"</code><code class="o">);</code>
<code class="n">button</code><code class="o">.</code><code class="na">addActionListener</code><code class="o">(</code><code class="n">listener</code><code class="o">);</code>
<code class="n">add</code><code class="o">(</code><code class="n">button</code><code class="o">,</code> <code class="s">"three"</code><code class="o">);</code>
<code class="o">}</code>
<code class="kd">public</code> <code class="kd">static</code> <code class="kt">void</code> <code class="nf">main</code><code class="o">(</code><code class="n">String</code><code class="o">[]</code> <code class="n">args</code><code class="o">)</code> <code class="o">{</code>
<code class="n">JFrame</code> <code class="n">frame</code> <code class="o">=</code> <code class="k">new</code> <code class="n">JFrame</code><code class="o">(</code><code class="s">"Card"</code><code class="o">);</code>
<code class="n">frame</code><code class="o">.</code><code class="na">setDefaultCloseOperation</code><code class="o">(</code> <code class="n">JFrame</code><code class="o">.</code><code class="na">EXIT_ON_CLOSE</code> <code class="o">);</code>
<code class="n">frame</code><code class="o">.</code><code class="na">setSize</code><code class="o">(</code><code class="mi">200</code><code class="o">,</code> <code class="mi">200</code><code class="o">);</code>
<code class="n">frame</code><code class="o">.</code><code class="na">setLocation</code><code class="o">(</code><code class="mi">200</code><code class="o">,</code> <code class="mi">200</code><code class="o">);</code>
<code class="n">frame</code><code class="o">.</code><code class="na">setContentPane</code><code class="o">(</code><code class="k">new</code> <code class="n">Card</code><code class="o">());</code>
<code class="n">frame</code><code class="o">.</code><code class="na">setVisible</code><code class="o">(</code><code class="kc">true</code><code class="o">);</code>
<code class="o">}</code>
<code class="o">}</code></pre><p>We add three buttons to the layout and cycle through them as they
are pressed. An anonymous inner class serves as an action listener for
each button; it simply calls <code class="literal">CardLayout</code>’s <code class="literal">next()</code> method whenever a button is pressed.
<code class="literal">Card.this</code> refers to the <code class="literal">Card</code> object, which is the container in this
case. In a more realistic example, we would build a group of panels, each
of which might implement some part of a complex user interface and add
those panels to the layout. Each panel would have its own layout manager.
The panels would be resized to fill the entire area available (i.e., the
area of the <code class="literal">Container</code> they are in), and
their individual layout managers would arrange their internal components.<a id="I_indexterm19_id806212" class="indexterm"/><a id="I_indexterm19_id806220" class="indexterm"/></p></div></body></html>