colorchooser.html

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            <div id=PageTitle>How to Use Color Choosers</div>
            <blockquote>
Use the
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JColorChooser.html"><code>JColorChooser</code></a> class to provide users with a palette of colors to choose from.
A color chooser is a component that you can place
anywhere within your program's GUI.
The <code>JColorChooser</code> API also makes it easy
to bring up a <a href="dialog.html">dialog</a>
(modal or not) that contains a color chooser.

<p>
Here's a picture
of an application that uses a color chooser to set
the text color in a banner:

<p><center><IMG SRC="../../figures/uiswing/components/ColorChooserDemoMetal.png" WIDTH="447" HEIGHT="493" ALIGN="BOTTOM" ALT="A snapshot of ColorChooserDemo, which contains a standard color chooser."></center></p>
<font color=red>
[PENDING: Please add call-outs to various parts of the color chooser:
<ul>
<li> color chooser (everything inside and including the "Choose Text Color"
     border)
<li> preview panel (everything inside and including the "Preview" border)
<li> chooser panel (everything inside but NOT including the tabbed pane)]
</ul>
</font>

<p>
You can 
<a href="http://java.sun.com/docs/books/tutorialJWS/uiswing/components/examples/ColorChooserDemo.jnlp">run&nbsp;ColorChooserDemo</a> (it requires release 6)
using 
<a class="TutorialLink" target="_top" href="../../information/javawebstart.html">Java<sup><font size=-2>TM</font></sup> Web Start</a>.  The source code for the program is in

<a class="SourceLink" target="_blank" href="examples/ColorChooserDemo.java"><code>ColorChooserDemo.java</code></a>.

<p>
The color chooser consists of everything within the
box labeled <strong>Choose Text Color</strong>.
This is what a standard color chooser looks like
in the Java Look & Feel.
It contains two parts, a tabbed pane and a preview panel.
The three tabs in the tabbed pane
select <em>chooser panels</em>.
The <em>preview panel</em>
below the tabbed pane
displays the currently selected color.
<p>
Here's the code from the example that creates
a <code>JColorChooser</code> instance
and adds it to a container:

<blockquote><pre>
public class ColorChooserDemo extends JPanel ... {
    public ColorChooserDemo() {
        super(new BorderLayout());
        banner = new JLabel("Welcome to the Tutorial Zone!",
                            JLabel.CENTER);
        banner.setForeground(Color.yellow);
        . . .
        tcc = new JColorChooser(banner.getForeground());
        . . .
        add(tcc, BorderLayout.PAGE_END);
    }
</pre></blockquote>

The <code>JColorChooser</code> constructor in the previous code snippet
takes a <code>Color</code> argument,
which specifies the chooser's initially selected color.
If you don't specify the initial color,
then the color chooser displays
<code>Color.white</code>.
See the 
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/java/awt/Color.html"><code>Color</code> API documentation</a> for a list of color constants you can use.

<p>
<a name="changelistener">
A color chooser uses an instance of
</a>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/colorchooser/ColorSelectionModel.html"><code>ColorSelectionModel</code></a> to contain and manage the current selection.
The color selection model fires a change event
whenever the user changes the color in the color chooser.
The example program registers a change listener with the
color selection model so that it can update the
banner at the top of the window.
The following code registers and implements the change listener:
<blockquote><pre>
tcc.getSelectionModel().addChangeListener(this);
. . .
public void stateChanged(ChangeEvent e) {
    Color newColor = tcc.getColor();
    banner.setForeground(newColor);
}
</pre></blockquote>
See
<a href="../events/changelistener.html">
How to Write a Change Listener</a>
for general information about change listeners and change events.
<p>
A basic color chooser,
like the one used in the example program,
is sufficient for many programs.
However,
the color chooser API allows you to customize a color chooser
by providing it with a preview panel of your own design,
by adding your own chooser panels to it, or
by removing existing chooser panels from the color chooser.
Additionally, the <code>JColorChooser</code> class provides two
methods that make it easy to use a color chooser within a dialog.
<p>
The rest of this section discusses these topics:
<ul>
<li> <a href="#advancedexample">Another Example: ColorChooserDemo2</a>
<li> <a href="#dialog">Showing a Color Chooser in a Dialog</a>
<li> <a href="#previewpanel">Removing or Replacing the Preview Panel</a>
<li> <a href="#chooserpanel">Creating a Custom Chooser Panel</a>
<li> <a href="#api">The Color Chooser API</a>
<li> <a href="#eg">Examples that Use Color Choosers</a>
</ul>

<a name="advancedexample">
</blockquote>
<h3>Another Example: ColorChooserDemo2</h3>
</a>
<blockquote>
Now let's turn our attention to
<a href="examples/index.html#ColorChooserDemo2">ColorChooserDemo2</a>,
a modified version of the previous demo program that
uses more of the <code>JColorChooser</code> API.
You can 
<a href="http://java.sun.com/docs/books/tutorialJWS/uiswing/components/examples/ColorChooserDemo2.jnlp">run&nbsp;ColorChooserDemo2</a> (it requires release 6)
using 
<a class="TutorialLink" target="_top" href="../../information/javawebstart.html">Java<sup><font size=-2>TM</font></sup> Web Start</a>.  Here's a picture of ColorChooserDemo2:

<p><center><IMG SRC="../../figures/uiswing/components/ColorChooserDemo2Metal.png" WIDTH="387" HEIGHT="425" ALIGN="BOTTOM" ALT="A snapshot of ColorChooserDemo, which contains a custom color chooser."></center></p>
<p>
This program customizes the banner's
text color chooser in these ways:
<ul>
<li> Removes the preview panel
<li> Removes all of the default chooser panels
<li> Adds a custom chooser panel
</ul>
<a href="#previewpanel">Removing or Replacing the Preview Panel</a>
covers the first customization.
<a href="#chooserpanel">Creating a Custom Chooser Panel</a>
discusses the last two.
<p>
This program also adds a button that brings up
a color chooser in a dialog,
which you can use to set the banner's background color.

</blockquote>

<a name="dialog">
<h3>Showing a Color Chooser in a Dialog</h3>
</a>
<blockquote>
The <code>JColorChooser</code> class provides 
two class methods to make it easy to use a color chooser in a
dialog.
ColorChooserDemo2 uses one of these methods,
<code>showDialog</code>,
to display the background color chooser when the user
clicks the <strong>Show Color Chooser...</strong> button.
Here's the single line of code from the example
that brings up the background color chooser in a dialog:
<blockquote><pre>
Color newColor = JColorChooser.showDialog(
                     ColorChooserDemo2.this,
                     "Choose Background Color",
                     banner.getBackground());
</pre></blockquote>
The first argument is the parent for the dialog,
the second is the dialog's title, and
the third is the initially selected color.
<p>
The dialog disappears under three conditions:
the user chooses a color and clicks the <strong>OK</strong> button,
the user cancels the operation with the <strong>Cancel</strong> button,
or the user dismisses the dialog with a frame control.
If the user chooses a color,
the <code>showDialog</code> method returns the new color.
If the user cancels the operation or dismisses the window,
the method returns <code>null</code>.
Here's the code from the example that updates
the banner's background color
according to the value returned by <code>showDialog</code>:
<blockquote><pre>
if (newColor != null) {
    banner.setBackground(newColor);
}
</pre></blockquote>

The dialog created by <code>showDialog</code> is modal.
If you want a non-modal dialog,
you can use <code>JColorChooser</code>'s
<code>createDialog</code> method to create the dialog.
This method also lets you specify action listeners for the
<strong>OK</strong> and <strong>Cancel</strong>
buttons in the dialog window.
Use <code>JDialog</code>'s <code>show</code> method
to display the dialog created by this method.
For an example that uses this method, see
<a href="table.html#editor">Specifying Other Editors</a>
in the
<a href="table.html">How to Use Tables</a> section.
</blockquote>

<a name="previewpanel">
<h3>Removing or Replacing the Preview Panel</h3>
</a>
<blockquote>
By default, the color chooser displays a preview panel.
ColorChooserDemo2
removes the text color chooser's
preview panel with this line of code:

<blockquote><pre>
tcc.setPreviewPanel(new JPanel());
</pre></blockquote>

This effectively removes the preview panel because
a plain <code>JPanel</code> has no size and no default view.
To set the preview panel back to the default,
use <code>null</code> as the argument to <code>setPreviewPanel</code>.
<p>
To provide a custom preview panel,
you also use <code>setPreviewPanel</code>.
The component you pass into the method should
inherit from <code>JComponent</code>,
specify a reasonable size,
and provide a customized view of the current color.
To get notified when the user changes the color
in the color chooser,
the preview panel must register
as a change listener on the color chooser's color selection model
as described <a href="#changelistener">previously</a>.

</blockquote>
<a name="chooserpanel">
<h3>Creating a Custom Chooser Panel</h3>
</a>
<blockquote>
The default color chooser provides three chooser panels:
<ul>
<li> Swatches &#151; for choosing a color from a collection of swatches.
<li> HSB &#151; for choosing a color using the Hue-Saturation-Brightness 
     color model.
<li> RGB &#151; for choosing a color using the Red-Green-Blue
     color model.
</ul>
You can extend the default color chooser
by adding chooser panels of your own design with
<code>addChooserPanel</code>,
or you can limit it by removing chooser panels
with <code>removeChooserPanel</code>.
<p>
If you want to remove all of the default chooser panels
and add one or more of your own, you can do this with a single
call to <code>setChooserPanels</code>.
ColorChooserDemo2
uses this method to replace the default chooser panels
with an instance of

<a class="SourceLink" target="_blank" href="examples/CrayonPanel.java"><code>CrayonPanel</code></a>,
a custom chooser panel.
Here's the call to <code>setChooserPanels</code> from
that example:
<blockquote><pre>
//Override the chooser panels with our own.
AbstractColorChooserPanel panels[] = { new CrayonPanel() };
tcc.setChooserPanels(panels);
</pre></blockquote>
The code is straighforward:
it creates an array containing the <code>CrayonPanel</code>.
Next the code calls <code>setChooserPanels</code> to 
set the contents of the array as the color chooser's
chooser panels.
<p>
<code>CrayonPanel</code> is a subclass of
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/colorchooser/AbstractColorChooserPanel.html"><code>AbstractColorChooserPanel</code></a> and overrides the five abstract methods defined in its superclass:
<dl>

<dt> <strong><code>void buildChooser()</code></strong>
<dd> Creates the GUI that comprises the chooser panel.
     The example creates four toggle buttons
     &#151; one for each crayon &#151;
     and adds them to the chooser panel.

<dt> <strong><code>void updateChooser()</code></strong>
<dd> This method is called whenever the chooser panel is displayed.
     The example's implementation of this method selects
     the toggle button that represents the currently
     selected color.
<blockquote><pre>
public void updateChooser() {
    Color color = getColorFromModel();
    if (Color.red.equals(color)) {
        redCrayon.setSelected(true);