combobox.html

jsf、swing的官方指南

class ComboBoxRenderer extends JLabel
                       implements ListCellRenderer {
    . . .
    public ComboBoxRenderer() {
        setOpaque(true);
        setHorizontalAlignment(CENTER);
        setVerticalAlignment(CENTER);
    }

    /*
     * This method finds the image and text corresponding
     * to the selected value and returns the label, set up
     * to display the text and image.
     */
    public Component getListCellRendererComponent(
                                       JList list,
                                       Object value,
                                       int index,
                                       boolean isSelected,
                                       boolean cellHasFocus) {
        //Get the selected index. (The index param isn't
        //always valid, so just use the value.)
        int selectedIndex = ((Integer)value).intValue();

        if (isSelected) {
            setBackground(list.getSelectionBackground());
            setForeground(list.getSelectionForeground());
        } else {
            setBackground(list.getBackground());
            setForeground(list.getForeground());
        }

        //Set the icon and text.  If icon was null, say so.
        ImageIcon icon = images[selectedIndex];
        String pet = petStrings[selectedIndex];
        setIcon(icon);
        if (icon != null) {
            setText(pet);
            setFont(list.getFont());
        } else {
            setUhOhText(pet + " (no image available)",
                        list.getFont());
        }

        return this;
    }
    . . .
}
</pre></blockquote>

As a <code>ListCellRenderer</code>,
<code>ComboBoxRenderer</code> implements a method
called <code>getListCellRendererComponent</code>,
which returns a component whose <code>paintComponent</code>
method is used to display the combo box and each of its items.
The easiest way to display an image and an icon
is to use a label.
So <code>ComboBoxRenderer</code> is a subclass of label
and returns itself.
The implementation of <code>getListCellRendererComponent</code>
configures the renderer to display the currently selected
icon and its description.
<p>
These arguments are passed to <code>getListCellRendererComponent</code>:
<ul>
<li> <code>JList list</code> &#151;
	a list object used behind the scenes
        to display the items.
        The example uses this object's colors
        to set up foreground and background colors.
<li> <code>Object value</code> &#151;
	the object to render.
        An <code>Integer</code> in this example.
<li> <code>int index</code> &#151;
	the index of the object to render.
<li> <code>boolean isSelected</code> &#151;
	indicates whether the
        object to render is selected.
        Used by the example to determine which colors to use.
<li> <code>boolean cellHasFocus</code> &#151;
	indicates whether the
        object to render has the focus.
</ul>

Note that combo boxes and <a href="list.html">lists</a>
use the same type of renderer &#151;
<code>ListCellRenderer</code>.
You can save yourself some time
by sharing renderers between
combo boxes and lists,
if it makes sense for your program.
</blockquote>

<h3>
<a name="api">The Combo Box API</a>
</h3>
<blockquote>
The following tables list the commonly used
<code>JComboBox</code> constructors and methods.
Other methods you are most likely to invoke on
a <code>JComboBox</code> object are those
it inherits from its superclasses,
such as <code>setPreferredSize</code>.
See
<a href="jcomponent.html#api">The JComponent API</a>
for tables of commonly used inherited methods.

<p>

The API for using combo boxes falls into two categories:

<ul>
<li><a href="#list">Setting or Getting the Items in the Combo Box's Menu</a>
<li><a href="#configuring">Customizing the Combo Box's Operation</a>
</ul>

<p>

<table border=1>
<caption><a name="list">Setting or Getting the Items in the Combo Boxes's Menu</a></caption>

<tr>
<th>Method
</th>
<th>Purpose

</th>
</tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#JComboBox()">JComboBox()</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#JComboBox(javax.swing.ComboBoxModel)">JComboBox(ComboBoxModel)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#JComboBox(java.lang.Object[])">JComboBox(Object[])</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#JComboBox(java.util.Vector)">JComboBox(Vector)</a>    </td>
    <td>Create a combo box with the specified items in its menu.
        A combo box created with the default constructor has no
        items in the menu initially.
        Each of the other constructors initializes the menu
        from its argument: a model object,
        an array of objects, or a <code>Vector</code> of objects.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#addItem(java.lang.Object)">void addItem(Object)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#insertItemAt(java.lang.Object, int)">void insertItemAt(Object, int)</a>    </td>
    <td>Add or insert the specified object into the combo box's menu.
        The insert method places the specified object <em>at</em>
        the specified index, thus inserting it before the object currently
        at that index.
        These methods require that the combo box's data model
        be an instance of <code>MutableComboBoxModel</code>.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getItemAt(int)">Object getItemAt(int)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getSelectedItem()">Object getSelectedItem()</a>    </td>
    <td>Get an item from the combo box's menu.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#removeAllItems()">void removeAllItems()</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#removeItemAt(int)">void removeItemAt(int)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#removeItem(java.lang.Object)">void removeItem(Object)</a>    </td>
    <td>Remove one or more items from the combo box's menu.
        These methods require that the combo box's data model
        be an instance of <code>MutableComboBoxModel</code>.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getItemCount()">int getItemCount()</a>    </td>
    <td>Get the number of items in the combo box's menu.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#setModel(javax.swing.ComboBoxModel)">void setModel(ComboBoxModel)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getModel()">ComboBoxModel getModel()</a>    </td>
    <td>Set or get the data model that provides the items in the combo box's menu.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#setAction(javax.swing.Action)">void setAction(Action)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getAction()">Action getAction()</a>    </td>
    <td>Set or get the <code>Action</code>
        associated with the combo box.
        For further information, see
<a class="TutorialLink" target="_top" href="../misc/action.html">How to Use Actions</a>.
    </td>
  </tr>
</table>

<p>

<table border=1>
<caption><a name="configuring">Customizing the Combo Box's Operation</a></caption>

<tr>
<th>Method or Constructor
</th>
<th>Purpose

</th>
</tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#addActionListener(java.awt.event.ActionListener)">void addActionListener(ActionListener)</a>    </td>
    <td>Add an action listener to the combo box.
        The listener's <code>actionPerformed</code> method is called
        when the user selects an item from the combo box's menu
        or, in an editable combo box, when the user presses Enter.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#addItemListener(java.awt.event.ItemListener)">void addItemListener(ItemListener)</a>    </td>
    <td>Add an item listener to the combo box.
        The listener's <code>itemStateChanged</code> method is called
        when the selection state of any of the combo box's items change.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#setEditable(boolean)">void setEditable(boolean)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#isEditable()">boolean isEditable()</a>    </td>
    <td>Set or get whether the user can type in the combo box.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#setRenderer(javax.swing.ListCellRenderer)">void setRenderer(ListCellRenderer)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getRenderer()">ListCellRenderer getRenderer()</a>    </td>
    <td>Set or get the object responsible for painting
        the selected item in the combo box.
        The renderer is used only when the combo box is uneditable.
        If the combo box is editable,
        the editor is used to paint the selected item instead.

    </td>
  </tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#setEditor(javax.swing.ComboBoxEditor)">void setEditor(ComboBoxEditor)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JComboBox.html#getEditor()">ComboBoxEditor getEditor()</a>    </td>
    <td>Set or get the object responsible for painting and editing
        the selected item in the combo box.
        The editor is used only when the combo box is editable.
        If the combo box is uneditable, the renderer is used to paint
        the selected item instead.
    </td>
  </tr>
</table>
</blockquote>

<h3>
<a name="eg">Examples that Use Combo Boxes</a>
</h3>
<blockquote>
This table shows the examples that use <code>JComboBox</code>
and where those examples are described.
<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#ComboBoxDemo"><code>ComboBoxDemo</code></a>
</td>
<td> This section
</td>
<td> Uses an uneditable combo box.

</td>
</tr>
<tr>
<td> <a href="examples/index.html#ComboBoxDemo2"><code>ComboBoxDemo2</code></a>
</td>
<td> This section
</td>
<td> Uses an editable combo box.

</td>
</tr>
<tr>
<td> <a href="examples/index.html#CustomComboBoxDemo"><code>CustomComboBoxDemo</code></a>
</td>
<td> This section
</td>
<td> Provides a custom renderer for a combo box.

</td>
</tr>
<tr>
<td><a href="examples/index.html#TableRenderDemo"><code>TableRenderDemo</code></a>
</td>
<td>How to Use Tables (<a href="table.html#combobox">Using a Combo Box as an
Editor</a>)
</td>
<td>Shows how to use a combo box as a table cell editor.
</td>
</tr>
</table>

</blockquote>


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