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<TITLE>Displaying the Menu in a JComboBox Component Using a Keystroke If the Selected Item Is Not Unique (Java Developers Almanac Example)
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<h3>e763. Displaying the Menu in a JComboBox Component Using a Keystroke If the Selected Item Is Not Unique</h3>
This example registers a key listener in a read-only combobox that
displays the menu if the newly selected item is not unique.
<pre> // Create a read-only combobox
String[] items = {<font color="#0066ff"><i>"Ant", "Ape", "Bat", "Boa", "Cat"</i></font>};
JComboBox cb = new JComboBox(items);
// Create and register the key listener
cb.addKeyListener(new MyKeyListener());
// This key listener displays the menu only if the pressed key
// does not select a new item or if the selected item is not unique.
class MyKeyListener extends KeyAdapter {
public void keyPressed(KeyEvent evt) {
JComboBox cb = (JComboBox)evt.getSource();
// At this point, the selection in the combobox has already been
// changed; get the index of the new selection
int curIx = cb.getSelectedIndex();
// Get pressed character
char ch = evt.getKeyChar();
// Get installed key selection manager
JComboBox.KeySelectionManager ksm = cb.getKeySelectionManager();
if (ksm != null) {
// Determine if another item has the same prefix
int ix = ksm.selectionForKey(ch, cb.getModel());
boolean noMatch = ix < 0;
boolean uniqueItem = ix == curIx;
// Display menu if no matching items or the if the selection is not unique
if (noMatch || !uniqueItem) {
cb.showPopup();
}
}
}
}
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<b>Related Examples</b></font></td>
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e756. <a class="eglink" href="combobox_CbRead.html?l=rel">
Creating a JComboBox Component
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e757. <a class="eglink" href="combobox_CbGetCur.html?l=rel">
Getting and Setting the Selected Item in a JComboBox Component
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e758. <a class="eglink" href="combobox_CbGetItems.html?l=rel">
Getting the Items in a JComboBox Component
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e759. <a class="eglink" href="combobox_CbAddItems.html?l=rel">
Adding and Removing an Item in a JComboBox Component
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e760. <a class="eglink" href="combobox_CbMultiKey.html?l=rel">
Selecting an Item in a JComboBox Component with Multiple Keystrokes
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e761. <a class="eglink" href="combobox_CbIsMenu.html?l=rel">
Determining If the Menu of a JComboBox Component Is Visible
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e762. <a class="eglink" href="combobox_CbKeyPopup.html?l=rel">
Displaying the Menu in a JComboBox Component Using a Keystroke
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e764. <a class="eglink" href="combobox_CbScrollList.html?l=rel">
Setting the Number of Visible Items in the Menu of a JComboBox Component
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e765. <a class="eglink" href="combobox_CbItemEvt.html?l=rel">
Listening for Changes to the Selected Item in a JComboBox Component
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e766. <a class="eglink" href="combobox_CbActionEvt.html?l=rel">
Listening for Action Events from a JComboBox Component
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e767. <a class="eglink" href="combobox_CbMenuEvt.html?l=rel">
Determining When the Menu of a JComboBox Component Is Displayed
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JLabel
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JList
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JProgressBar
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JRadioButton
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JToolBar
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Keystrokes and Input Maps
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Progress Monitor
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The Screen
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Tool Tips
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UI Default Values
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