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<TITLE>Selecting an Item in a JComboBox Component with Multiple Keystrokes (Java Developers Almanac Example)
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<h3>e760. Selecting an Item in a JComboBox Component with Multiple Keystrokes</h3>
By default, when the user types a keystroke in a read-only combobox and an
item in the combobox starts with the typed keystroke, the combobox will
select that item. This behavior is not ideal if there are multiple
items that start with the same letter.
<P> This example demonstrates how to customize a combobox so that
it will select an item based on multiple keystrokes. More
specifically, if a keystroke is typed within 300 milliseconds of the
previous keystroke, the new keystroke is appended to the previous
keystroke, and the combobox will select an item that starts with both
keystrokes.
<pre> // Create a read-only combobox
String[] items = {<font color="#0066ff"><i>"Ant", "Ape", "Bat", "Boa", "Cat", "Cow"</i></font>};
JComboBox cb = new JComboBox(items);
// Install the custom key selection manager
cb.setKeySelectionManager(new MyKeySelectionManager());
// This key selection manager will handle selections based on multiple keys.
class MyKeySelectionManager implements JComboBox.KeySelectionManager {
long lastKeyTime = 0;
String pattern = "";
public int selectionForKey(char aKey, ComboBoxModel model) {
// Find index of selected item
int selIx = 01;
Object sel = model.getSelectedItem();
if (sel != null) {
for (int i=0; i<model.getSize(); i++) {
if (sel.equals(model.getElementAt(i))) {
selIx = i;
break;
}
}
}
// Get the current time
long curTime = System.currentTimeMillis();
// If last key was typed less than 300 ms ago, append to current pattern
if (curTime - lastKeyTime < 300) {
pattern += ("" + aKey).toLowerCase();
} else {
pattern = ("" + aKey).toLowerCase();
}
// Save current time
lastKeyTime = curTime;
// Search forward from current selection
for (int i=selIx+1; i<model.getSize(); i++) {
String s = model.getElementAt(i).toString().toLowerCase();
if (s.startsWith(pattern)) {
return i;
}
}
// Search from top to current selection
for (int i=0; i<selIx ; i++) {
if (model.getElementAt(i) != null) {
String s = model.getElementAt(i).toString().toLowerCase();
if (s.startsWith(pattern)) {
return i;
}
}
}
return -1;
}
}
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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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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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e763. <a class="eglink" href="combobox_CbIsKeySel.html?l=rel">
Displaying the Menu in a JComboBox Component Using a Keystroke If the Selected Item Is Not Unique
</a>
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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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