JComboBox Key Event Selection

Posted on 2006-05-25
Last Modified: 2009-12-16
I have a JComboBox that I want to respond to key events for selecting the item in the list.

For instance:

Vector people = new Vector();

JComboBox comboBox = new JComboBox(people);

When you select the Combo box and press the letter "S" it goes to Sam. However when you press "Saw", it does not go to Sawyer. Is there a way to do this? I wasn't sure what this technique is really called otherwise I would have googled it more.
Question by:Hokester
    LVL 2

    Accepted Solution


    Selecting an Item in a JComboBox Component with Multiple Keystrokes

    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.

    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.

        // Create a read-only combobox
        String[] items = {"Ant", "Ape", "Bat", "Boa", "Cat", "Cow"};
        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;
                // 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;

    Author Comment

    Thanks! This looks EXACTLY like what I was looking for!

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