JComboBox: adding automatic completion-Non-strict matching 2 : ComboBox « Swing Components « Java

JComboBox: adding automatic completion-Non-strict matching 2

JComboBox: adding automatic completion-Non-strict matching 2

//Code from: http://www.orbital-computer.de/JComboBox/
Inside JComboBox: adding automatic completion

Author: Thomas Bierhance

This works, but has some inconveniences:

   1. The case-insensitive match makes it impossible to enter new items with correct case. Suppose you want to enter "EsTonto". Entering 'E' will result in "Ester" being selected. You enter 's','T',... resulting in "Estonto". But you wanted an uppercase 'T'...
   2. The backspace key should not only move the selection backwards when editing "new" items. Suppose you had entered "Esters" and you want to delete the trailing 's'. Hitting backspace will highlight the 's' but won't delete it.

The first issue can't be resolved very easily. Each insert would be written to a protocoll and later the original string could be reconstructed (here's the difficult part). I did a hack that is not really worth to be published but you can contact me, if you can't live without this feature.

The second needed some coding. It won't be explained here in more detail.

import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;

public class S18NonStrictBackspace extends PlainDocument {
    JComboBox comboBox;
    ComboBoxModel model;
    JTextComponent editor;
    // flag to indicate if setSelectedItem has been called
    // subsequent calls to remove/insertString should be ignored
    boolean selecting=false;
    boolean hidePopupOnFocusLoss;
    boolean hitBackspace=false;
    boolean hitBackspaceOnSelection;
    boolean listContainsSelectedItem;
    public S18NonStrictBackspace(final JComboBox comboBox) {
        this.comboBox = comboBox;
        model = comboBox.getModel();
        editor = (JTextComponent) comboBox.getEditor().getEditorComponent();
        comboBox.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (!selecting) highlightCompletedText(0);
        editor.addKeyListener(new KeyAdapter() {
            public void keyPressed(KeyEvent e) {
                if (comboBox.isDisplayable()) comboBox.setPopupVisible(true);
                switch (e.getKeyCode()) {
                    // determine if the pressed key is backspace (needed by the remove method)
                    case KeyEvent.VK_BACK_SPACE : hitBackspace=true;
        // Bug 5100422 on Java 1.5: Editable JComboBox won't hide popup when tabbing out
        // Highlight whole text when gaining focus
        editor.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent e) {
            public void focusLost(FocusEvent e) {
                // Workaround for Bug 5100422 - Hide Popup on focus loss
                if (hidePopupOnFocusLoss) comboBox.setPopupVisible(false);
        // Handle initially selected object
        Object selected = comboBox.getSelectedItem();
        if (selected!=null) setText(selected.toString());
    public void remove(int offs, int len) throws BadLocationException {
        // return immediately when selecting an item
        if (selecting) return;
        if (hitBackspace) {
            if (listContainsSelectedItem) {
                // move the selection backwards
                // old item keeps being selected
                if (offs>0) {
                    if (hitBackspaceOnSelection) offs--;
                } else {
                    // User hit backspace with the cursor positioned on the start => beep
                    comboBox.getToolkit().beep(); // when available use: UIManager.getLookAndFeel().provideErrorFeedback(comboBox);
            } else {
                super.remove(offs, len);
                String currentText = getText(0, getLength());
                // lookup if a matching item exists
                Object item = lookupItem(currentText);
                if (item != null) {
                    System.out.println("'" + item + "' matches.");
                } else {
                    System.out.println("No match. Selecting '" + currentText + "'.");
                    // no item matches => use the current input as selected item
                // display the completed string
                String itemString=item.toString();
                if (listContainsSelectedItem) highlightCompletedText(offs);
        } else {
            super.remove(offs, len);
            setSelectedItem(getText(0, getLength()));
    public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
        // return immediately when selecting an item
        if (selecting) return;
        // insert the string into the document
        super.insertString(offs, str, a);
        // lookup and select a matching item
        Object item = lookupItem(getText(0, getLength()));
        listContainsSelectedItem = true;
        if (item == null) {
            // no item matches => use the current input as selected item
            item=getText(0, getLength());
        // select the completed part
        if (listContainsSelectedItem) highlightCompletedText(offs+str.length());
    private void setText(String text) {
        try {
            // remove all text and insert the completed string
            super.remove(0, getLength());
            super.insertString(0, text, null);
        } catch (BadLocationException e) {
            throw new RuntimeException(e.toString());
    private void highlightCompletedText(int start) {
    private void setSelectedItem(Object item) {
        selecting = true;
        selecting = false;
    private Object lookupItem(String pattern) {
        Object selectedItem = model.getSelectedItem();
        // only search for a different item if the currently selected does not match
        if (selectedItem != null && startsWithIgnoreCase(selectedItem.toString(), pattern) && listContainsSelectedItem) {
            return selectedItem;
        } else {
            // iterate over all items
            for (int i=0, n=model.getSize(); i < n; i++) {
                Object currentItem = model.getElementAt(i);
                // current item starts with the pattern?
                if (startsWithIgnoreCase(currentItem.toString(), pattern)) {
                    return currentItem;
        // no item starts with the pattern => return null
        return null;
    // checks if str1 starts with str2 - ignores case
    private boolean startsWithIgnoreCase(String str1, String str2) {
        return str1.toUpperCase().startsWith(str2.toUpperCase());
    private static void createAndShowGUI() {
        // the combo box (add/modify items if you like to)
        JComboBox comboBox = new JComboBox(new Object[] {"Ester", "Jordi", "Jordina", "Jorge", "Sergi"});
        // has to be editable
        // change the editor's document
        new S18NonStrictBackspace(comboBox);
        // create and show a window containing the combo box
        JFrame frame = new JFrame();
        frame.pack(); frame.setVisible(true);
    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {

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