JComboBox: adding automatic completion-Binary Lookup and Performance : ComboBox « Swing Components « Java

JComboBox: adding automatic completion-Binary Lookup and Performance

JComboBox: adding automatic completion-Binary Lookup and Performance

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

Author: Thomas Bierhance
Binary Lookup & Performance
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import java.lang.reflect.Field;
import javax.swing.plaf.basic.BasicComboBoxUI;

public class S19PrototypeValue 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;
    public S19PrototypeValue(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;
                    // ignore delete key
                    case KeyEvent.VK_DELETE : e.consume();
        // 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 setPrototypeValue() {
        JList list = getListBox();
        setPrototypeValue(getPrototypeValue(list), list);
    void setPrototypeValue(Object value, JList list) {
    Object getPrototypeValue(JList list) {
        Object prototypeValue=null;
        double prototypeWidth=0;
        ListCellRenderer renderer = comboBox.getRenderer();
        for (int i=0, n=model.getSize(); i<n; i++) {
            Object value = model.getElementAt(i);
            java.awt.Component c = renderer.getListCellRendererComponent(list, value, i, false, false);
            double width = c.getPreferredSize().getWidth();
            if (width>prototypeWidth) {
        return prototypeValue;
    JList getListBox() {
        JList listBox;
        try {
            Field field = JComponent.class.getDeclaredField("ui");
            BasicComboBoxUI ui = (BasicComboBoxUI) field.get(comboBox);
            field = BasicComboBoxUI.class.getDeclaredField("listBox");
            listBox = (JList) field.get(ui);
        } catch (NoSuchFieldException nsfe) {
            throw new RuntimeException(nsfe);
        } catch (IllegalAccessException iae) {
            throw new RuntimeException(iae);
        return listBox;
    public void remove(int offs, int len) throws BadLocationException {
        // return immediately when selecting an item
        if (selecting) return;
        if (hitBackspace) {
            // user hit backspace => 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);
    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()));
        if (item != null) {
        } else {
            // keep old item selected if there is no match
            item = comboBox.getSelectedItem();
            // imitate no insert (later on offs will be incremented by str.length(): selection won't move forward)
            offs = offs-str.length();
            // provide feedback to the user that his input has been received but can not be accepted
            comboBox.getToolkit().beep(); // when available use: UIManager.getLookAndFeel().provideErrorFeedback(comboBox);
        // select the completed part
    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)) {
            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 S19PrototypeValue(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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