Using JComboBox as a Search

Question

I want to know how to get an JComboBox to auto suggest the elements when we type in the combo box. For an example, If I had loaded a JComboBox with these names using MySQL, [Amila, Nimila, Nikila, Sunil] and when I type "N" inside the Combo Box, it'll drop down the list only showing Nimila & Nikila as suggestions. And I'm trying to do this on NetBeans. Thanks.

Answer 1

Possible Duplicate JComboBox autocomplete. However if you want to use a pure swing based solution follow this article. it's quite comprehensive

http://www.orbital-computer.de/JComboBox/

If you want the quick and easy solution, simply add this class to your project;

import java.awt.event.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.*;
import javax.swing.text.*;

/* This work is hereby released into the Public Domain.
 * To view a copy of the public domain dedication, visit
 * http://creativecommons.org/licenses/publicdomain/
 */
public class AutoCompletion 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;

KeyListener editorKeyListener;
FocusListener editorFocusListener;

public AutoCompletion(final JComboBox comboBox) {
    this.comboBox = comboBox;
    model = comboBox.getModel();
    comboBox.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            if (!selecting) highlightCompletedText(0);
        }
    });
    comboBox.addPropertyChangeListener(new PropertyChangeListener() {
        public void propertyChange(PropertyChangeEvent e) {
            if (e.getPropertyName().equals("editor")) configureEditor((ComboBoxEditor) e.getNewValue());
            if (e.getPropertyName().equals("model")) model = (ComboBoxModel) e.getNewValue();
        }
    });
    editorKeyListener = new KeyAdapter() {
        public void keyPressed(KeyEvent e) {
            if (comboBox.isDisplayable()) comboBox.setPopupVisible(true);
            hitBackspace=false;
            switch (e.getKeyCode()) {
                // determine if the pressed key is backspace (needed by the remove method)
                case KeyEvent.VK_BACK_SPACE : hitBackspace=true;
                hitBackspaceOnSelection=editor.getSelectionStart()!=editor.getSelectionEnd();
                break;
                // ignore delete key
                case KeyEvent.VK_DELETE : e.consume();
                comboBox.getToolkit().beep();
                break;
            }
        }
    };
    // Bug 5100422 on Java 1.5: Editable JComboBox won't hide popup when tabbing out
    hidePopupOnFocusLoss=System.getProperty("java.version").startsWith("1.5");
    // Highlight whole text when gaining focus
    editorFocusListener = new FocusAdapter() {
        public void focusGained(FocusEvent e) {
            highlightCompletedText(0);
        }
        public void focusLost(FocusEvent e) {
            // Workaround for Bug 5100422 - Hide Popup on focus loss
            if (hidePopupOnFocusLoss) comboBox.setPopupVisible(false);
        }
    };
    configureEditor(comboBox.getEditor());
    // Handle initially selected object
    Object selected = comboBox.getSelectedItem();
    if (selected!=null) setText(selected.toString());
    highlightCompletedText(0);
}

public static void enable(JComboBox comboBox) {
    // has to be editable
    comboBox.setEditable(true);
    // change the editor's document
    new AutoCompletion(comboBox);
}

void configureEditor(ComboBoxEditor newEditor) {
    if (editor != null) {
        editor.removeKeyListener(editorKeyListener);
        editor.removeFocusListener(editorFocusListener);
    }

    if (newEditor != null) {
        editor = (JTextComponent) newEditor.getEditorComponent();
        editor.addKeyListener(editorKeyListener);
        editor.addFocusListener(editorFocusListener);
        editor.setDocument(this);
    }
}

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);
        }
        highlightCompletedText(offs);
    } 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) {
        setSelectedItem(item);
    } 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);
    }
    setText(item.toString());
    // select the completed part
    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) {
    editor.setCaretPosition(getLength());
    editor.moveCaretPosition(start);
}

private void setSelectedItem(Object item) {
    selecting = true;
    model.setSelectedItem(item);
    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 (currentItem != null && 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)
    final JComboBox comboBox = new JComboBox(new Object[] {"Ester", "Jordi", "Jordina", "Jorge", "Sergi"});
    enable(comboBox);

    // create and show a window containing the combo box
    final JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(3);
    frame.getContentPane().add(comboBox);
    frame.pack(); frame.setVisible(true);
}


public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
}
}

And then, to add the AutoCompletion feature to a JComboBox simply call;

AutoCompletion.enable(yourComboBox);