JComboBox: adding automatic completion-Popup the item list : ComboBox « Swing Components « Java






JComboBox: adding automatic completion-Popup the item list

JComboBox: adding automatic completion-Popup the item list
  
//Code from: http://www.orbital-computer.de/JComboBox/
/*
Inside JComboBox: adding automatic completion

Author: Thomas Bierhance
        thomas@orbital-computer.de
*/
/*
Popup the item list when the user starts typing

One information that the user would like to have is the "neighbourhood" of the selected item (as has been described at the beginning). It would be nice to have the item list to popup when the user starts typing. The easiest solution is easy to add a KeyListener and call JComboBox.setPopupVisible whenever a keystroke is detected...

editor.addKeyListener(new KeyAdapter() {
  public void keyPressed(KeyEvent e) {
    if (comboBox.isDisplayable()) comboBox.setPopupVisible(true);
  }
});

Note that calls to setPopupVisible() might fail (IllegalComponentStateException) when the combo box is not visible. A check is done to prevent this from happening although a keystroke on the editor is unlikely to occur when the combo box is not visible ;-)


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

public class S09ShowPopup 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;
    
    public S09ShowPopup(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);
            }
        });
    }
    
    public void remove(int offs, int len) throws BadLocationException {
        // return immediately when selecting an item
        if (selecting) return;
        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) throws BadLocationException {
        // remove all text and insert the completed string
        super.remove(0, getLength());
        super.insertString(0, text, null);
    }
    
    private void highlightCompletedText(int start) {
        editor.setSelectionStart(start);
        editor.setSelectionEnd(getLength());
    }
    
    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 (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
        comboBox.setEditable(true);
        // get the combo boxes editor component
        JTextComponent editor = (JTextComponent) comboBox.getEditor().getEditorComponent();
        // change the editor's document
        editor.setDocument(new S09ShowPopup(comboBox));
        
        // create and show a window containing the combo box
        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();
            }
        });
    }
}

           
         
    
  








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