JComboBox: adding automatic completion-Pressing backspace at the beginning : ComboBox « Swing Components « Java

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Java » Swing Components » ComboBoxScreenshots 
JComboBox: adding automatic completion-Pressing backspace at the beginning
JComboBox: adding automatic completion-Pressing backspace at the beginning
  

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

Author: Thomas Bierhance
        thomas@orbital-computer.de
*/

/*
You might have noticed two remaining bugs: Pressing backspace at the beginning (e.g. when 
the complete text is highlighted) results in an IllegalArgumentException. Another 
inconvenience is that when the cursor is positioned on the end pressing backspace extends the 
selection to the last two characters not only to the last one. To solve this we also need to 
know if something was selected when the user hit backspace. Another variable to indicate this 
is introduced and the KeyListener and the remove method are modified accordingly. I also 
chose to ignore the deletion key...

editor.addKeyListener(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();
        UIManager.getLookAndFeel().provideErrorFeedback(comboBox);
        break;
    }
  }
});

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
      UIManager.getLookAndFeel().provideErrorFeedback(comboBox);
    }
    highlightCompletedText(offs);
  } else {
    super.remove(offs, len);
  }
}
*/
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;

public class S15WorkingBackspace 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 S15WorkingBackspace(final JComboBox comboBox) {
        this.comboBox = comboBox;
        model = comboBox.getModel();
        editor = (JTextComponentcomboBox.getEditor().getEditorComponent();
        editor.setDocument(this);
        comboBox.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (!selectinghighlightCompletedText(0);
            }
        });
        editor.addKeyListener(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
        editor.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent e) {
                highlightCompletedText(0);
            }
            public void focusLost(FocusEvent e) {
                // Workaround for Bug 5100422 - Hide Popup on focus loss
                if (hidePopupOnFocusLosscomboBox.setPopupVisible(false);
            }
        });
        // Handle initially selected object
        Object selected = comboBox.getSelectedItem();
        if (selected!=nullsetText(selected.toString());
        highlightCompletedText(0);
    }
    
    public void remove(int offs, int lenthrows BadLocationException {
        // return immediately when selecting an item
        if (selectingreturn;
        if (hitBackspace) {
            // user hit backspace => move the selection backwards
            // old item keeps being selected
            if (offs>0) {
                if (hitBackspaceOnSelectionoffs--;
            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 athrows BadLocationException {
        // return immediately when selecting an item
        if (selectingreturn;
        // 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 (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);
        // change the editor's document
        new S15WorkingBackspace(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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