Swing Hacks

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Chapter 7, Text

#50 Auto-Completing Text Fields

HACK

The text field that pops up a window of recently viewed sites is a happy

compromise. It jogs your memory by showing you completion options, and

it saves lots of typing by letting you simply click one of the options and hav-

ing that text inserted immediately into the text field.

A Self-Completing Text Field

This hack takes a JTextField and has it manage a JWindow, which contains a

JList of possible completion values. The real work is done by an inner class

that manages the list of completions and has a

javax.util.regex.Pattern

object to match each potential completion against the field’s current text.

Example 7-4 is what you need to get going.

Example 7-4. A JTextField that manages a pop-up list of completions

import java.awt.*;

import javax.swing.*;

import javax.swing.event.*;

import javax.swing.text.*;

import java.util.*;

import java.util.regex.*;

public class CompletableJTextField extends JTextField

implements ListSelectionListener {

Completer completer;

JList completionList;

DefaultListModel completionListModel;

JScrollPane listScroller;

JWindow listWindow;

public CompletableJTextField (int col) {

super (col);

completer = new Completer( );

completionListModel = new DefaultListModel( );

completionList = new JList(completionListModel);

completionList.setSelectionMode (ListSelectionModel.SINGLE_SELECTION);

completionList.addListSelectionListener (this);

listScroller =

new JScrollPane (completionList,

ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,

ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

listWindow = new JWindow( );

listWindow.getContentPane( ).add (listScroller);

}

public void addCompletion (String s) {

completer.addCompletion (s); }

Auto-Completing Text Fields #50

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267

HACK

public void removeCompletion (String s) {

completer.removeCompletion (s); }

public void clearCompletions (String s ) {

completer.clearCompletions ( ); }

public void valueChanged (ListSelectionEvent e) {

if (e.getValueIsAdjusting( )) { return; }

if (completionList.getModel().getSize( ) == 0) {return;}

listWindow.setVisible (false);

final String completionString =

(String) completionList.getSelectedValue( );

Thread worker = new Thread( ) {

public void run( ) {

setText (completionString);

}

};

SwingUtilities.invokeLater (worker);

}

/** inner class does the matching of the JTextField's

document to completion strings kept in an ArrayList

*/

class Completer implements DocumentListener {

private Pattern pattern;

private ArrayList completions;

public Completer( ) {

completions = new ArrayList( );

getDocument( ).addDocumentListener (this);

}

public void addCompletion (String s) {

completions.add (s);

buildAndShowPopup( );

}

public void removeCompletion (String s) {

completions.remove (s);

buildAndShowPopup( );

}

public void clearCompletions ( ) {

completions.clear( );

buildPopup( );

listWindow.setVisible(false);

}

private void buildPopup( ) {

completionListModel.clear( );

System.out.println ("buildPopup for " + completions.size( ) +

" completions");

Example 7-4. A JTextField that manages a pop-up list of completions (continued)

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Chapter 7, Text

#50 Auto-Completing Text Fields

HACK

Iterator it = completions.iterator( );

pattern = Pattern.compile (getText( ) + ".+");

while (it.hasNext( )) {

// check if match

String completion = (String) it.next( );

Matcher matcher = pattern.matcher (completion);

if (matcher.matches( )) {

// add if match

System.out.println ("matched "+ completion);

completionListModel.add (completionListModel.getSize( ),

completion);

} else {

System.out.println ("pattern " +

pattern.pattern( ) +

" does not match " +

completion);

}

}

}

private void showPopup( ) {

if (completionListModel.getSize( ) == 0) {

listWindow.setVisible(false);

return;

}

// figure out where the text field is,

// and where its bottom left is

java.awt.Point los = getLocationOnScreen( );

int popX = los.x;

int popY = los.y + getHeight( );

listWindow.setLocation (popX, popY);

listWindow.pack( );

listWindow.setVisible(true);

}

private void buildAndShowPopup( ) {

if (getText().length( ) < 1)

return;

buildPopup( );

showPopup( );

}

// DocumentListener implementation

public void insertUpdate (DocumentEvent e) { buildAndShowPopup( ); }

public void removeUpdate (DocumentEvent e) { buildAndShowPopup( ); }

public void changedUpdate (DocumentEvent e) { buildAndShowPopup( ); }

}

}

Example 7-4. A JTextField that manages a pop-up list of completions (continued)