Swing Hacks

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Chapter 7, Text

#48 Make Text Components Searchable

HACK

different date formats. This hack has much more humble needs, but Java 1.4’s

built-in regex support will make the search implementation very easy.

The plan for this hack is to create a searching utility object that targets a

JTextComponent

(the common subclass for all Swing text components such as

JTextArea

and

JTextField

). It will also listen for action and document

change events from a search component (usually a

JTextField

) to do the

actual searching. By constructing it with class agnostic listeners, you can

add it easily to existing programs without changing much code.

A Basic Search Class

The code in Example 7-1 defines the

IncrementalSearch

class, which imple-

ments the

DocumentListener and ActionListener interfaces. Programs with

search usually have a search field above the search target. The

IncrementalSearch constructor accepts a JTextComponent as the target, and

the document listener events will provide access to the search field itself. In

addition to the usual suspects, you’ll need to import the Swing event, Swing

text, and regex classes.

You can see that all three document listener methods just call

runNewSearch( ),

passing in the document. This forces the search to start over if the user types

new text, hits the Backspace key, or replaces a selection. So far, there is

Example 7-1. Starting the basic incremental search class

import javax.swing.event.*;

import javax.swing.text.*;

import java.util.regex.*;

public class IncrementalSearch

implements DocumentListener, ActionListener {

protected JTextComponent content;

public IncrementalSearch(JTextComponent comp) {

this.content = comp;

}

/* DocumentListener implementation */

public void insertUpdate(DocumentEvent evt) {

runNewSearch(evt.getDocument( ));

}

public void removeUpdate(DocumentEvent evt) {

runNewSearch(evt.getDocument( ));

}

public void changedUpdate(DocumentEvent evt) {

runNewSearch(evt.getDocument( ));

}