Question

So, I have a program with JTextArea with DocumentFilter. It should (among other things) filter out tab characters and prevent them to be entered in the JTextArea completely.

Well, it works well when I type, but I can still paste it in. i shouldn’t be able to, according to the code…

Below is kind of a SSCCE. Just run it, press ctrl+n and enter. All the colored fileds are JTextAreas with same DocumentFilter. The filter itself is the first class (DefaultDocFilter), only thing you need to look into.

package core;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Locale;
import java.util.Properties;
import java.util.ResourceBundle;

import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.KeyStroke;
import javax.swing.border.Border;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import javax.swing.text.JTextComponent;

class DefaultDocFilter extends DocumentFilter
{
    public void insertString(FilterBypass fb, int offs,String str, AttributeSet a) throws BadLocationException 
    {
        if ((fb.getDocument().getLength() + str.length()) <= 200)
        {
            str.replaceAll("\n", " ");
            str.replaceAll("\t", " ");
            System.out.print(str);
            fb.insertString(offs, str, a);
        }
        else
        {
            int spaceLeft = 200 - fb.getDocument().getLength();
            if (spaceLeft <= 0)
                return;

            str.substring(0, spaceLeft);
            str.replaceAll("\n", " ");
            str.replaceAll("\t", " ");

            fb.insertString(offs, str, a);
        }
    }

    public void replace(FilterBypass fb, int offs, int length, String str, AttributeSet a) throws BadLocationException 
    {
        if (str.equals("\n") || str.equals("\t"))
        { 
            str = "";
        }
        if ((fb.getDocument().getLength() + str.length() - length) <= 200)
        {
            str.replaceAll("\n", " ");
            str.replaceAll("\t", " ");
            fb.replace(offs, length, str, a);
        }
        else
        {
            int spaceLeft = 200 - fb.getDocument().getLength() + length;
            if (spaceLeft <= 0)
                return;

            fb.replace(offs, length, str.substring(0,spaceLeft).replaceAll("\n", " "), a);
        }
    }
}

@SuppressWarnings("serial")
class DefaultFont extends Font
{
    public DefaultFont()
    {
        super("Arial", PLAIN, 20);
    }
}


@SuppressWarnings("serial")
class Page extends JPanel
{
    public JPanel largePage;
    public int content;

    public Page(JPanel panel, int index)
    {
        largePage = new JPanel();
        largePage.setLayout(new BoxLayout(largePage, BoxLayout.Y_AXIS));
        largePage.setMaximumSize(new Dimension(794, 1123));
        largePage.setPreferredSize(new Dimension(794, 1123));
        largePage.setAlignmentX(Component.CENTER_ALIGNMENT);
        largePage.setBackground(Color.WHITE);
        largePage.add(new Box.Filler(new Dimension(0, 96), new Dimension(0, 96), new Dimension(0, 96)));

        setMaximumSize(new Dimension(556, 931));
        setBackground(Color.LIGHT_GRAY);
        setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        add(new Box.Filler(new Dimension(556, 0), new Dimension(556, 931), new Dimension(556, 931)));

        largePage.add(this);
        largePage.add(new Box.Filler(new Dimension(0, 96), new Dimension(0, 96), new Dimension(0, 96)));

        panel.add(largePage, index);
        panel.add(new Box.Filler(new Dimension(0, 40), new Dimension(0, 40), new Dimension(0, 40)));

        content = 0;

        Main.pages.add(this);
    }
}

@SuppressWarnings("serial")
class Heading extends JTextArea
{
    public boolean type;
    public AbstractDocument doc;
    public ArrayList<JPanel/*Question*/> questions;
    public ArrayList<JPanel/*List*/> list;  

    public Heading(boolean segment, Page page)
    {
        type = segment;

        setBackground(Color.RED);
        setFont(new Font("Arial", Font.BOLD, 20));

        Border in = BorderFactory.createDashedBorder(Color.BLACK);
        Border out = BorderFactory.createMatteBorder(0, 0, 10, 0, Color.WHITE);

        setBorder(BorderFactory.createCompoundBorder(out, in));
        setLineWrap(true);
        setWrapStyleWord(true);

        setText("Heading 1 Heading 1 Heading 1 Heading 1");

        doc = (AbstractDocument)this.getDocument();
        doc.setDocumentFilter(new DefaultDocFilter());

        page.add(this, 0);
        page.content++;

        if (type)
        {
            questions = new ArrayList<JPanel>();
        }
        else
        {
            list = new ArrayList<JPanel>();
        }
    }
}

@SuppressWarnings("serial")
class Question extends JPanel
{
    public JPanel questionArea, numberArea, answerArea;
    public JLabel number;
    public JTextArea question;
    public AbstractDocument doc;

    public Question(Page page, int pageNum, int index)
    {
        setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        setBorder(BorderFactory.createMatteBorder(0, 0, 5, 0, Color.WHITE));

        questionArea = new JPanel();
        questionArea.setLayout(new BoxLayout(questionArea, BoxLayout.X_AXIS));
        questionArea.setBorder(BorderFactory.createMatteBorder(0, 0, 8, 0, Color.WHITE));

        numberArea = new JPanel();
        numberArea.setLayout(new BorderLayout());
        numberArea.setBackground(Color.WHITE);

        number = new JLabel(pageNum+".  ", JLabel.RIGHT);
        number.setMinimumSize(new Dimension(100, 20));
        number.setPreferredSize(new Dimension(100, 20));
        number.setMaximumSize(new Dimension(100, 20));
        number.setFont(new Font("Arial", Font.PLAIN, 17));

        numberArea.add(number, BorderLayout.NORTH);

        questionArea.add(numberArea);

        question = new JTextArea();
        question.setFont(new Font("Arial", Font.PLAIN, 17));
        question.setBorder(BorderFactory.createDashedBorder(Color.BLACK));
        question.setLineWrap(true);
        question.setWrapStyleWord(true);
        question.setBackground(Color.GREEN);

        question.setText("Is this the first question?");

        doc = (AbstractDocument)question.getDocument();
        doc.setDocumentFilter(new DefaultDocFilter());

        questionArea.add(question);

        add(questionArea);

        answerArea = new JPanel();
        answerArea.setLayout(new BoxLayout(answerArea, BoxLayout.Y_AXIS));

        add(answerArea);

        page.add(this, index);
        page.content++;
    }
}

@SuppressWarnings("serial")
class Answer extends JPanel
{
    public JPanel letterArea;
    public JLabel letter;
    public JTextArea answer;
    public AbstractDocument doc;

    public Answer(Question q, int index)
    {
        setLayout(new BoxLayout(this, BoxLayout.X_AXIS));

        letterArea = new JPanel();
        letterArea.setLayout(new BorderLayout());
        letterArea.setBackground(Color.WHITE);

        letter = new JLabel((char)(index+96)+")  ", JLabel.RIGHT);
        letter.setMinimumSize(new Dimension(150, 20));
        letter.setPreferredSize(new Dimension(150, 20));
        letter.setMaximumSize(new Dimension(150, 20));
        letter.setFont(new Font("Arial", Font.PLAIN, 17));

        letterArea.add(letter, BorderLayout.NORTH);

        add(letterArea);

        answer = new JTextArea();
        answer.setFont(new Font("Arial", Font.PLAIN, 17));

        Border in = BorderFactory.createDashedBorder(Color.BLACK);
        Border out = BorderFactory.createMatteBorder(0, 0, 5, 0, Color.WHITE);

        answer.setBorder(BorderFactory.createCompoundBorder(out, in));
        answer.setLineWrap(true);
        answer.setWrapStyleWord(true);

        answer.addKeyListener(new KeyListener()
        {
            @Override
            public void keyPressed(KeyEvent arg0)
            {
                System.out.print(((JTextComponent) arg0.getSource()).getText());
                if (arg0.getKeyCode() == KeyEvent.VK_ENTER)
                {
                    String JLabelText = ((JLabel) ((JPanel) ((JPanel) ((Component) arg0.getSource()).getParent()).getComponent(0)).getComponent(0)).getText();
                    int ansNum = (int)JLabelText.charAt(0)-95;
                    if (ansNum < 6)
                    {
                        Answer k = new Answer((Question) ((JTextArea) arg0.getSource()).getParent().getParent().getParent(), ansNum);
                        k.answer.grabFocus();
                        Main.mWindow.repaint();
                        Main.mWindow.validate();
                    }
                }

            }

            public void keyReleased(KeyEvent arg0) {}

            public void keyTyped(KeyEvent arg0) {}

        });

        doc = (AbstractDocument)answer.getDocument();
        doc.setDocumentFilter(new DefaultDocFilter());

        answer.setBackground(Color.PINK);

        add(answer);
        q.answerArea.add(this, index-1);
    }
}



public class Main
{

    public static Properties config;
    public static Locale currentLocale;
    public static ResourceBundle lang;

    public static JFrame mWindow;

    public static JMenuBar menu;
    public static JMenu menuFile, menuEdit;
    public static JMenuItem itmNew, itmClose, itmLoad, itmSave, itmSaveAs, itmExit, itmCut, itmCopy, itmPaste, itmProperties; 

    public static JDialog newDoc;
    public static JLabel newDocText1, newDocText2;
    public static JRadioButton questions, list;
    public static ButtonGroup newDocButtons;
    public static JButton newDocOk;
    public static Boolean firstSegment;

    public static JPanel workspace;
    public static JScrollPane scroll;
    public static ArrayList<Page> pages;


    public static void newDocumentForm()
    {
        //new document dialog
        mWindow.setEnabled(false);

        newDoc = new JDialog(mWindow, "newDoc");
        newDoc.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        newDoc.addWindowListener(new WindowListener ()
        {
            public void windowActivated(WindowEvent arg0) {}
            public void windowClosing(WindowEvent arg0)
            {
                mWindow.toFront();

                newDocText1 = null;
                newDocText2 = null;
                questions = null;
                list = null;
                newDocButtons = null;
                newDocOk = null;
                newDoc.dispose();

                mWindow.setEnabled(true);               
            }

            public void windowClosed(WindowEvent arg0) {}
            public void windowDeactivated(WindowEvent arg0) {}
            public void windowDeiconified(WindowEvent arg0) {}
            public void windowIconified(WindowEvent arg0) {}
            public void windowOpened(WindowEvent arg0) {}   
        });

        newDoc.setSize(400, 200);
        newDoc.setLocationRelativeTo(null);
        newDoc.setResizable(false);
        newDoc.setLayout(null);
        newDoc.setVisible(true);

        newDocText1 = new JLabel("newDocText1");
        newDocText1.setBounds(5, 0, 400, 20);

        newDocText2 = new JLabel("newDocText2");
        newDocText2.setBounds(5, 20, 400, 20);

        newDoc.add(newDocText1);
        newDoc.add(newDocText2);

        firstSegment = true;

        questions = new JRadioButton("questions");
        questions.setSelected(true);
        questions.setFocusPainted(false);
        questions.setBounds(10, 60, 400, 20);
        questions.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent arg0)
            {
                firstSegment = true;
            }
        });

        list = new JRadioButton("list");
        list.setFocusPainted(false);
        list.setBounds(10, 80, 400, 20);
        list.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent arg0)
            {
                firstSegment = false;
            }
        });

        newDoc.add(questions);
        newDoc.add(list);

        newDocButtons = new ButtonGroup();
        newDocButtons.add(questions);
        newDocButtons.add(list);

        newDocOk = new JButton("ok");
        newDocOk.addKeyListener(new KeyListener()
        {
            public void keyPressed(KeyEvent e)
            {
                if (e.getKeyCode() == KeyEvent.VK_ENTER)
                {
                    newDocOk.doClick();
                }
            }

            public void keyReleased(KeyEvent e) {}
            public void keyTyped(KeyEvent e) {}
        });

        newDocOk.setFocusPainted(false);
        newDocOk.setBounds(160, 120, 80, 40);
        newDocOk.setMnemonic(KeyEvent.VK_ACCEPT);
        newDocOk.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent arg0)
            {
                createNewDocument();
            }
        });

        newDoc.add(newDocOk);
        newDocOk.requestFocus();
    }

    public static void createNewDocument()
    {
        //dispose of new document dialog
        mWindow.toFront();

        newDocText1 = null;
        newDocText2 = null;
        questions = null;
        list = null;
        newDocButtons = null;
        newDocOk = null;
        newDoc.dispose();

        mWindow.setEnabled(true);

        //create document display               
        workspace = new JPanel();
        workspace.setLayout(new BoxLayout(workspace, BoxLayout.PAGE_AXIS));
        workspace.add(new Box.Filler(new Dimension(0, 40), new Dimension(0, 40), new Dimension(0, 40)));
        workspace.setBackground(Color.BLACK);

        scroll = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        scroll.getVerticalScrollBar().setUnitIncrement(20);
        scroll.setViewportView(workspace);

        pages = new ArrayList<Page>();

        Page p = new Page(workspace, 1);

        new Heading(true, p);

        Question q = new Question(p, 1, 1);

        new Answer(q, 1);

        mWindow.add(scroll, BorderLayout.CENTER);
        mWindow.repaint();
        mWindow.validate();

    }

    public static void main(String[] args) throws FileNotFoundException, IOException
    {   
        //create main window
        mWindow = new JFrame("title");
        mWindow.setSize(1000, 800);
        mWindow.setMinimumSize(new Dimension(1000, 800));
        mWindow.setLocationRelativeTo(null);
        mWindow.setLayout(new BorderLayout());
        mWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        mWindow.setVisible(true);

        //create menu bar
        menu = new JMenuBar();

        menuFile = new JMenu("file");
        menuEdit = new JMenu("edit");

        itmNew = new JMenuItem("new");
        itmNew.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, ActionEvent.CTRL_MASK));
        itmNew.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                newDocumentForm();
            }
        });

        itmClose = new JMenuItem("close");
        itmClose.setActionCommand("Close");
        itmClose.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_W, ActionEvent.CTRL_MASK));

        itmLoad = new JMenuItem("load");
        itmLoad.setActionCommand("Load");
        itmLoad.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_L, ActionEvent.CTRL_MASK));

        itmSave = new JMenuItem("save");
        itmSave.setActionCommand("Save");
        itmSave.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, ActionEvent.CTRL_MASK));

        itmSaveAs = new JMenuItem("saveAs");
        itmSaveAs.setActionCommand("SaveAs");
        itmExit = new JMenuItem("exit");
        itmExit.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                //Add confirmation window!
                System.exit(0);
            }
        });


        itmCut = new JMenuItem("cut");
        itmCut.setActionCommand("Cut");
        itmCut.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, ActionEvent.CTRL_MASK));

        itmCopy = new JMenuItem("copy");
        itmCopy.setActionCommand("Copy");
        itmCopy.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, ActionEvent.CTRL_MASK));

        itmPaste = new JMenuItem("paste");
        itmPaste.setActionCommand("Paste");
        itmPaste.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, ActionEvent.CTRL_MASK));

        itmProperties = new JMenuItem("properties");
        itmProperties.setActionCommand("properties");
        itmProperties.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_P, ActionEvent.CTRL_MASK));

        menuFile.add(itmNew);
        menuFile.add(itmClose);
        menuFile.addSeparator();
        menuFile.add(itmLoad);
        menuFile.addSeparator();
        menuFile.add(itmSave);
        menuFile.add(itmSaveAs);
        menuFile.addSeparator();
        menuFile.add(itmExit);

        menuEdit.add(itmCut);
        menuEdit.add(itmCopy);
        menuEdit.add(itmPaste);
        menuEdit.addSeparator();
        menuEdit.add(itmProperties);

        menu.add(menuFile);
        menu.add(menuEdit);

        //create actionListener for menus



        mWindow.add(menu, BorderLayout.NORTH);

        mWindow.repaint();
        mWindow.validate();
    }
}

Answer 1

Why don’t you assign String into DocumentFilter

str = str.replaceAll()?