Get a key from JTextArea

Question

All I want to do, If I'm pressing '{' this key in JtextArea.automatically '}' this will be print also.

 if(evt.KEY_PRESSED == '{')

            System.out.print("}");

is this is okay??

Saval

Not quite sure what you are trying to achieve. Have you tried this yet? What exactly is the problem? – Controvert

@Saval : What you trying to achieve must be done inside the keyReleased() method, not keyPressed(), something like this public void keyReleased(KeyEvent ke){if (ke.getKeyCode() == 91){System.out.println(KeyEvent.VK_BRACELEFT);int len = tarea.getDocument().getLength();tarea.append("}");}}. Then only you will get your output. Moreover what "@mKorbel" had told you that's the new way that goes with Swing. KeyListener is for awt not for Swing. – Threatt

Answer 1

for listening changes into JTextComponent is there DocumentListener, if you have to need control over inputed Char, sings, whitespace chars or word(s) you have to implements DocumentFilter

notice for Chars reservated by programing language(s) you have to use double escapes,

\\( instead of (

or

\\{ instead of {

otherwise you get

Exception in thread "AWT-EventQueue-0" java.util.regex.PatternSyntaxException: 
Illegal repetition

for example

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

public class TextAreaTest extends JFrame {

    private static final long serialVersionUID = 1L;
    private JTextArea textArea;

    public TextAreaTest() {
        textArea = new JTextArea();
        textArea.setPreferredSize(new Dimension(60, 32));
        textArea.setOpaque(true);
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        ((AbstractDocument) textArea.getDocument()).setDocumentFilter(new DocumentFilter() {

            @Override
            public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
                string = string.replaceAll("\\{", "\\{}");
                super.insertString(fb, offset, string, attr);
            }

            @Override
            public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
                text = text.replaceAll("\\{", "\\{}");
                //TODO must do something here
                super.replace(fb, offset, length, text, attrs);
            }
        });

        textArea.getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void changedUpdate(DocumentEvent e) {
                update(e);
            }

            @Override
            public void insertUpdate(DocumentEvent e) {
                update(e);
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                update(e);
            }

            private void update(DocumentEvent e) {
                List<String> lines = getLines(textArea);
                String lastLine = lines.get(lines.size() - 1);
                int tabbedTextWidth = Utilities.getTabbedTextWidth(new Segment(
                        lastLine.toCharArray(), 0, lastLine.length()), textArea.getFontMetrics(textArea.getFont()), 0, null, 0);
                int lineHeight = getLineHeight(textArea);
                if (lines.size() * lineHeight > textArea.getHeight() || tabbedTextWidth > textArea.getWidth()) {
                    System.out.println("Too big! Should refuse the update!");
                }
            }
        });

        getContentPane().add(textArea);
    }

    private static List<String> getLines(JTextArea textArea) {
        int lineHeight = getLineHeight(textArea);
        List<String> list = new ArrayList<String>();
        for (int num = 0;; num++) {
            int i = textArea.viewToModel(new Point(0, num * lineHeight));
            int j = textArea.viewToModel(new Point(0, (num + 1) * lineHeight));
            if (i == 0 && j == 0) {
                continue;
            }
            if (textArea.getDocument().getLength() == i && i == j) {
                break;
            }
            String s = removeTrailingNewLine(textArea.getText().substring(i, j));
            list.add(s);
            //System.out.println(i + " " + j + " = " + s);
        }
        return list;
    }

    private static int getLineHeight(JTextArea textArea) {
        return textArea.getFontMetrics(textArea.getFont()).getHeight();
    }

    private static String removeTrailingNewLine(String s) {
        if (s.endsWith("\n")) {
            return s.substring(0, s.length() - 1);
        } else {
            return s;
        }
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                TextAreaTest test = new TextAreaTest();
                test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                test.pack();
                test.setVisible(true);
            }
        });
    }
}

Sienna

Too complex, but got the idea inside the DocumentFilter class. +1 for this :-) – Threatt

hmmm I think there isn't another, easiest and faster way – Sienna

Answer 2

You need KeyBinding http://tips4java.wordpress.com/2008/10/10/key-bindings/ and http://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html

Refugiorefulgence

Answer 3

I think this is what you are looking for

if(evt.getID() == evt.KEY_PRESSED) {

    if(evt.getKeyChar() == '{') {
        System.out.print("}");
    }
}

Tested and works

Libertinage