This is my very first java swing application in school. We had to do a caesar coder.(http://en.wikipedia.org/wiki/Caesar_cipher)
It should know to crypt and decrypt and it should do it automaticly even if you don't press the button. (FocusListener)
It works like a dream, until I only have to do it with the "Code!" button. Then we had to add a DocumentListener, which I created, as shown below. It works if I use it only to crypt or only to decrypt. The problem occurs, when I add both JTextField to the same DocumentListener. I get an IllegalStateException with an "AWT-EventQueue-0" label. It calls the setText function two times, and the second one is fatal. I think it is because if I type a character to the first JTextField it is an insert, then when I set the content of the second JTextField with setText it is an insert too. Our prof said it can be fixed easily with a flag, but I'm failing. Can you help me please?
Application.java
package javaswinglabor;
public class Application {
public static void main(String[] args) {
CaesarFrame caesarFrame = new CaesarFrame();
}
}
CaesarProgram.java
package javaswinglabor;
public class CaesarProgram {
/**
* Caesar kodolo
* @param input
* @param offset
* @return kod
*/
static String caesarCoder(String input, char offset){
input = input.toUpperCase();
String kod="";
for(int i=0; i < input.length(); i++){
if(input.charAt(i) >= 'A' && input.charAt(i) <= 'Z' ) {
kod += (char)(65 + ((input.charAt(i) - 'A' + offset - 'A')%26) );
}
}
return kod;
}
/**
* Caesar dekodolo
* @param input
* @param offset
* @return kod
*/
static String caesarDecoder(String input, char offset){
input = input.toUpperCase();
String kod="";
for(int i=0; i < input.length(); i++){
if(input.charAt(i) >= 'A' && input.charAt(i) <= 'Z' ) {
kod += (char)(65 + (input.charAt(i) - offset + 26)%26 );
}
}
return kod;
}
}
CaesarFrame.java
package javaswinglabor;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
public class CaesarFrame extends JFrame{
//TOP JPanel
private JComboBox cb;
private JTextField t1;
private JButton b;
//DOWN JPanel
private JTextField t2;
//encrypt/decrypt
private boolean encrypt;
public CaesarFrame() throws HeadlessException {
super("SwingLab");
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setSize(400, 110);
this.setResizable(true);
this.setLayout(new GridLayout(2, 3));
JPanel pFelso = new JPanel(new FlowLayout(FlowLayout.LEFT));
JPanel pAlso = new JPanel(new FlowLayout(FlowLayout.LEFT));
this.add(pFelso);
this.add(pAlso);
//TOP Jpanel
cb = new JComboBox(fillObject());
t1 = new JTextField(20);
b = new JButton("Code!");
pFelso.add(cb);
pFelso.add(t1);
pFelso.add(b);
//DOWN JPanel
t2 = new JTextField(20);
//t2.setEditable(false);
pAlso.add(new JLabel("Output:"));
pAlso.add(t2);
//ButtonListener
OkButtonActionListener obl = new OkButtonActionListener();
b.addActionListener(obl);
//DocumentListeners
CoderDocumentFilter cdf = new CoderDocumentFilter();
DecoderDocumentFilter ddf = new DecoderDocumentFilter();
((AbstractDocument)(t1.getDocument())).setDocumentFilter((cdf));
((AbstractDocument)(t2.getDocument())).setDocumentFilter((ddf));
//InputFieldKeyListener ifkl = new InputFieldKeyListener();
//t1.addKeyListener(ifkl);
//SpecialDocumentListener t1_dl = new SpecialDocumentListener();
//t1.getDocument().addDocumentListener(t1_dl);
//t2.getDocument().addDocumentListener(t1_dl);
//FocusListener
JTextFieldFocusListener jtfl = new JTextFieldFocusListener();
t1.addFocusListener(jtfl);
t2.addFocusListener(jtfl);
this.pack();
this.setVisible(true);
}
private void Coder(){
Character c = (Character)cb.getSelectedItem();
t2.setText( CaesarProgram.caesarCoder(t1.getText(), c.charValue()) );
}
private void Decoder(){
Character c = (Character)cb.getSelectedItem();
t1.setText( CaesarProgram.caesarDecoder(t2.getText(), c.charValue()) );
}
private class CoderDocumentFilter extends DocumentFilter{
@Override public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
super.insertString(fb, offset, text.toUpperCase(), attr);
if (encrypt) {Coder();}
}
@Override public void replace (DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attr) throws BadLocationException {
super.replace(fb, offset, length, text.toUpperCase(), attr);
if (encrypt) {Coder();}
}
@Override public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException{
super.remove(fb, offset, length);
if (encrypt) {Coder();}
}
}
private class DecoderDocumentFilter extends DocumentFilter{
@Override public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
super.insertString(fb, offset, text.toUpperCase(), attr);
if (!encrypt) {Decoder();}
}
@Override public void replace (DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attr) throws BadLocationException {
super.replace(fb, offset, length, text.toUpperCase(), attr);
if (!encrypt) {Decoder();}
}
@Override public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException{
super.remove(fb, offset, length);
if (!encrypt) {Decoder();}
}
}
/**
* Egy 26-elemu Object tombot tolt fel az angol ABC nagybetuivel.
* @return object[]
*/
private static Object[] fillObject() {
Object[] object = new Object[26];
for(int i=0; i < 26; i++){
object[i] = (char)(i+65);
}
return object;
}
//Button listener
private class OkButtonActionListener implements ActionListener{
@Override
public void actionPerformed(ActionEvent ae) {
if(encrypt){Coder();}
else{Decoder();}
}
}
//FocusListener
private class JTextFieldFocusListener implements FocusListener {
@Override public void focusGained(FocusEvent fe) {
if(t1.isFocusOwner()) {encrypt = true;}
else if(t2.isFocusOwner()){encrypt = false;}
}
@Override public void focusLost(FocusEvent fe) {}
}
//Previous task
/*
private class InputFieldKeyListener extends KeyAdapter {
@Override public void keyPressed(KeyEvent ke) {
super.keyPressed(ke);
Character c = (Character)cb.getSelectedItem();
String s = String.valueOf(ke.getKeyChar());
t2.setText(t2.getText() + CaesarProgram.caesarCoder(s, c.charValue()) );
}
}
*/
}
I solved the problem, thank you all, for your useful help. I'm sure it isn't the most elegant or the fastest solution, but it works finally. I would be glad, if somebody would like to make it more efficent or easier/cleaner.
From How to Write a Document Listener:
Document listeners should not modify the contents of the document; The change is already complete by the time the listener is notified of the change.
To fix this problem, use a DocumentFilter rather than a DocumentListener.
See this example Implementing a Document Filter