How to make one JTextArea change when another is e

2019-09-02 22:49发布

站内文章 / Java
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问题:

import javax.swing.*;
import java.awt.event.*;
import javax.swing.text.DefaultFormatter;
import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.Document;


public class CipherGUI{

    public static void main(String args[]){
        try {
            UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
        } catch (Exception e) {}
        JFrame cipherGUIFrame = new CipherGUIFrame();
        cipherGUIFrame.setVisible(true);
    }
}

class CipherGUIFrame extends JFrame {

    public boolean decrypt=true;

  public CipherGUIFrame() {
    super("Caesar Cipher GUI");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(400, 600);

    JTextArea area1 = new JTextArea();
    JTextArea area2 = new JTextArea();
    JSpinner myspinner=new JSpinner();
    JPanel mainframe = new JPanel();
    JToggleButton mybutton=new JToggleButton("ENCRYPT");
    mainframe.setLayout(new BoxLayout(mainframe, BoxLayout.Y_AXIS));
    JPanel p1 = new JPanel();
    JPanel p2 = new JPanel();
    JPanel p3 = new JPanel();
    p1.setLayout(new BoxLayout(p1, BoxLayout.X_AXIS));
    p2.setLayout(new BoxLayout(p2, BoxLayout.X_AXIS));
    p1.setBorder(BorderFactory.createTitledBorder("Cleartext"));
    p2.setBorder(BorderFactory.createTitledBorder("KEY"));
    p3.setLayout(new BoxLayout(p3, BoxLayout.X_AXIS));
    p3.setBorder(BorderFactory.createTitledBorder("Ciphertext"));
    p1.add(area1);
    p2.add(myspinner);
    p2.add(mybutton);
    p3.add(area2);
    mainframe.add(p1);
    mainframe.add(p2);
    mainframe.add(p3);
    this.add(mainframe);

    ActionListener togglelistener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        AbstractButton abstractButton = (AbstractButton) actionEvent.getSource();
        boolean selected = abstractButton.getModel().isSelected();
        decrypt=selected;
        System.out.println("Selected (True or False?): " + selected + "\n");
      }
    };
    mybutton.addActionListener(togglelistener);


    //the following chunk of code modifies the component to update when spinner is changed automatically
    JComponent comp = myspinner.getEditor();
    JFormattedTextField field = (JFormattedTextField) comp.getComponent(0);
    DefaultFormatter formatter = (DefaultFormatter) field.getFormatter();
    formatter.setCommitsOnValidEdit(true);
    myspinner.addChangeListener(new ChangeListener() {

        @Override
        public void stateChanged(ChangeEvent e) {
            System.out.println("Key spinner changed to: " + myspinner.getValue());
        }
    });


    DocumentListener documentListener = new DocumentListener() {
      public void changedUpdate(DocumentEvent documentEvent) {
        printIt(documentEvent);
      }
      public void insertUpdate(DocumentEvent documentEvent) {
        printIt(documentEvent);
      }
      public void removeUpdate(DocumentEvent documentEvent) {
        printIt(documentEvent);
      }
      private void printIt(DocumentEvent documentEvent) {
        DocumentEvent.EventType type = documentEvent.getType();
        String typeString = null;
        if (type.equals(DocumentEvent.EventType.CHANGE)) {
          typeString = "(CHANGED KEY) ";
        }  else if (type.equals(DocumentEvent.EventType.INSERT)) {
          typeString = "(PRESSED KEY) ";
        }  else if (type.equals(DocumentEvent.EventType.REMOVE)) {
          typeString = "(DELETED KEY) ";
        }
        System.out.print("Type : " + typeString);
        Document source = documentEvent.getDocument();
        int length = source.getLength();
        System.out.println("Current size: " + length);
        String contents=source.getText(0, length);
        System.out.println(contents);
      }
    };
    area1.getDocument().addDocumentListener(documentListener);
    area2.getDocument().addDocumentListener(documentListener);
  }

  public String decipher(String istring, int key){
      String decrypted = "";

        for(int i=0; i<istring.length(); i++){

            int c = istring.charAt(i);

            if (Character.isUpperCase(c)){
                c = c - (key % 26);
                if (c < 'A')
                c = c + 26;
            }

            else if (Character.isLowerCase(c)){
                c = c - (key % 26);
                if (c < 'a')
                c = c + 26;
            }

            decrypted += (char) c;
        }

      return(decrypted);
  }

  public String encipher(String istring, int key){
      String encrypted = "";
        for(int i=0; i<istring.length(); i++){

            int c = istring.charAt(i);

            if (Character.isUpperCase(c)){
                c = c - (key % 26);
                if (c < 'A')
                c = c + 26;
            }

            else if (Character.isLowerCase(c)){
                c = c - (key % 26);
                if (c < 'a')
                c = c + 26;
            }

            encrypted += (char) c;
        }

      return (encrypted);
  }
}

That is my current code. As you can see, I use two text areas - one for encryption, the other for decryption. I want one to update as soon as the other's updates and vice versa. The line I am having trouble with (and stuck here debugging) is the 

    String contents=source.getText(0, length);

line. I am trying to make it so that I can read the contents of the text area whenever it is changed to be able to send it through the encrypt (or decrypt) methods and output it to the other text area (which I know how to do). The thing I am having trouble with is gettings the contents of the TextArea when it changes. Any ideas? (Disregard the KEY CHANGED outputs, those were for testing...)

回答1:

Documents don't like been modified while they are been updated, they will throw exceptions if they catch you doing this.

What you should be using is a DocumentFilter which can alter the text before it is applied to the Document, this is a great way to introduce the encryption process.

I would consider changing your process slightly. Instead of allowing the user to edit either JTextArea, only allow them to edit the first and have a JCheckBox to signify in which direction they want to go (encrypt/decrypt), this would greatly simplifier the process...

The following example uses a DocumentFilter to encrypt the text that is been input into, but it uses a DocumentListener, applied to the area1 to update the Document of area2, because we're not modifying the Document which triggered the event, this should be, reasonably, safe...

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.AbstractButton;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JComponent;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSpinner;
import javax.swing.JTextArea;
import javax.swing.JToggleButton;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultFormatter;
import javax.swing.text.Document;
import javax.swing.text.DocumentFilter;
import javax.swing.text.html.HTML;

public class CipherGUI {

    public static void main(String[] args) {
        new CipherGUI();
    }

    public CipherGUI() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame cipherGUIFrame = new CipherGUIFrame();
                cipherGUIFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                cipherGUIFrame.pack();
                cipherGUIFrame.setLocationRelativeTo(null);
                cipherGUIFrame.setVisible(true);
            }
        });
    }

    class CipherGUIFrame extends JFrame {

        public boolean decrypt = true;

        public CipherGUIFrame() {
            super("Caesar Cipher GUI");
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            setSize(400, 600);

            JTextArea area1 = new JTextArea();
            JTextArea area2 = new JTextArea();
            JSpinner myspinner = new JSpinner();
            JPanel mainframe = new JPanel();
            JToggleButton mybutton = new JToggleButton("ENCRYPT");
            mainframe.setLayout(new BoxLayout(mainframe, BoxLayout.Y_AXIS));
            JPanel p1 = new JPanel();
            JPanel p2 = new JPanel();
            JPanel p3 = new JPanel();
            p1.setLayout(new BoxLayout(p1, BoxLayout.X_AXIS));
            p2.setLayout(new BoxLayout(p2, BoxLayout.X_AXIS));
            p1.setBorder(BorderFactory.createTitledBorder("Cleartext"));
            p2.setBorder(BorderFactory.createTitledBorder("KEY"));
            p3.setLayout(new BoxLayout(p3, BoxLayout.X_AXIS));
            p3.setBorder(BorderFactory.createTitledBorder("Ciphertext"));
            p1.add(area1);
            p2.add(myspinner);
            p2.add(mybutton);
            p3.add(area2);
            mainframe.add(p1);
            mainframe.add(p2);
            mainframe.add(p3);
            this.add(mainframe);

            ActionListener togglelistener = new ActionListener() {
                public void actionPerformed(ActionEvent actionEvent) {
                    AbstractButton abstractButton = (AbstractButton) actionEvent.getSource();
                    boolean selected = abstractButton.getModel().isSelected();
                    decrypt = selected;
                    System.out.println("Selected (True or False?): " + selected + "\n");
                }
            };
            mybutton.addActionListener(togglelistener);

            //the following chunk of code modifies the component to update when spinner is changed automatically
            JComponent comp = myspinner.getEditor();
            JFormattedTextField field = (JFormattedTextField) comp.getComponent(0);
            DefaultFormatter formatter = (DefaultFormatter) field.getFormatter();
            formatter.setCommitsOnValidEdit(true);
            myspinner.addChangeListener(new ChangeListener() {

                @Override
                public void stateChanged(ChangeEvent e) {
                    System.out.println("Key spinner changed to: " + myspinner.getValue());
                    EncryptFilter filter = (EncryptFilter) ((AbstractDocument) area2.getDocument()).getDocumentFilter();
                    filter.setKey((int)myspinner.getValue());
                    area2.setText(area1.getText());
                }
            });

            ((AbstractDocument) area2.getDocument()).setDocumentFilter(new EncryptFilter(0));

            area1.getDocument().addDocumentListener(new DocumentListener() {
                @Override
                public void insertUpdate(DocumentEvent e) {
                    try {
                        Document doc = e.getDocument();
                        String text = doc.getText(e.getOffset(), e.getLength());
                        Document encryptDoc = area2.getDocument();
                        encryptDoc.insertString(e.getOffset(), text, null);
                    } catch (BadLocationException exp) {
                        exp.printStackTrace();
                    }
                }

                @Override
                public void removeUpdate(DocumentEvent e) {
                    try {
                        Document doc = e.getDocument();
                        Document encryptDoc = area2.getDocument();
                        encryptDoc.remove(e.getOffset(), e.getLength());
                    } catch (BadLocationException exp) {
                        exp.printStackTrace();
                    }
                }

                @Override
                public void changedUpdate(DocumentEvent e) {
                    System.out.println("Changed");
                }
            });
        }
    }

    public static String decipher(String istring, int key) {
        String decrypted = "";

        for (int i = 0; i < istring.length(); i++) {

            int c = istring.charAt(i);

            if (Character.isUpperCase(c)) {
                c = c - (key % 26);
                if (c < 'A') {
                    c = c + 26;
                }
            } else if (Character.isLowerCase(c)) {
                c = c - (key % 26);
                if (c < 'a') {
                    c = c + 26;
                }
            }

            decrypted += (char) c;
        }

        return (decrypted);
    }

    public static String encipher(String istring, int key) {
        String encrypted = "";
        for (int i = 0; i < istring.length(); i++) {

            int c = istring.charAt(i);

            if (Character.isUpperCase(c)) {
                c = c - (key % 26);
                if (c < 'A') {
                    c = c + 26;
                }
            } else if (Character.isLowerCase(c)) {
                c = c - (key % 26);
                if (c < 'a') {
                    c = c + 26;
                }
            }

            encrypted += (char) c;
        }

        return (encrypted);
    }

    public class EncryptFilter extends DocumentFilter {

        private int key;

        public EncryptFilter(int key) {
            this.key = key;
        }

        public void setKey(int key) {
            this.key = key;
        }

        @Override
        public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
            System.out.println("Insert");
            text = encipher(text, key);
            super.insertString(fb, offset, text, attr);
        }

        @Override
        public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
            System.out.println("Remove");
            super.remove(fb, offset, length);
        }



        @Override
        public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {

            text = encipher(text, key);
            super.replace(fb, offset, length, text, attrs);
        }

    }
}

Take a closer look at Implementing a Document Filter and DocumentFilter Examples for more details



标签： java jtextarea documentlistener
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