java - 使用 DocumentListener 修改多个 JTextField

Question

这是我在学校的第一个 java swing 应用程序。我们不得不做一个凯撒编码器。 (http://en.wikipedia.org/wiki/Caesar_cipher)

它应该知道加密和解密，即使您没有按下按钮，它也应该自动执行。 (焦点监听器)

它像做梦一样工作，直到我只需要用“代码”来做它!按钮。然后我们必须添加一个我创建的 DocumentListener，如下所示。如果我仅将它用于加密或仅用于解密，它就可以工作。当我将两个 JTextField 添加到同一个 DocumentListener 时，就会出现问题。我收到带有“AWT-EventQueue-0”标签的 IllegalStateException。它调用了 setText 函数两次，第二次是致命的。我认为这是因为如果我在第一个 JTextField 中键入一个字符，它就是一个插入，然后当我使用 setText 设置第二个 JTextField 的内容时，它也是一个插入。我们的教授说可以用旗帜轻松修复它，但我失败了。你能帮帮我吗？

应用程序.java

    package javaswinglabor;

    public class Application {
        public static void main(String[] args) {
        CaesarFrame caesarFrame = new CaesarFrame();
        }
    }

凯撒程序.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;
    }
}

凯撒框架.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()) );
    }
    }
    */
}

我解决了这个问题，谢谢大家的帮助。我敢肯定它不是最优雅或最快的解决方案，但它最终会起作用。如果有人想让它更高效或更容易/更清洁，我会很高兴。

Answer 1

来自 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.

要解决此问题，请使用 DocumentFilter 而不是 DocumentListener。

查看此示例 Implementing a Document Filter