Java documentlistener - 输入后程序停止工作

Question

您好，我的文档监听器有问题。将值插入文本字段后，程序停止工作。该程序应将第一行文本字段与第二行文本字段进行异或，并将结果放入第三行文本字段

package opa.beta1;

import java.awt.BorderLayout;
import java.math.BigInteger;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class TextFieldEvent {

    JTextField arrayIV[] = new JTextField[8];
    JTextField plaintextArray[] = new JTextField[8];
    JTextField ciphertextArray[] = new JTextField[8];
    JFrame frame = new JFrame("OPA");
    JPanel panel1 = new JPanel();
    JPanel panel2 = new JPanel();
    JPanel panel3 = new JPanel();

    public void setJPanel(JTextField array[], JPanel container, String s) {
        for (int i = 0; i < 8; i++) {
            array[i] = new JTextField(s, 4);
            array[i].getDocument().addDocumentListener(new DocumentListener() {
                @Override
                public void insertUpdate(DocumentEvent de) {
                    setCiphertext();
                }

                @Override
                public void removeUpdate(DocumentEvent de) {
                    setCiphertext();
                }

                @Override
                public void changedUpdate(DocumentEvent de) {
                    setCiphertext();
                }
            });
            container.add(array[i]);
        }
    }

    public String setXORText(JTextField textfield1, JTextField textfield2) {
        String okno1, okno2;
        okno1 = textfield1.getText();
        okno2 = textfield2.getText();
        if (okno1.equals("")) {
            return okno2;
        }
        BigInteger pom1 = new BigInteger(okno1, 16);
        if (okno2.equals("")) {
            return okno1;
        }
        BigInteger pom2 = new BigInteger(okno2, 16);
        BigInteger res = pom1.xor(pom2);
        String s = res.toString(16);
        return s;
    }

    public String setXORText(JTextField pole1[], JTextField pole2[], int i) {

        String okno1 = pole1[i].getText();
        String okno2 = pole2[i].getText();
        if (okno1.equals("")) {
            return pole2[i].getText();
        }
        BigInteger pom1 = new BigInteger(okno1, 16);
        if (okno2.equals("")) {
            return pole1[i].getText();
        }
        BigInteger pom2 = new BigInteger(okno2, 16);
        BigInteger res = pom1.xor(pom2);
        String s = res.toString(16);
        return s;
    }

    public void setCiphertext() {
        //textfield3.setText(setXORText(textfield1, textfield2));
        for (int i = 0; i < 8; i++) {
            ciphertextArray[i].setText(setXORText(arrayIV, plaintextArray, i));
        }
    }

    public TextFieldEvent() {
        setJPanel(arrayIV, panel1, "1a");
        setJPanel(plaintextArray, panel2, "1b");
        setJPanel(ciphertextArray, panel3, "1");

        frame.add(panel1, BorderLayout.NORTH);
        frame.add(panel2, BorderLayout.CENTER);
        frame.add(panel3, BorderLayout.SOUTH);

        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
        frame.setSize(675, 275);
        frame.setResizable(false);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TextFieldEvent();
            }
        });

    }
}

堆栈跟踪

Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Attempt to mutate in notification at javax.swing.text.AbstractDocument.writeLock(AbstractDocument.java:1338) at javax.swing.text.AbstractDocument.replace(AbstractDocument.java:659) at javax.swing.text.JTextComponent.setText(JTextComponent.java:1718) at opa.beta1.TextFieldEvent.setCiphertext(TextFieldEvent.java:82) at opa.beta1.TextFieldEvent$1.removeUpdate(TextFieldEvent.java:33)

Answer 1

这一行

setJPanel(ciphertextArray, panel3, "1");

还向 ciphertextArray TextField 的每个元素添加一个 DocumentListener。因此，每次密文 TextField 的值发生变化时，都会调用方法 setCipherText()。

这会导致以下序列:

1. 您在 arrayIV 或 plainTextArray 的 TextField 之一中输入新值
2. setCipherText() 被调用
3. setCipherText() 更改密文的值 TextField
4. setCipherText() 再次被调用(解释见上文)。返回2。

这就是为什么你会得到IllegalStateException。

因此，解决方案是不要将 DocumentListener 添加到 ciphertextArray 中的 TextFields。

解决方案可以按如下方式实现:

public void setJPanel(JTextField array[], JPanel container, String s, boolean docListener) {
    for (int i = 0; i < 8; i++) {
        array[i] = new JTextField(s, 4);
        if (docListener) {
            array[i].getDocument().addDocumentListener(new DocumentListener() {
                @Override
                public void insertUpdate(DocumentEvent de) {
                    setCiphertext();
                }

                @Override
                public void removeUpdate(DocumentEvent de) {
                    setCiphertext();
                }

                @Override
                public void changedUpdate(DocumentEvent de) {
                    setCiphertext();
                }
            });
        }
        container.add(array[i]);
    }
}

[...]

    setJPanel(arrayIV, panel1, "1a", true);
    setJPanel(plaintextArray, panel2, "1b", true);
    setJPanel(ciphertextArray, panel3, "1", false);