如何调试导致错误的 Swing 按钮？

Question

我正在进行计算机研究控制评估。这是一个加密/解密程序。但是，我正在尝试听一个名为 Gui_Maker 的类中的一个按钮，它制作 GUI 和所有摆动元素。然后，我想将信息传递给另一个名为 Computerscience 的类中的方法。但是每次我按下按钮时都会出错。

我在 Java 方面一点也不精通，如果任何解释给出了我应该放入我的程序中的任何代码，并且用外行的术语解释，这将有所帮助。

这是我的代码：

package computerscience;

import java.awt.EventQueue;

import javax.swing.JFrame;

import java.awt.GridBagLayout;

import javax.swing.JButton;

import java.awt.GridBagConstraints;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JLabel;
import javax.swing.JTextArea;

public class Gui_Maker implements ActionListener {

Computerscience computerscience = new Computerscience();

JButton btnEncrypt = new JButton("Encrypt");
JButton btnDecrypt = new JButton("Decrypt");
JButton btnOpen = new JButton("Open");

protected JLabel lblEnterYourMessage;
protected JLabel lblEnterYourOffset;
protected JTextArea txtrMessage;
protected JTextArea txtrOffset;
private JFrame frame;

boolean test;


/**
 * Launch the application.
 */
public static void main(String[] args) {

    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Gui_Maker window = new Gui_Maker();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the application.
 */
public Gui_Maker() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    btnEncrypt.addActionListener(this); 
    btnDecrypt.addActionListener(this);
    btnOpen.addActionListener(this);

    frame = new JFrame();
    frame.setBounds(100, 100, 475, 240);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    GridBagLayout gridBagLayout = new GridBagLayout();
    gridBagLayout.columnWidths = new int[] { 0, 0, 0 };
    gridBagLayout.rowHeights = new int[] { 0, 0, 0, 0 };
    gridBagLayout.columnWeights = new double[] { 1.0, 0.0, Double.MIN_VALUE };
    gridBagLayout.rowWeights = new double[] { 1.0, 1.0, 1.0, 1.0 };
    frame.getContentPane().setLayout(gridBagLayout);

    JLabel lblEnterYourMessage = new JLabel("Enter your message here");
    GridBagConstraints gbc_lblEnterYourMessage = new GridBagConstraints();
    gbc_lblEnterYourMessage.anchor = GridBagConstraints.SOUTH;
    gbc_lblEnterYourMessage.insets = new Insets(0, 0, 5, 5);
    gbc_lblEnterYourMessage.gridx = 0;
    gbc_lblEnterYourMessage.gridy = 0;
    frame.getContentPane()
            .add(lblEnterYourMessage, gbc_lblEnterYourMessage);

    JTextArea txtrMessage = new JTextArea();
    txtrMessage.setText("Message");
    GridBagConstraints gbc_txtrMessage = new GridBagConstraints();
    gbc_txtrMessage.insets = new Insets(0, 0, 5, 5);
    gbc_txtrMessage.fill = GridBagConstraints.BOTH;
    gbc_txtrMessage.gridx = 0;
    gbc_txtrMessage.gridy = 1;
    frame.getContentPane().add(txtrMessage, gbc_txtrMessage);

    GridBagConstraints gbc_btnEncrypt = new GridBagConstraints();
    gbc_btnEncrypt.fill = GridBagConstraints.VERTICAL;
    gbc_btnEncrypt.insets = new Insets(0, 0, 5, 0);
    gbc_btnEncrypt.gridx = 1;
    gbc_btnEncrypt.gridy = 1;
    frame.getContentPane().add(btnEncrypt, gbc_btnEncrypt);

    JLabel lblEnterYourOffset = new JLabel("Enter your offset here");
    GridBagConstraints gbc_lblEnterYourOffset = new GridBagConstraints();
    gbc_lblEnterYourOffset.anchor = GridBagConstraints.SOUTH;
    gbc_lblEnterYourOffset.insets = new Insets(0, 0, 5, 5);
    gbc_lblEnterYourOffset.gridx = 0;
    gbc_lblEnterYourOffset.gridy = 2;
    frame.getContentPane().add(lblEnterYourOffset, gbc_lblEnterYourOffset);

    GridBagConstraints gbc_btnDecrypt = new GridBagConstraints();
    gbc_btnDecrypt.fill = GridBagConstraints.VERTICAL;
    gbc_btnDecrypt.insets = new Insets(0, 0, 5, 0);
    gbc_btnDecrypt.gridx = 1;
    gbc_btnDecrypt.gridy = 2;
    frame.getContentPane().add(btnDecrypt, gbc_btnDecrypt);

    JTextArea txtrOffset = new JTextArea();
    txtrOffset.setText("Offset");
    GridBagConstraints gbc_txtrOffset = new GridBagConstraints();
    gbc_txtrOffset.insets = new Insets(0, 0, 0, 5);
    gbc_txtrOffset.fill = GridBagConstraints.BOTH;
    gbc_txtrOffset.gridx = 0;
    gbc_txtrOffset.gridy = 3;
    frame.getContentPane().add(txtrOffset, gbc_txtrOffset);

    GridBagConstraints gbc_btnOpen = new GridBagConstraints();
    gbc_btnOpen.fill = GridBagConstraints.VERTICAL;
    gbc_btnOpen.gridx = 1;
    gbc_btnOpen.gridy = 3;
    frame.getContentPane().add(btnOpen, gbc_btnOpen);

}

public void actionPerformed(ActionEvent e) {

    if (e.getSource() == btnEncrypt) {
        String input_text;
        int input_offset;
        test = true;
        input_text = txtrMessage.getText();
        input_offset = Integer.parseInt(txtrOffset.getText());
        computerscience.encrypt(input_text, input_offset, test);
    }
    if (e.getSource() == btnDecrypt) {
        String input_text;
        int input_offset;
        test = false;
        input_text = txtrMessage.getText();
        input_offset = Integer.parseInt(txtrOffset.getText());
        computerscience.decrypt(input_text, input_offset, test);
    }
    if (e.getSource() == btnOpen) {

    }
}

}

Answer 1

这些是您班级中的字段：

protected JTextArea txtrMessage;
protected JTextArea txtrOffset;

在这里，您在方法中本地重新创建对象

JTextArea txtrMessage = new JTextArea();
//...  
JTextArea txtrOffset = new JTextArea();

在另一种方法中，您可以访问未初始化的字段：

input_text = txtrMessage.getText();
input_offset = Integer.parseInt(txtrOffset.getText());

在 init 方法的代码中省略类型。

txtrMessage = new JTextArea();
//...  
txtrOffset = new JTextArea();

对于其他一些 JComponents 也是如此，尽管这些并没有什么坏处：

lblEnterYourMessage = ...
lblEnterYourOffset = ...