Java Swing GUI尝试/捕获块

Question

我只是在学习Java异常处理和Java。我制作了一个Swing
GUI，用户将在两个字段中输入整数，然后单击带有算术函数的单选按钮，答案将出现在第三个文本字段中。我想包含一个try /
catch块，以在用户将前两个字段之一留为空白或输入除整数以外的内容时捕获异常，以及如果用户尝试将其除以零则输入第二个catch。该窗体可以正常工作，但是不会捕获错误，只能返回堆栈跟踪并使程序崩溃。我感觉我只是在错误的位置放置了try
/ catch块，但随着移动的越多，事情越糟。有人可以指出我出了问题吗？

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ButtonGroup;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JRadioButton;
import javax.swing.JTextField;

import javax.swing.WindowConstants;
import javax.swing.SwingUtilities;

public class Main extends javax.swing.JFrame {
    private JTextField aTextField;
    private JRadioButton dRadioButton;
    private ButtonGroup buttonGroup;
    private JLabel aLabel;
    private JRadioButton cRadioButton;
    private JRadioButton bRadioButton;
    private JRadioButton aRadioButton;
    private JTextField cTextField;
    private JTextField bTextField;

    /**
     * Auto-generated main method to display this JFrame
     */
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                Main inst = new Main();
                inst.setLocationRelativeTo(null);
                inst.setVisible(true);
            }
        });
    }

    public Main() {
        super();
        initGUI();
    }

    private void initGUI() {
        try {
            setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
            getContentPane().setLayout(null);
            {
                aTextField = new JTextField();
                getContentPane().add(aTextField);
                aTextField.setBounds(12, 49, 62, 30);
            }
            {
                bTextField = new JTextField();
                getContentPane().add(bTextField);
                bTextField.setBounds(178, 49, 62, 31);
            }
            {
                cTextField = new JTextField();
                getContentPane().add(cTextField);
                cTextField.setBounds(297, 49, 62, 30);
            }
            {
                aRadioButton = new JRadioButton();
                getContentPane().add(aRadioButton);
                aRadioButton.setText("+");
                aRadioButton.setBounds(91, 18, 43, 20);
                aRadioButton.setFont(new java.awt.Font("Segoe UI", 1, 16));
                aRadioButton.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent evt) {
                        aRadioButtonActionPerformed(evt);
                    }
                });
                getButtonGroup().add(aRadioButton);
            }
            {
                bRadioButton = new JRadioButton();
                getContentPane().add(bRadioButton);
                bRadioButton.setText("-");
                bRadioButton.setBounds(91, 53, 43, 20);
                bRadioButton.setFont(new java.awt.Font("Segoe UI", 1, 16));
                bRadioButton.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent evt) {
                        bRadioButtonActionPerformed(evt);
                    }
                });
                getButtonGroup().add(bRadioButton);
            }
            {
                cRadioButton = new JRadioButton();
                getContentPane().add(cRadioButton);
                cRadioButton.setText("*");
                cRadioButton.setBounds(91, 99, 43, 20);
                cRadioButton.setFont(new java.awt.Font("Segoe UI", 1, 16));
                cRadioButton.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent evt) {
                        cRadioButtonActionPerformed(evt);
                    }
                });
                getButtonGroup().add(cRadioButton);
            }
            {
                dRadioButton = new JRadioButton();
                getContentPane().add(dRadioButton);
                getContentPane().add(getALabel());
                dRadioButton.setText("/");
                dRadioButton.setBounds(91, 140, 46, 20);
                dRadioButton.setFont(new java.awt.Font("Segoe UI", 1, 16));
                dRadioButton.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent evt) {
                        dRadioButtonActionPerformed(evt);
                    }
                });
                getButtonGroup().add(dRadioButton);
            }
            pack();
            setSize(400, 300);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null,
                    "Error: You must enter an integer");

        } catch (ArithmeticException e) {
            JOptionPane.showMessageDialog(null,
                    "Error: You cannot divide by zero");
        }
    }

    private ButtonGroup getButtonGroup() {
        if (buttonGroup == null) {
            buttonGroup = new ButtonGroup();
        }
        return buttonGroup;
    }

    private JLabel getALabel() {
        if (aLabel == null) {
            aLabel = new JLabel();
            aLabel.setText("=");
            aLabel.setBounds(249, 56, 30, 16);
            aLabel.setFont(new java.awt.Font("Segoe UI", 1, 16));
        }
        return aLabel;
    }

    private void aRadioButtonActionPerformed(ActionEvent evt) {
        String a = aTextField.getText();
        int i = Integer.parseInt(a);
        String b = bTextField.getText();
        int j = Integer.parseInt(b);
        int k = i + j;
        cTextField.setText(Integer.toString(k));
    }

    private void bRadioButtonActionPerformed(ActionEvent evt) {
        String a = aTextField.getText();
        int i = Integer.parseInt(a);
        String b = bTextField.getText();
        int j = Integer.parseInt(b);
        int k = i - j;
        cTextField.setText(Integer.toString(k));
    }

    private void cRadioButtonActionPerformed(ActionEvent evt) {
        String a = aTextField.getText();
        int i = Integer.parseInt(a);
        String b = bTextField.getText();
        int j = Integer.parseInt(b);
        int k = i * j;
        cTextField.setText(Integer.toString(k));
    }

    private void dRadioButtonActionPerformed(ActionEvent evt) {
        String a = aTextField.getText();
        int i = Integer.parseInt(a);
        String b = bTextField.getText();
        int j = Integer.parseInt(b);
        int k = i / j;
        cTextField.setText(Integer.toString(k));
    }

    }


Here is the stack trace I receive:

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "vvvv"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at Main.aRadioButtonActionPerformed(Main.java:154)
at Main.access$0(Main.java:152)
at Main$2.actionPerformed(Main.java:78)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.JToggleButton$ToggleButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

您需要将try-
catch移至操作预先执行的方法，现在，仅当Java设置GUI时它们才在其中，当用户执行操作预先执行的操作（actionPreformed）时，这些方法将被调用，因此它们需要try-
捕获，而不是设置方法。

private void cRadioButtonActionPerformed(ActionEvent evt) {
    try {

          String a = aTextField.getText();
          int i = Integer.parseInt(a);
          String b = bTextField.getText();
          int j = Integer.parseInt(b);
          int k = i * j;
          cTextField.setText(Integer.toString(k));

       } catch (NumberFormatException e) {
          JOptionPane.showMessageDialog(null,
                "Error: You must enter an integer");

       } catch (ArithmeticException e) {
          JOptionPane.showMessageDialog(null,
                "Error: You cannot divide by zero");
    }
}

将try-
catch添加到使用该相似代码的所有ActionPreformed方法中，只需确保每个actionPreformed方法仍具有其自己的代码即可，只需在其周围加上try-
catch块即可