Java:Joptionpane 消息对话框未打开

Question

我决定制作一个简洁的小计算器程序，但现在，当我按下计算并运行计算脚本时，它不会打开一个说明答案的框。我找不到问题所在。谁能告诉我一下？

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Gui extends JFrame{

    private JTextField text;
    private JTextField text2;
    private JRadioButton plus;
    private JRadioButton divide;
    private JRadioButton multiply;
    private JRadioButton subtract;
    private ButtonGroup group;
    private JButton button;
    private int str = 1;
    private String txt;
    private String txt2;
    private int num1;
    private int num2;
    private int ans;

    public Gui(){

        super("Calculator");
        setLayout(new FlowLayout());

        text = new JTextField(10);
        text2 = new JTextField(10);
        add(text);
        add(text2);
        plus = new JRadioButton("Add", true);
        divide = new JRadioButton("Divide", false);
        multiply = new JRadioButton("Multiply", false);
        subtract = new JRadioButton("Subtract", false);
        group = new ButtonGroup();
        group.add(plus);
        group.add(divide);
        group.add(multiply);
        group.add(subtract);
        add(plus);
        add(divide);
        add(multiply);
        add(divide);
        add(subtract);
        button = new JButton("Calculate");
        add(button);

        plus.addItemListener(
                new ItemListener(){
                    public void itemStateChanged(ItemEvent event){
                        str = 1;
                        System.out.println(str);
                    }
                }
            );
        divide.addItemListener(
                new ItemListener(){
                    public void itemStateChanged(ItemEvent event){
                        str = 2;
                        System.out.println(str);
                    }
                }
            );
        multiply.addItemListener(
                new ItemListener(){
                    public void itemStateChanged(ItemEvent event){
                        str = 3;
                        System.out.println(str);
                    }
                }
            );
        subtract.addItemListener(
                new ItemListener(){
                    public void itemStateChanged(ItemEvent event){
                        str = 4;
                        System.out.println(str);
                    }
                }
            );
        HandlerClass handler = new HandlerClass();
        button.addActionListener(handler);

    }

    private class HandlerClass implements ActionListener{
        public void ActionPerformed(ActionEvent event){
                txt = text.getText();
                txt2 = text2.getText();
                num1 = Integer.parseInt(txt);
                num2 = Integer.parseInt(txt2);
                if(str==1){
                    ans=num1+num2;
                }
                if(str==2){
                    ans=num1/num2;
                }
                if(str==3){
                    ans=num1*num2;
                }
                if(str==4){
                    ans=num1-num2;
                }
                JOptionPane.showMessageDialog(null, String.format("Answer: %s", ans));

            }
        }
    }

如果需要，这里是运行它的脚本:

import javax.swing.JFrame;

public class apples {
    public static void main(String[] args){
        Gui bucky = new Gui();
        bucky.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        bucky.setSize(300,150);
        bucky.setVisible(true);
    }
}

这是我点击“计算”时的错误代码:

线程“AWT-EventQueue-0”中的异常 java.lang.Error: Unresolved 编译问题: 类型 Gui.HandlerClass 必须实现继承的抽象方法 ActionListener.actionPerformed(ActionEvent)

at Gui$HandlerClass.actionPerformed(Gui.java:85)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.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$000(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

您正在尝试运行不可编译的代码——不要这样做!

而是在编译时修复所有编译问题，然后仅在代码编译良好时运行。

首先:您需要正确地将 actionPerformed(...) 大写。

下一步:您的 JRadioButton 上不应该有 任何 监听器。而是检查仅在主要计算 JButton 的 ActionListener 中按下了哪个按钮。原因是您不关心用户是否选择了一个 JRadioButton 然后又改变了主意并选择了另一个，而是您只关心在按下计算 JButton 时选择了哪个 JRadioButton。