java - 使用 java 中另一个类的方法更新 jbutton 的 jlabel onclick

Question

我有一个名为driver的类，在这个类中我有一个gui，它有一个jbutton和一个jlabel

单击jbutton 我正在用随机数学问题更新jlabel。

当程序启动时，

Jlabel = "Welcome Students"
Jbutton = "Start!"

点击

jlabel = "a math problem here"
Jbutton = "Click For Answer"

下一次点击

jlabel = "Answer for the math problem"
jbutton = "Next question"

此时 jlabel 和 jbutton 将处于循环状态交替

jlabel = alternate math problem and answer
jbutton Click For Answer and Next Question

到目前为止，我不知道如何添加第二个 onclick 函数以及数学问题的时间出现在 jlabel 中的内容是 MathProblems@49bcf06 或始终跟随 MathProblems 的一些随机数字和字母。

这是我的代码，

驱动程序类别

import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.*;

import javax.swing.*;

public class Driver extends MathProblems {

    MathProblems question = new MathProblems();
    MathProblems expected = new MathProblems();

    String s = "Welcome Students!";
    String b = "Start!";
    private JFrame f;
    private JPanel p;

    JFrame frame = new JFrame();

    JButton b1 = new JButton(b);

    JLabel jl = new JLabel(s);

    int i;

    public Driver () {      
        gui();  

    }

    public void gui() { 
        f = new JFrame("Flash Card Program");       
        p = new JPanel();   
        f.setLayout( new GridLayout( 2, 1 ) );
        f.add(jl);
        f.add(p);
        p.setLayout( new GridLayout( 2, 1 ) );
        p.add(b1);

        jl.setHorizontalAlignment(JLabel.CENTER);

        // pack the frame for better cross platform support
        f.pack();
        // Make it visible
        f.setVisible(true);
        f.setSize(560,400); // default size is 0,0
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        b1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e){
                String b = "Click For Answer";
                b1.setText(b.toString());
                jl.setText(question.toString());

          }
      });

        b1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e){
                String b = "Next Question";
                b1.setText(b.toString());
                jl.setText(expected.toString());

          }
      });
    }


    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
           public void run() {
                new Driver();
                new MathProblems();

           }
        });
    } // End main Method

       } // End class Driver

数学问题类

import java.util.Random;
import java.util.Scanner;

public class MathProblems {
     private static final int MAX_NUMBER = 10;
     private static final Scanner in = new Scanner(System.in);
     private static final Random random = new Random();

     public void run() {
         while(true) {  
             final int a = random.nextInt(MAX_NUMBER);
             final int b = random.nextInt(MAX_NUMBER);

             final int type = random.nextInt(4);

             switch (type) {
                case 0: 
                   add(a, b);
                break;
                case 1: 
                   subtract(a, b);
                break;
                case 2:
                   multiply(a, b);
                break;
                case 3:
                    divide(a, b);
                 break;
             }
         }  
     }

     private void add(final int a, final int b) {
         final int expected = a + b;

         final int answer = askQuestion(a + " + " + b + "=");

         checkResult(expected, answer); 
     }

     private void subtract(final int a, final int b) {
         final int expected = a - b;

         final int answer = askQuestion(a + " - " + b + "=");

         checkResult(expected, answer); 
     }

     private void multiply(final int a, final int b) {
         final int expected = a * b;

         final int answer = askQuestion(a + " * " + b + "=");

         checkResult(expected, answer); 
     }

     private void divide(final int a, final int b) {
         final int expected = a / b;

         final int answer = askQuestion(a + " / " + b + "=");

         checkResult(expected, answer); 
     }

     private int askQuestion(final String question) {
         System.out.print(question);

         return in.nextInt(); 
     }  

     private void checkResult(final int expected, final int answer) {
         if (expected == answer) {
            System.out.println("Correct answer! You rock!");
         } else {
            System.out.println("WROOONG! You suck!");
         }    
     } 

}

Answer 1

您获得 MathProblems@49bcf06 作为输出的原因是您在 MathProblems 上调用 toString() 而没有覆盖它。您获得的输出是 MathProblems 对象的哈希码，这是 toString() 的默认行为。在 MathProblems 中，您必须定义以下内容:

@Override
public String toString()
{
   // return the String you want displayed.
}

<小时/>您遇到的另一个问题是，当您将第二个 ActionListener 添加到 b1 时，它会覆盖第一个。我还没有尝试运行您的代码，但我认为这会导致您的按钮始终显示“下一个问题”，并且标签将始终显示来自 expected 的字符串，而不是来自 回答。你可以尝试这样的事情:

b1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e){
            if(b1.getText().equals("Click For Answer")
            {
                String b = "Next Question";
                b1.setText(b);
                jl.setText(expected.toString());
            }
            else
            {
                String b = "Click For Answer";
                b1.setText(b);
                jl.setText(question.toString());
            }
      }
});

此外，您不需要对 b 调用 toString()，因为它已经是一个 String。

<小时/>

编辑:

驱动程序类别:

import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.*;

import javax.swing.*;

public class Driver extends MathProblems {

    MathProblems problems = new MathProblems();
    private static final Scanner in = new Scanner(System.in);

    String s = "Welcome Students!";
    String b = "Start!";
    private JFrame f;
    private JPanel p;

    JFrame frame = new JFrame();

    JButton b1 = new JButton(b);

    JLabel jl = new JLabel(s);

    int i;

    public Driver () {      
        gui();  
    }

    public void gui() { 
        f = new JFrame("Flash Card Program");       
        p = new JPanel();   
        f.setLayout( new GridLayout( 2, 1 ) );
        f.add(jl);
        f.add(p);
        p.setLayout( new GridLayout( 2, 1 ) );
        p.add(b1);

        jl.setHorizontalAlignment(JLabel.CENTER);

        // pack the frame for better cross platform support
        f.pack();
        // Make it visible
        f.setVisible(true);
        f.setSize(560,400); // default size is 0,0
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        b1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e){
                if(b1.getText().equals("Click For Answer")
                {
                    String s = in.nextLine();
                    int answer = Integer.parseInt(s);
                    String result = problems.checkResult(answer);
                    j1.setText(result);
                    String b = "Next Question";
                    b1.setText(b);
                }
                else
                {
                    problems.run();
                    j1.setText(problems.getQuestion());
                    String b = "Click For Answer";
                    b1.setText(b);

                }
          }
});
    }


    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
           public void run() {
                new Driver();
           }
        });
    } // End main Method

} // End class Driver

<小时/>数学问题课:

import java.util.Random;
import java.util.Scanner;

public class MathProblems {
     private static final int MAX_NUMBER = 10;
     private static final Random random = new Random();

     private int expected = 0;
     private String question = "";

     public void run() {
         final int a = random.nextInt(MAX_NUMBER);
         final int b = random.nextInt(MAX_NUMBER);

         final int type = random.nextInt(4);

         switch (type) {
             case 0: 
                 add(a, b);
                 break;
             case 1: 
                subtract(a, b);
                break;
             case 2:
                multiply(a, b);
                break;
             case 3:
                 divide(a, b);
                 break;
         }
     }

     private void add(final int a, final int b) {
         expected = a + b;

         askQuestion(a + " + " + b + "=");
     }

     private void subtract(final int a, final int b) {
         expected = a - b;

         askQuestion(a + " - " + b + "=");
     }

     private void multiply(final int a, final int b) {
         expected = a * b;

         askQuestion(a + " * " + b + "=");
     }

     private void divide(final int a, final int b) {
         expected = a / b;

         askQuestion(a + " / " + b + "=");
     }

     private int askQuestion(final String question) {
         this.question = question;
     }  

     public String getQuestion() {
         return question;
     }

     public String checkResult(final int answer) {
         if (expected == answer) {
            return "Correct answer! You rock!";
         } else {
            return "WROOONG! You suck!";
         }    
     } 

}