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

Question

我有一个叫做driver的类，在我的gui中有一个jbutton和一个jlabel

jbutton的jlabel我正在用随机数学问题更新jlabel 。

程序启动时

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

点击

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

下次点击

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

此时，jlabel和jbutton会交替循环

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

到目前为止，我还不知道如何添加第二个onclick函数，并且当jlabel中出现数学问题时，出现的是MathProblems @ 49bcf06或MathProblems后面总是有一些随机数字和字母。

这是我的代码，

驾驶员等级

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

MathProblems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

之所以将MathProblems@49bcf06作为输出，是因为要在MathProblems上调用toString()而不会覆盖它。 您得到的输出是MathProblems对象的哈希 MathProblems ，这是toString()的默认行为。 在MathProblems内部，您将必须定义以下内容：

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

---

您遇到的另一个问题是，将第二个ActionListener添加到b1 ，它将覆盖第一个。 我没有尝试运行您的代码，但是我认为这将导致您的按钮始终显示“下一个问题”，并且标签将始终显示expected的字符串，而永远不会显示来自answer的字符串。 您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()); } } }); 

另外，您不需要在b上调用toString() ，因为它已经是String 。

---

编辑：

驱动类别：

 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 

---

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!"; } } }