Java 小程序似乎双重提示

Question

在运行我制作的 Java 小程序（一个基本的猜数小游戏）时，每当它提出问题时，无论是/否或其他问题，它都会询问前几个问题，并执行标准程序以获得结果，然后打开下一个问题并重新打开上一组问题。这会持续很长一段时间，直到您关闭 html 文件才停止。我希望能够看看我的游戏是否真的有效，并可能玩它，虽然它很简单。谁能帮忙解决这个问题？

完整的代码，但前几个问题是问题的真正根源。

import java.applet.Applet;
import java.awt.Graphics;
import javax.swing.JOptionPane;
import java.util.Random;

public class HelloWorld extends Applet {

    public void paint(Graphics g) {

        g.drawString ("James mylastname", 50, 25);
        String ans1 = JOptionPane.showInputDialog("Please input a value");
        String ans2 = JOptionPane.showInputDialog("Please input another value");
        String ans3 = JOptionPane.showInputDialog("Please input a final value");
        double ans1double = Double.parseDouble(ans1);
        double ans2double = Double.parseDouble(ans2);
        double ans3double = Double.parseDouble(ans3);
        double total = ans1double+ans2double+ans3double;
        double average = total/3;
        String answer = Double.toString (average);
        g.drawString ("The average of these three numbers is " + answer, 50, 50);

        Random generator = new Random();
        int x = generator.nextInt(100);
        x++;
        int i;
        // attribute names should be firstWordLowerCase
        int Prime = 5;
        for (i=2; i < x ;i++ ) {
            int n = x%i;
            if (n==0) {
                Prime = 1;
            } else {
                Prime = 0;
            }
        }

        g.drawString ("A random number has been generated, from 0 to 100. " +
            "Follow the dialogue boxes to guess the number. You have three " +
            "chances, and three hints.", 50, 75);
        int even;
        even = JOptionPane.showConfirmDialog(this, "Do you think the number is even?");
        if (even == 0) {
            if (x%2 == 0) {
                g.drawString ("Yes, this number is even.", 50,75);
            }
            if (x%2 != 0) {
                g.drawString ("No, this number is not even.", 50,75);
            }
        }

        if (even == 1) {
            if (x%2 == 0) {
                g.drawString ("Incorrect. This number is even.", 50,75);
            }
            if (x%2 != 0) {
                g.drawString ("Correct. This number is not even.", 50,75);
            }
        }

        // very bad idea to name one attribute 'Prime' and another 'prime'
        int prime;
        prime = JOptionPane.showConfirmDialog(this, "Do you think the number is prime?");
        if (prime == 0) {
            if (Prime == 1) {
                g.drawString ("Sorry, the number is not prime.", 50, 100);
            }
            if (Prime == 0) {
                g.drawString ("Correct, the number is prime.", 50, 100);
            }
        }

        if (prime == 1) {
            if (Prime == 1) {
                g.drawString ("Correct, the number is prime.", 50, 100);
            }
            if (Prime == 0) {
                g.drawString ("Sorry, the number is not prime.", 50, 100);
            }
        }

        int moreless;
        moreless = JOptionPane.showConfirmDialog(this, "Do you think the number is 50 or lower?");
        if (moreless == 0) {
            if (x <= 50) {
                g.drawString ("Correct. The number is 50 or less.", 50, 125);
            }
            if (x > 50) {
                g.drawString ("Incorrect. The number is higher than 50.", 50, 125);
            }
        }

        if (moreless == 1) {
            if (x<= 50) {
                g.drawString ("Incorrect. The number is lower than 50.", 50, 125);
            }
            if (x > 50) {
                g.drawString ("Correct. The number is higher than 50.", 50, 125);
            }
        }

        String guess1 = JOptionPane.showInputDialog("Please guess what you think the number is.");
        double guess1double = Double.parseDouble(guess1);
        if (guess1double == x) {
            g.drawString ("Correct! You guessed the number!", 50, 150);
            return;
        }
        if (guess1double != x) {
            g.drawString ("Incorrect! Please guess again, you have two more tries!", 50, 150);
        }

        String guess2 = JOptionPane.showInputDialog("Please guess again.");
        double guess2double = Double.parseDouble(guess2);
        if (guess2double == x) {
            g.drawString ("Correct! You guessed the number!", 50, 175);
            return;
        }

        if (guess2double != x) {
            g.drawString ("Incorrect! Please guess again, you have one more try!", 50, 150);
        }

        String guess3 = JOptionPane.showInputDialog("Please guess again.");
        double guess3double = Double.parseDouble(guess3);
        if (guess3double == x) {
            g.drawString ("Correct! You guessed the number!", 50, 200);
            return;
        }

        if (guess3double != x) {
            g.drawString ("Incorrect! Sorry, that was your last guess!", 50, 200);
        }
    }
}

Answer 1

将那些只需要执行一次的代码部分放在正确的位置是在init() 方法中。

DemoApplet.java

// <applet code='DemoApplet' width='400' height='400'></applet>
import java.applet.Applet;

public class DemoApplet extends Applet {

    @Override
    public void init() {
        System.out.println("init() once only at start-up");
    }

    @Override
    public void start() {
        System.out.println("start() potentially many times " +
            "(e.g. each time restored from minimized)");
    }

    @Override
    public void stop() {
        System.out.println("stop() potentially many times " +
            "(e.g. each time minimized)");
    }

    @Override
    public void destroy() {
        System.out.println("destroy() once only at shut down");
    }
}

示例 I/O

prompt>appletviewer DemoApplet.java
init() once only at start-up
start() potentially many times (e.g. each time restored from minimized)
stop() potentially many times (e.g. each time minimized)
start() potentially many times (e.g. each time restored from minimized)
stop() potentially many times (e.g. each time minimized)
start() potentially many times (e.g. each time restored from minimized)
stop() potentially many times (e.g. each time minimized)
destroy() once only at shut down

Answer 2

paint 方法中有 UI 创建代码，该方法每秒调用多次以呈现小程序视图。这就是原因。您需要将该代码移至调用一次的init 方法。

http://www.java2s.com/Code/Java/Swing-JFC/DemonstrationofAppletMethods.htm

http://www.cafeaulait.org/course/week5/28.html

Answer 3

问题是您有代码在您的paint() 方法中提示用户。 AWT 会根据需要多次调用该方法来绘制小程序的内容。相反，将此代码移动到您知道只会被调用一次的单独方法中。一个好的候选人是Applet.start()。