Question

我正在尝试制作一个带有按钮的gui程序，当你点击它时，你会从1到6掷出一个模具，然后会出现一个模具图像。但是当我尝试生成1到6之间的数字时，会出现一个无法找到符号的错误。

int rolledNumber = random.nextInt(max - min + 1) + min;

我已经宣布最大和最小为6和1。

我也在尝试获得1到6之间的随机int的部分出错。而我用来打开图像的代码似乎是错误的。

`

img = ImageIO.read(new File("dice 1.jpeg"));

这是我的代码：

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



public class Butttin {  
    public static void main(String[] args) {    
        JFrame frame = new JFrame("Rolling Dice Game");
        JPanel panel = new JPanel();
        JButton buttonRoll = new JButton("Roll!");

        buttonRoll.addActionListener(new buttonRoll()); 

        panel.setLayout(new GridLayout(5, 2, 5, 5));
        frame.setVisible(true);
        frame.setSize(500, 500);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
    }

    private static class buttonRoll implements ActionListener {

        public void actionPerformed(ActionEvent event) {
            int max = 6;
            int min = 1;
            int rolledNumber = random.nextInt(max - min + 1) + min;
            String command  = event.getActionCommand();
            if (command == "Roll!") {
                if (rolledNumber == 1) {
                    JLabel die = new JLabel();
                    img = ImageIO.read(new File("dice 1.jpeg"));
                } else if (rolledNumber == 2){
                    JLabel die = new JLabel();
                    img = ImageIO.read(new File("dice 2.jpg"));
                } else if (rolledNumber == 3){
                    JLabel die = new JLabel();
                    img = ImageIO.read(new File("dice 3.jpg"));
                } else if (rolledNumber == 4){
                    JLabel die = new JLabel();
                    img = ImageIO.read(new File("dice 4.jpg"));
                } else if (rolledNumber == 5){
                    JLabel die = new JLabel();
                    img = ImageIO.read(new File("dice 5.jpg"));
                } else if (rolledNumber == 6){
                    JLabel die = new JLabel();
                }
                return die; 
            }
        }
    }
}

Answer 1

random不是有效的类或变量，我认为你的意思是java.util.Random，你需要去掉变量并创建一个......的实例。

private static class ButtonRoll implements ActionListener {

    private java.util.Random random = new java.util.Random();

接下来，if (command == "Roll!") {不是您在Java中比较String的方式，您应该使用String#equals，例如if ("Roll!".equals(command)) {

接下来，img = ImageIO.read(new File("dice 1.jpeg"));受到影响，部分来自同一问题。 img未定义。此外，ImageIO.read会抛出您未处理的IOException。有关详细信息，请参阅JavaDocs

接下来，您要在die语句的本地上下文中声明if

            if (rolledNumber == 1) {
                JLabel die = new JLabel();
                img = ImageIO.read(new File("dice 1.jpeg"));
            } else if (rolledNumber == 2) {
                JLabel die = new JLabel();

这意味着当您尝试使用return die , die`时，未定义。确保在上下文级别声明要在...

中使用它

        int rolledNumber = random.nextInt(max - min + 1) + min;
        String command = event.getActionCommand();
        JLabel die = null;
        if ("Roll!".equals(command)) {
            if (rolledNumber == 1) {
                die = new JLabel();
                img = ImageIO.read(new File("dice 1.jpeg"));
            } else if (rolledNumber == 2) {

请注意，我不认为你想创建一个JLabel，而是改变一个已有的标签icon属性......

最后，ActionListener#actionPerformed没有定义返回类型（它被定义为void），这意味着return die;是非法声明......

您必须找出允许buttonRoll类更新UI的方法

另外，为什么我要解析您的代码，您确实应该确保只在事件调度线程的上下文中创建和修改您的UI，请参阅Initial Threads更多细节

因为我知道它会来......

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Butttin {

    public static void main(String[] args) {
        new Butttin();
    }

    public Butttin() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel output;
        private JButton roll;

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;

            output = new JLabel("-");
            add(output, gbc);

            roll = new JButton("Roll");
            add(roll, gbc);

            roll.addActionListener(new RollActionListener(output));

        }

    }

    public class RollActionListener implements ActionListener {

        private JLabel label;
        private Random random = new Random();

        public RollActionListener(JLabel label) {
            this.label = label;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            int max = 6;
            int min = 1;
            int rolledNumber = random.nextInt(max - min + 1) + min;

            label.setText(Integer.toString(rolledNumber));
        }
    }

}

GUI编程和上传图像？

1 个答案: