Question

该程序应该转换用户输入的里程并使用GUI界面转换为公里。程序目前无法编译。

aaaaa.java:10：错误：方法声明无效;需要返回类型 public CalcPanel（）{ ^ 1错误

无论我在哪里查找此类程序的示例，我都看不到使用该方法的返回类型。有任何想法吗？感谢

以下是该计划：

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

public class aaaaa extends JFrame {
private JLabel messageLabel= new JLabel("Enter distance in miles");
private JTextField milesTextField = new JTextField(10);;
private JButton calcButton = new JButton("Calculate"); 

public CalcPanel() {
    JPanel panel = new JPanel();
    panel.add(messageLabel);
    panel.add(milesTextField);
    panel.add(calcButton);

    calcButton.addActionListener(new CalcButtonListener());
}

public static void main(String[] args) {
        JFrame frame = new CalcPanel();
        frame.setTitle("M to Km Converter");
        frame.setLocationRelativeTo(null);
        frame.setSize(300, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
}

class CalcButtonListener implements ActionListener {        public void actionPerformed(ActionEvent e) {
        String input = milesTextField.getText();
        double kilometers = Double.parseDouble(input) * 1.6023;
        JOptionPane.showMessageDialog(null, input + " miles is " + kilometers + " kilometers.");
    }
}
}

所以问题解决了，但这是另一个问题。该面板弹出，但我的messageLabel milesTextField calcButton没有显示。

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

    public class Aaaa extends JFrame {
    private JPanel panel;
    private JLabel messageLabel= new JLabel("Enter distance in miles");
    private JTextField milesTextField = new JTextField(10);;
    private JButton calcButton = new JButton("Calculate"); 

    public Aaaa() {
        JPanel panel = new JPanel();
        panel.add(messageLabel);
        panel.add(milesTextField);
        panel.add(calcButton);
        setVisible(true);
        calcButton.addActionListener(new CalcButtonListener());
    }

    public static void main(String[] args) {
            JFrame frame = new Aaaa();
            frame.setTitle("M to Km Converter");
            frame.setLocationRelativeTo(null);
            frame.setSize(300, 150);
    }

    class CalcButtonListener implements ActionListener {        public void actionPerformed(ActionEvent e) {
            String input = milesTextField.getText();
            double kilometers = Double.parseDouble(input) * 1.6023;
            JOptionPane.showMessageDialog(null, input + " miles is " + kilometers + " kilometers.");
        }
    }
}

Answer 1

您正在尝试创建构造函数，但构造函数的名称与类的名称不匹配。

改为public CalcPanel改为public aaaaaa。

Answer 2

似乎是一个拼写错误，类和构造函数名称不匹配。您的类名是aaaaa，而构造函数名称是CalcPanel。

Java GUI错误的麻烦

2 个答案: