java - 英里到公里转换器(事件驱动)

Question

我需要创建一个显示Miles 和Kilometers 的JPanel。当您将数字输入其中一个时，它会使用 Enter 键将其转换为另一个。

我不知道如何正确获取 KeyListener 来执行转换。我不是在寻找答案，只是在寻找一些指导或指向类似示例的链接。谢谢。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.*;

import javax.swing.*;

public class Ch09Asg extends JFrame {
    private JTextField jtfMiles = new JTextField(10);
    private JTextField jtfKilo = new JTextField(10);

    public Ch09Asg() {
        JPanel p1 = new JPanel(new GridLayout(2,2));        
        p1.setSize(400,250);
        p1.add(new JLabel("Mile"));
        p1.add(jtfMiles);
        p1.add(new JLabel("Kilometers"));
        p1.add(jtfKilo);
        jtfMiles.setHorizontalAlignment(JTextField.RIGHT);
        jtfKilo.setHorizontalAlignment(JTextField.RIGHT);

        add(p1, BorderLayout.CENTER);

        jtfMiles.addActionListener(new ButtonListener(){
        });

        jtfKilo.addActionListener(new ButtonListener(){
        });
    }

    class ButtonListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            //double mi = convertKmtoMi 
            //Double.parseDouble(jtfMiles.getText());
            //double kilom =
            //Double.parseDouble(jtfKilo.getText());
            //---------------------------------------KILOTOMILE

            String kmStr = jtfKilo.getText();      //Note 3
            double km = Double.parseDouble(kmStr);

            //... Convert it
            double mi = convertKmToMi(km);                //Note 4

            //... Convert it to a string and set mi textfield
            jtfMiles.setText("" + mi); 

            //--------------------------------------MILESTOKILO
            String miStr = jtfMiles.getText();      //Note 3
            double mi2 = Double.parseDouble(miStr);

            //... Convert it
            double km2 = convertKmToMi(mi2);                //Note 4

            //... Convert it to a string and set mi textfield
            jtfMiles.setText("" + km2); 
        }
    }

    public static double convertKmToMi(double kilometers) {
        // Assume there are 0.621 miles in a kilometer.
        double miles = kilometers * 0.621;
        return miles;
    }

    public static double convertMitoKm(double miles) {
        // Assume there are 0.621 miles in a kilometer.
        double kilometers = miles / 0.621;
        return kilometers;
    }

    public static void main(String[] args) {
        Ch09Asg frame = new Ch09Asg();
        frame.pack();
        frame.setTitle("Mile/Kilometer Converter");
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer 1

您应该添加 ActionListener，而不是将 KeyListeners 添加到文本字段，这实际上并不能很好地工作一个按钮的 Action 监听器。当您按下回车键时，它们会被激活。