Question

我已经使用swing和ActionListener在Java中创建了一个程序，该程序只是将km转换为英里，反之亦然。在actionPerformed上，我试图将值返回到输出变量，但无法在JTextArea中获取该值。下面的代码：

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

public class Converter extends JFrame implements ActionListener {
    JLabel label = new JLabel("Distance : ");
    JTextField input = new JTextField(10);
    JButton button = new JButton("Convert");
    JTextArea output = new JTextArea(10,15);
    CheckboxGroup cbg = new CheckboxGroup();
    Checkbox cb1 = new Checkbox("Convert MILES to KM", cbg, true);
    Checkbox cb2 = new Checkbox("Convert KM to MILES", cbg, false);

    public static void main(String args[]){
        Converter s = new Converter();
        s.setVisible(true);
    }

    public Converter(){
        setLayout(null);
        setSize(300,400);  
        //left-down-width-hegiht
        cb1.setBounds(60,30,150,30);
        cb2.setBounds(60,60,150,30);
        label.setBounds(30,90,120,30);
        input.setBounds(90,95,170,20);
        button.setBounds(100,130,90,30);
        output.setBounds(45,168,200,165);
                
        add(cb1);
        add(cb2);
        add(label);
        add(input);
        add(button);
        add(output);
    }

    public void actionPerformed(ActionEvent e){
        if (cb1 .equals(true) ) {
            if (e.getSource() == button ){
                double d = Double.parseDouble(input.getText());
                double d2 =  d* 0.62;
                String str2 = String.valueOf(d2); 

                output.setText(str2);
            }
            else { 
            }
        }
    }        
}

Answer 1

2件事：

复选框上的复选框错误。应该是：
```
if (cb1.getState()) {...}
```
您必须在按钮中注册动作监听器：在构造函数中添加：
```
button.addActionListener(this);
```

java swing程序转换器km到英里，反之亦然

1 个答案: