swing Java程序，使用两个滑块生成两个数字相加

Question

我有一个java类的作业，我必须使用滑块添加两个数字，我真的被卡住了。这是我的代码：

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

public class slideCalculator {
JButton add,subtract;
JSlider num1st,num2nd;
JLabel answer;
public slideCalculator(){
    JFrame calc = new JFrame("Mediocre Calculator");
    num1st = new JSlider (0, 100, 0);
    num1st.setMajorTickSpacing (10);
    num1st.setMinorTickSpacing (5);
    num2nd = new JSlider (0, 100, 0);
    num2nd.setMajorTickSpacing (10);
    num2nd.setMinorTickSpacing (5);
    add = new JButton("+");
    subtract = new JButton("-");
    answer = new JLabel("");
    calc.setDefaultCloseOperation(calc.EXIT_ON_CLOSE);
    calc.setVisible(true);
    calc.setBounds(500, 200, 290, 210);
    calc.setLayout(new GridLayout(0,2,1,1));
    calc.add(new JLabel("First Number: "));
    calc.add(num1st);
    calc.add(new JLabel("Second Number: "));
    calc.add(num2nd);
    calc.add(new JLabel("Answer: "));
    calc.add(answer);
    calc.add(add);
    calc.add(subtract);
    add.addActionListener(new action());
    subtract.addActionListener(new action());

}
public static void main(String[] args) {
    slideCalculator lc = new slideCalculator();
}
public class action implements ActionListener {
    public void actionPerformed(ActionEvent ae) {
        int firstNum = Integer.parseInt(num1st.getValue());
        int secondNum = Integer.parseInt(num2nd.getValue());
        if(ae.getValue()== add){
            answer.setText(String.valueOf(firstNum+secondNum));
        }
        else if (ae.getValue()==subtract){
            answer.setText(String.valueOf(firstNum-secondNum));
        }
        } 

}
}

当我去运行它时，它不想工作。我可能错过了一些东西，但我似乎无法理解。我说得对吗

Answer 1

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

public class slideCalculator {
JButton add,subtract;
JSlider num1st,num2nd;
JLabel answer;
public slideCalculator(){
    JFrame calc = new JFrame("Mediocre Calculator");
    num1st = new JSlider (0, 100, 0);
    num1st.setMajorTickSpacing (10);
    num1st.setMinorTickSpacing (5);
    num2nd = new JSlider (0, 100, 0);
    num2nd.setMajorTickSpacing (10);
    num2nd.setMinorTickSpacing (5);
    add = new JButton("+");
    subtract = new JButton("-");
    answer = new JLabel("");
    calc.setDefaultCloseOperation(calc.EXIT_ON_CLOSE);
    calc.setVisible(true);
    calc.setBounds(500, 200, 290, 210);
    calc.setLayout(new GridLayout(0,2,1,1));
    calc.add(new JLabel("First Number: "));
    calc.add(num1st);
    calc.add(new JLabel("Second Number: "));
    calc.add(num2nd);
    calc.add(new JLabel("Answer: "));
    calc.add(answer);
    calc.add(add);
    calc.add(subtract);
    add.addActionListener(new action());
    subtract.addActionListener(new action());

}
public static void main(String[] args) {
    slideCalculator lc = new slideCalculator();
}
public class action implements ActionListener {
    public void actionPerformed(ActionEvent ae) {
        int firstNum = num1st.getValue();
        int secondNum = num2nd.getValue();
        if("+".equals(ae.getActionCommand())) {
            answer.setText(String.valueOf(firstNum+secondNum));
        }
        else 
        if ("-".equals(ae.getActionCommand())) {
            answer.setText(String.valueOf(firstNum-secondNum));
        }
        } 

}
}

Answer 2

这里有两个编译错误源

JSlider#getValue返回一个int值，因此不需要使用Integer.parseInt，它需要一个String。相反，你可以使用：

int firstNum = num1st.getValue();
int secondNum = num2nd.getValue();

另外getValue对于ActionEvent是未定义的，getSource将为JButton提供Object参考：

Object source = ae.getSource();
if (ae.getSource() == add) {
   answer.setText(String.valueOf(firstNum + secondNum));
} else if (source == subtract) {
   answer.setText(String.valueOf(firstNum - secondNum));
}

Answer 3

这是：

public void actionPerformed(ActionEvent ae) {
    int firstNum = Integer.parseInt(num1st.getValue());
    int secondNum = Integer.parseInt(num2nd.getValue());
    if(ae.getValue()== add){  // *****

毫无意义。{cd1}甚至没有编译动作}。您不会获得ActionEvent的“值”，而是通过getActionCommand()获取其actionCommand字符串，然后可以使用String的equals(...)或equalsIgnoreCase(...)方法将其与其他字符串进行比较

也就是说

if ("+".equals(ae.getActionCommand()) {
   // do addition
} else if ("-".equals(ae.getActionCommand()) {
   // do subtraction
}

在以后的问题中，如果您发现任何编译器错误，请发布所有编译器错误