多个按钮的单个动作侦听器

Question

谁能帮助我如何在多个按钮上添加单个动作侦听器？ 这是我的多个按钮的多动作侦听器代码。 我还尝试将一个通用按钮用作所有按钮的动作侦听器。 任何人都可以建议我一个相关的答案。 我是初学者，我对Java没有太多了解。

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

public class Calculator {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        JFrame frame = new JFrame();     //object of JFrame
        JLabel firstValue, secondValue, result, answer;     //declaration of JLabel
        JTextField one, two;     //declaration of JTextField
        JButton addition, subtraction, multiplication, division;     //declaration of JButton

        //Label for first value
        firstValue = new JLabel("First Value:");
        firstValue.setBounds(50,70,100,30);
        frame.add(firstValue);      

        //Label for second value
        secondValue = new JLabel("Second Value:");
        secondValue.setBounds(50,120,100,30);
        frame.add(secondValue);     

        //TextFields for first value    
        one = new JTextField();
        one.setBounds(170, 70, 105, 30);
        frame.add(one);

        //TextFields for second value
        two = new JTextField();
        two.setBounds(170, 120, 105, 30);
        frame.add(two);

        //Button for addition
        addition = new JButton("+");
        addition.setBounds(50, 170, 45, 30);
        frame.add(addition);

        //Button for subtraction
        subtraction = new JButton("-");
        subtraction.setBounds(110, 170, 45, 30);
        frame.add(subtraction);

        //Button for multiplication
        multiplication = new JButton("*");
        multiplication.setBounds(170, 170, 45, 30);
        frame.add(multiplication);

        //Button for division
        division = new JButton("/");
        division.setBounds(230, 170, 45, 30);
        frame.add(division);

        //Label for Result
        result = new JLabel("Result");
        result.setBounds(50, 220, 100, 30);
        frame.add(result);

        //TextFields for first value    
        answer = new JLabel();
        answer.setBounds(170, 220, 105, 30);
        frame.add(answer);

        //actionListener for addition button
        addition.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                //logic for addition
                int finalAnswer = Integer.parseInt(one.getText()) + Integer.parseInt(two.getText());
                answer.setText(Integer.toString(finalAnswer));

            }
        });


        //actionListener for subtraction button
        subtraction.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                //logic for addition
                int finalAnswer = Integer.parseInt(one.getText()) - Integer.parseInt(two.getText());
                answer.setText(Integer.toString(finalAnswer));              
            }
        });

        //actionListener for multiplication button
        multiplication.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                //logic for addition
                int finalAnswer = Integer.parseInt(one.getText()) * Integer.parseInt(two.getText());
                answer.setText(Integer.toString(finalAnswer));              
            }
        });     

        //actionListener for division button
        division.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                //logic for addition
                int finalAnswer = Integer.parseInt(one.getText()) / Integer.parseInt(two.getText());
                answer.setText(Integer.toString(finalAnswer));              
            }
        });     

        frame.setSize(400,400);     //set size of JFrame with width and height
        frame.setLayout(null);      //set layout type by null
        frame.setVisible(true);     //set JFrame visible by boolean value true/false    
    }
}

Answer 1

通常，您会执行以下操作（您可以将其附加到您的 Calculator 类中）：

class Calculator {

  private JButton subtraction;

  public static void main(String[] args) {
    // your code

    // button example
    subtraction = new JButton("-");
    subtraction.addActionListener(new Listener());

    // your code
  }

  class Listener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
      if (e.getSource() == nameOfJButton) {
        // do the action for this button
      } else if (e.getSource() == nameOfAnotherButton) {
        // you get the idea
      }
    }

  }

}

现在，您可以像这样更改代码：

// actionListener for addition button
addition.addActionListener(new Listener());

Answer 2

这是针对您的问题的一些高级解决方案。 主要思想是将您的操作作为您的操作的参数。 此外，我使用类AbstractAction而不是ActionListener来定义按钮。 它允许结合文本和动作。 所以代码看起来更小更智能。

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.util.function.BiFunction;

import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import javax.swing.border.EmptyBorder;

/**
 * <code>ButtonExample</code>.
 */
public class ButtonExample {
    private JTextField one, two;

    private final JLabel answer = new JLabel();

    private class ArithmeticAction extends AbstractAction {
        private final BiFunction<Integer, Integer, Integer> arithmeticFunction;

        public ArithmeticAction(String name, BiFunction<Integer, Integer, Integer> arithmeticFunction) {
            super(name); // set name of button
            this.arithmeticFunction = arithmeticFunction;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            Integer firstOperand = Integer.valueOf(one.getText());
            Integer secondOperand = Integer.valueOf(two.getText());
            Integer result = arithmeticFunction.apply(firstOperand, secondOperand);
            answer.setText(result.toString());
        }
    }

    private void initUI() {
        one = new JTextField(5);
        two = new JTextField(5);
        JPanel panel = new JPanel(new GridLayout(3, 2, 5, 5));
        panel.add(new JLabel("First value:"));
        panel.add(one);
        panel.add(new JLabel("Second value:"));
        panel.add(two);
        panel.add(new JLabel("Result:"));
        panel.add(answer);
        panel.setBorder(new EmptyBorder(0, 5, 0, 5));
        JPanel operations = new JPanel();
        operations.add(new JButton(new ArithmeticAction("+", (a, b) -> a + b)));
        operations.add(new JButton(new ArithmeticAction("-", (a, b) -> a - b)));
        operations.add(new JButton(new ArithmeticAction("*", (a, b) -> a * b)));
        operations.add(new JButton(new ArithmeticAction("/", (a, b) -> a / b)));
        JFrame frm = new JFrame();
        frm.add(panel);
        frm.add(operations, BorderLayout.NORTH);
        frm.pack();
        frm.setLocationRelativeTo(null);
        frm.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        frm.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new ButtonExample()::initUI);
    }
}

小解释：

BiFunction是一个标准接口，它变成两个参数，并返回一个值。 你可以像这样实现它：

BiFunction<Integer, Integer, Integer> sum = (a, b) -> a + b;

这意味着该函数接受两个参数： a和b并返回值a + b 。 这种可能性是在 Java 8 中添加的。