如何使某些按钮执行不同的操作？ Java Swing JButton

Question

我正在制作一个可以计算GPA并返回当前类所需的GPA的GUI，以获得目标GPA。 我让用户输入他们所采用的所有先前/当前/将来的类，并且我有几个按钮可以将这些信息输入到单独的变量中，稍后我将进行计算。 但是，我的按钮都没有执行任何操作。 有人可以向我解释我的代码有什么问题吗？ 我尝试了两种不同的方法（均在示例中进行了介绍），但两种方法均无效。

import java.awt.BorderLayout;
import java.awt.ComponentOrientation;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.lang.reflect.Array;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class GUI extends JFrame implements ActionListener {

    private FlowLayout flowlayout = new FlowLayout();
    private GridLayout gridlayout = new GridLayout(6, 6);
    private JLabel instructions;
    private JLabel enteredclasses;
    private JLabel status1, status2, status3, status4, status5, status6;
    private JTextField classinput1, classinput2, classinput3, classinput4, classinput5, classinput6;
    private JTextField hoursinput1, hoursinput2, hoursinput3, hoursinput4, hoursinput5, hoursinput6;
    private JComboBox<String> gradeinput1, gradeinput2, gradeinput3, gradeinput4, gradeinput5, gradeinput6;
    private JPanel panel2 = new JPanel();
    private JButton add1, add2, add3, add4, add5, add6;
    private JButton remove1, remove2, remove3, remove4, remove5, remove6;
    private String[] grades = {"Select Grade (optional)", "A", "A-", "B+", "B", "B-", "C+", "C", "C-", "D+", "D", "D-", "F"};
    private double gpa1, gpa2, gpa3, gpa4, gpa5, gpa6;
    private ArrayList<Array> matrix;
    private String[] row1 = new String[3];
    private String[] row2 = new String[3];
    private String[] row3 = new String[3];
    private String[] row4 = new String[3];
    private String[] row5 = new String[3];
    private String[] row6 = new String[3];

    public GUI(String name) {
        super(name);
    }

    public void addComponentsToPanel(Container pane) {
        JPanel panel1 = new JPanel();
        panel1.setLayout(flowlayout);
        flowlayout.setAlignment(FlowLayout.LEADING);

        instructions = new JLabel("Input the correct information below.");
        panel1.add(instructions);

        panel2.setLayout(gridlayout);

        //creates row 1
        addUserInput(classinput1, hoursinput1);
        addGrades(gradeinput1);
        addButton(add1, "first");
        removeButton(remove1, "second");
        addStatus(status1);

        //creates row 2
        addUserInput(classinput2, hoursinput2);
        addGrades(gradeinput2);
        addButton(add2, "third");
        removeButton(remove2, "fourth");
        addStatus(status2);

        //creates row 3
        addUserInput(classinput3, hoursinput3);
        addGrades(gradeinput3);
        addButton(add3, "fifth");
        removeButton(remove3, "sixth");
        addStatus(status3);

.........

    private static void createAndShowGUI() {
        GUI frame = new GUI("GPA Calculator and Planner Design");
        frame.setSize(300, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.addComponentsToPanel(frame.getContentPane());
        frame.pack();
        frame.setVisible(true);
    }

    public void addUserInput(JTextField name, JTextField credithours) {
        name = new JTextField("Course Name (optional)");
        credithours = new JTextField("Credit Hours");

        panel2.add(name);
        panel2.add(credithours);
    }

    public void addGrades(JComboBox<String> choices) {
        choices = new JComboBox<String>(grades);
        panel2.add(choices);
    }

    public double convertGrade(String grade) {
        String[] grades = {"Select Grade (optional)", "A", "A-", "B+", "B", "B-", "C+", "C", "C-", "D+", "D", "D-", "F"};

        int index = 0;
        for (int i = 0; i < 13; i++) {
            if (grade.equals(grades[i])) {
                index = i;
            }
        }
        double[] gradeconversions = {0.0 , 4.0, 3.67, 3.3, 3.0, 2.67, 2.33, 2.0, 1.67, 1.33, 1.0, .67, 0.0};
        return gradeconversions[index];
    }

    public void addButton(JButton b, String s) {
        b = new JButton("ADD");
        b.setActionCommand(s);
        b.addActionListener(this);
        panel2.add(b);
    }

    public void removeButton(JButton b, String s) {
        b = new JButton("REMOVE");
        b.setActionCommand(s);
        b.addActionListener(this);
        panel2.add(b);
    }

    public void addStatus(JLabel status) {
        status = new JLabel("Status: -");
        panel2.add(status);
    }

    public void addClasses() {

    }

    public static void main(String[] args) {
         javax.swing.SwingUtilities.invokeLater(new Runnable() {
                public void run() {     
                   createAndShowGUI();
                }
            });
    }



    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub

        if (e.getSource() == add1) {
            row1[0] = classinput1.getText();
            row1[1] = hoursinput1.getText();
            row1[2] = (String) gradeinput1.getSelectedItem();
            status1.setText("Status: Added");
        }

        if (e.getActionCommand().equals("third")) {
            row2[0] = classinput1.getText();
            row2[1] = hoursinput1.getText();
            row2[2] = (String) gradeinput1.getSelectedItem();
            status2.setText("Status: Added");
        }

.....

Answer 1

您的actionPerformed方法if (e.getSource() == add1)永远不会为true因为JButton add1始终为null ，因为addButton()方法从未初始化变量add1

因此，您必须声明JButton add1 = new JButton(); 作为类变量，并如下更改addButton方法

public void addButton(JButton b, String s) {
    b.setText("ADD");
    b.setActionCommand(s);
    b.addActionListener(this);
    panel2.add(b);
}

也对removeButton方法应用相同的更改