在每次单击时创建包含 JTextField、JComboBox 和 JButton 的新行

Question

我正在使用 Java GUI 创建一个 GPA 计算器。当点击“添加课程”按钮时，程序应该每次都为课程名称、学分和成绩添加一个文本字段。

我使用 HTML 和 Javascript 制作了同样的程序，这里是 https://nsuer.club/cgpa-calculator/

看截图：

我应该使用List 来存储文本字段吗？这是我在 Java GUI 上的第一个项目。

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                CgpaCalculator window = new CgpaCalculator();
                window.frmCgpaCalculator.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the application.
 */
public CgpaCalculator() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frmCgpaCalculator = new JFrame();
    frmCgpaCalculator.getContentPane().setFont(new Font("Tahoma", Font.PLAIN, 17));
    frmCgpaCalculator.setTitle("CGPA Calculator");
    frmCgpaCalculator.setBounds(100, 100, 540, 683);
    frmCgpaCalculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frmCgpaCalculator.getContentPane().setLayout(null);

    textField = new JTextField();
    textField.setBounds(12, 140, 126, 29);
    frmCgpaCalculator.getContentPane().add(textField);
    textField.setColumns(10);

    textField_1 = new JTextField();
    textField_1.setBounds(12, 175, 126, 29);
    frmCgpaCalculator.getContentPane().add(textField_1);
    textField_1.setColumns(10);

    textField_2 = new JTextField();
    textField_2.setBounds(12, 210, 126, 29);
    frmCgpaCalculator.getContentPane().add(textField_2);
    textField_2.setColumns(10);

    textField_3 = new JTextField();
    textField_3.setBounds(12, 245, 126, 29);
    frmCgpaCalculator.getContentPane().add(textField_3);
    textField_3.setColumns(10);

    JLabel lblGrade = new JLabel("Course");
    lblGrade.setFont(new Font("Tahoma", Font.PLAIN, 15));
    lblGrade.setBounds(47, 99, 56, 16);
    frmCgpaCalculator.getContentPane().add(lblGrade);

    JComboBox comboBox = new JComboBox();
    comboBox.setToolTipText("0");
    comboBox.setModel(new DefaultComboBoxModel(new String[] {"3", "1", "2", "0", "1.5"}));
    comboBox.setBounds(181, 140, 75, 29);
    frmCgpaCalculator.getContentPane().add(comboBox);

    JLabel lblCredits = new JLabel("Credits");
    lblCredits.setFont(new Font("Tahoma", Font.PLAIN, 15));
    lblCredits.setBounds(192, 99, 56, 16);
    frmCgpaCalculator.getContentPane().add(lblCredits);

    JComboBox comboBox_4 = new JComboBox();
    comboBox_4.setModel(new DefaultComboBoxModel(new String[] {"A", "A-", "B+", "B", "B", "B-", "C+", "C", "D+", "D", "F"}));
    comboBox_4.setBounds(297, 140, 70, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_4);

    JComboBox comboBox_5 = new JComboBox();
    comboBox_5.setModel(new DefaultComboBoxModel(new String[] {"A", "A-", "B+", "B", "B", "B-", "C+", "C", "D+", "D", "F"}));
    comboBox_5.setBounds(297, 175, 70, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_5);

    JComboBox comboBox_6 = new JComboBox();
    comboBox_6.setModel(new DefaultComboBoxModel(new String[] {"A", "A-", "B+", "B", "B", "B-", "C+", "C", "D+", "D", "F"}));
    comboBox_6.setBounds(297, 210, 70, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_6);

    JComboBox comboBox_7 = new JComboBox();
    comboBox_7.setModel(new DefaultComboBoxModel(new String[] {"A", "A-", "B+", "B", "B", "B-", "C+", "C", "D+", "D", "F"}));
    comboBox_7.setBounds(297, 245, 70, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_7);

    JComboBox comboBox_1 = new JComboBox();
    comboBox_1.setModel(new DefaultComboBoxModel(new String[] {"3", "1", "2", "0", "1.5"}));
    comboBox_1.setToolTipText("0");
    comboBox_1.setBounds(181, 175, 75, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_1);

    JComboBox comboBox_2 = new JComboBox();
    comboBox_2.setModel(new DefaultComboBoxModel(new String[] {"3", "1", "2", "0", "1.5"}));
    comboBox_2.setToolTipText("0");
    comboBox_2.setBounds(181, 210, 75, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_2);

    JComboBox comboBox_3 = new JComboBox();
    comboBox_3.setModel(new DefaultComboBoxModel(new String[] {"3", "1", "2", "0", "1.5"}));
    comboBox_3.setToolTipText("0");
    comboBox_3.setBounds(181, 245, 75, 29);
    frmCgpaCalculator.getContentPane().add(comboBox_3);

    JLabel lblGrade_1 = new JLabel("Grade");
    lblGrade_1.setFont(new Font("Tahoma", Font.PLAIN, 15));
    lblGrade_1.setBounds(311, 99, 56, 16);
    frmCgpaCalculator.getContentPane().add(lblGrade_1);

    JButton btnNewButton = new JButton("Add Course");
    btnNewButton.setFont(new Font("Tahoma", Font.PLAIN, 15));
    btnNewButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            JOptionPane.showMessageDialog(frmCgpaCalculator.getComponent(0), "Hello World");
        }
    });

    JLabel lblCgpa = new JLabel("CGPA:");
    lblCgpa.setFont(new Font("Tahoma", Font.BOLD, 17));
    lblCgpa.setBounds(386, 13, 56, 16);
    frmCgpaCalculator.getContentPane().add(lblCgpa);

    JLabel label = new JLabel("0.0");
    label.setFont(new Font("Tahoma", Font.PLAIN, 17));
    label.setBounds(454, 13, 56, 16);
    frmCgpaCalculator.getContentPane().add(label);

    btnNewButton.setBounds(12, 299, 124, 25);
    frmCgpaCalculator.getContentPane().add(btnNewButton);

    JButton btnCalculate = new JButton("Calculate");
    btnCalculate.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            label.setText("3.2");
        }
    });
    btnCalculate.setFont(new Font("Tahoma", Font.PLAIN, 15));
    btnCalculate.setBounds(270, 300, 97, 25);
    frmCgpaCalculator.getContentPane().add(btnCalculate);
}

更新：

如果不需要，我添加了一个按钮来删除一行。如何连接到数组列表索引？

JButton btnX = new JButton("");
    btnX.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

        }
    });
    btnX.setIcon(new ImageIcon(CgpaCalculator.class.getResource("/com/sun/javafx/scene/control/skin/modena/dialog-error.png")));
    btnX.setBackground(Color.RED);
    btnX.setForeground(Color.WHITE);
    btnX.setBounds(428, rowY, 30, 30);
    frmCgpaCalculator.getContentPane().add(btnX);

Answer 1

我将创建一个对象来保存每一行的 3 个元素，称为 CourseRow。并将这些CourseRow 对象存储在List 中。

下面是这样重写的代码：

public class Test {

    public static void main(String[] args) {
        CgpaCalculator window = new CgpaCalculator();
        window.getFrmCgpaCalculator().setVisible(true);
    }
}

class CgpaCalculator {
    private JFrame frmCgpaCalculator;

    private JPanel coursesPanel;
    private JScrollPane scrollPane;

    // Define some constants
    private int ROWS_Y_OFFEST = 0;
    private int ROW_HEIGHT = 35;
    private String[] credits = new String[] {"3", "1", "2", "0", "1.5"};
    private String[] grades = new String[] {"A", "A-", "B+", "B", "B", "B-", "C+", "C", "D+", "D", "F"};

    // This list holds all the row elements
    private List<CourseRow> courseRows = new ArrayList<>();

    // These 2 need to be class variable because we update them in the refresh method
    private JButton btnNewButton, btnCalculate;

    public CgpaCalculator() {
        initializeElements();
        refresh();
    }

    private void initializeElements() {
        frmCgpaCalculator = new JFrame();
        frmCgpaCalculator.getContentPane().setFont(new Font("Tahoma", Font.PLAIN, 17));
        frmCgpaCalculator.setTitle("CGPA Calculator");
        frmCgpaCalculator.setBounds(100, 100, 540, 683);
        frmCgpaCalculator.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frmCgpaCalculator.getContentPane().setLayout(null);

        // CGPA RESULT
        JLabel lblCgpa = new JLabel("CGPA:");
        lblCgpa.setFont(new Font("Tahoma", Font.BOLD, 17));
        lblCgpa.setBounds(386, 13, 56, 16);
        frmCgpaCalculator.getContentPane().add(lblCgpa);

        JLabel label = new JLabel("0.0");
        label.setFont(new Font("Tahoma", Font.PLAIN, 17));
        label.setBounds(454, 13, 56, 16);
        frmCgpaCalculator.getContentPane().add(label);

        // HEADERS
        JLabel lblCourse = new JLabel("Course");
        lblCourse.setFont(new Font("Tahoma", Font.PLAIN, 15));
        lblCourse.setBounds(47, 99, 56, 16);
        frmCgpaCalculator.getContentPane().add(lblCourse);

        JLabel lblCredits = new JLabel("Credits");
        lblCredits.setFont(new Font("Tahoma", Font.PLAIN, 15));
        lblCredits.setBounds(192, 99, 56, 16);
        frmCgpaCalculator.getContentPane().add(lblCredits);

        JLabel lblGrade = new JLabel("Grade");
        lblGrade.setFont(new Font("Tahoma", Font.PLAIN, 15));
        lblGrade.setBounds(311, 99, 56, 16);
        frmCgpaCalculator.getContentPane().add(lblGrade);


        // Courses panel and scroll pane
        coursesPanel = new JPanel();
        coursesPanel.setLayout(null);

        scrollPane = new JScrollPane(coursesPanel);
        scrollPane.setBounds(40, 150, 480, 300);
        scrollPane.setPreferredSize(new Dimension(500, 300));
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        frmCgpaCalculator.getContentPane().add(scrollPane);

        // BUTTONS
        btnNewButton = new JButton("Add Course");
        btnNewButton.setFont(new Font("Tahoma", Font.PLAIN, 15));
        btnNewButton.setBounds(12, 500, 124, 25);
        btnNewButton.addActionListener(new ActionListener() {
               @Override
               public void actionPerformed(ActionEvent arg0) {
                   addCourseRow();
               }
           }
        );
        frmCgpaCalculator.getContentPane().add(btnNewButton);

        btnCalculate = new JButton("Calculate");
        btnCalculate.setFont(new Font("Tahoma", Font.PLAIN, 15));
        btnCalculate.setBounds(270, 500, 97, 25);
        btnCalculate.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                label.setText("3.2");
            }
        });
        frmCgpaCalculator.getContentPane().add(btnCalculate);


        // Add 3 default rows
        addCourseRow();
        addCourseRow();
        addCourseRow();
    }

    // This method refreshes the view.
    // It takes the list of course rows and reposition them depending on their index in the list
    // This enabled to easily handle deleting rows in the middle
    private void refresh() {

        // Reposition all course rows
        int rowY = ROWS_Y_OFFEST;
        CourseRow courseRow;
        for(int rowIndex=0; rowIndex<courseRows.size(); rowIndex++) {
            courseRow = courseRows.get(rowIndex);
            rowY = ROWS_Y_OFFEST + rowIndex * ROW_HEIGHT;

            courseRow.getNameJTextField().setBounds(12, rowY, 126, 29);
            courseRow.getCreditsJComboBox().setBounds(181, rowY, 75, 29);
            courseRow.getGradeJComboBox().setBounds(297, rowY, 70, 29);
            courseRow.getDeleteJButton().setBounds(428, rowY, 30, 30);
        }

        // resize the course panel so the scroll pane knows if it needs to add the scroll bar
        // you need to use the setPreferredSize method
        coursesPanel.setPreferredSize(new Dimension(450, rowY + ROW_HEIGHT));

        // repaint the scroll pane
        scrollPane.invalidate();
        scrollPane.validate();
        scrollPane.repaint();
    }

    private void addCourseRow() {
        // Calculate the Y coordinate of the row
        long rowId = System.currentTimeMillis();

        // Create the 3 elements
        JTextField nameJTextField = new JTextField();
        nameJTextField.setColumns(10);
        coursesPanel.add(nameJTextField);

        JComboBox creditsJComboBox = new JComboBox();
        creditsJComboBox.setToolTipText("0");
        creditsJComboBox.setModel(new DefaultComboBoxModel(credits));
        coursesPanel.add(creditsJComboBox);

        JComboBox gradeJComboBox = new JComboBox();
        gradeJComboBox.setModel(new DefaultComboBoxModel(grades));
        coursesPanel.add(gradeJComboBox);

        JButton btnX = new JButton("");
        btnX.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                removeCourse(rowId);
            }
        });
        btnX.setIcon(new ImageIcon(CgpaCalculator.class.getResource("/com/sun/javafx/scene/control/skin/modena/dialog-error.png")));
        btnX.setBackground(Color.RED);
        btnX.setForeground(Color.WHITE);
        coursesPanel.add(btnX);

        // Add the row to the list
        CourseRow courseRow = new CourseRow();
        courseRow.setId(rowId);
        courseRow.setNameJTextField(nameJTextField);
        courseRow.setCreditsJComboBox(creditsJComboBox);
        courseRow.setGradeJComboBox(gradeJComboBox);
        courseRow.setDeleteJButton(btnX);
        courseRows.add(courseRow);

        refresh();
    }

    private void removeCourse(long rowId) {
        // find the course row by id
        Optional<CourseRow> rowOption = courseRows.stream().filter(r -> r.getId() == rowId).findFirst();
        if(rowOption.isPresent()) {
            CourseRow row = rowOption.get();
            // remove elements of this row from the JFrame
            coursesPanel.remove(row.getNameJTextField());
            coursesPanel.remove(row.getCreditsJComboBox());
            coursesPanel.remove(row.getGradeJComboBox());
            coursesPanel.remove(row.getDeleteJButton());

            // remove row from the list
            courseRows.remove(row);
        } else {
            System.out.println("Could not find row with id "+rowId);
        }

        refresh();
    }



    public JFrame getFrmCgpaCalculator() {
        return frmCgpaCalculator;
    }
}

class CourseRow {
    private long id;
    private JTextField nameJTextField;
    private JComboBox creditsJComboBox;
    private JComboBox gradeJComboBox;
    private JButton deleteJButton;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public JTextField getNameJTextField() {
        return nameJTextField;
    }

    public void setNameJTextField(JTextField nameJTextField) {
        this.nameJTextField = nameJTextField;
    }

    public JComboBox getCreditsJComboBox() {
        return creditsJComboBox;
    }

    public void setCreditsJComboBox(JComboBox creditsJComboBox) {
        this.creditsJComboBox = creditsJComboBox;
    }

    public JComboBox getGradeJComboBox() {
        return gradeJComboBox;
    }

    public void setGradeJComboBox(JComboBox gradeJComboBox) {
        this.gradeJComboBox = gradeJComboBox;
    }

    public JButton getDeleteJButton() {
        return deleteJButton;
    }

    public void setDeleteJButton(JButton deleteJButton) {
        this.deleteJButton = deleteJButton;
    }
}