Jtable 列中的 ArrayList

Question

我正在创建一个 Jtable，只有一列（月列）并在按钮的帮助下在列中添加一个数组列表。

Arraylist 包含月份的名称，具体取决于选中的月份。

我的问题是当我添加数组列表时，前一行也发生了变化。

我不知道发生了什么。

这是我解决问题的代码

package test;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;

public class Jtable extends JFrame {

    JTable table;
    JButton button;
    JPanel mp;

    DefaultTableModel model;

    JCheckBox chkJan;
    JCheckBox chkFeb;
    JCheckBox chkMarch;
    JCheckBox chkApril;
    JCheckBox chkMay;
    JCheckBox chkJun;
    JCheckBox chkJuly;
    JCheckBox chkAug;
    JCheckBox chkSep;
    JCheckBox chkOct;
    JCheckBox chkNov;
    JCheckBox chkDec;

    List<String> Months = null;

    public Jtable() {

        table = new JTable();
        button = new JButton("Add to Table");
        mp = new JPanel();
        Months = new ArrayList<>();

        chkJan = new JCheckBox("JAN");
        chkFeb = new JCheckBox("FEB");
        chkMarch = new JCheckBox("MARCH");
        chkApril = new JCheckBox("APRIL");
        chkMay = new JCheckBox("MAY");
        chkJun = new JCheckBox("JUN");
        chkJuly = new JCheckBox("JULY");
        chkAug = new JCheckBox("AUG");
        chkSep = new JCheckBox("SEP");
        chkOct = new JCheckBox("OCT");
        chkNov = new JCheckBox("NOV");
        chkDec = new JCheckBox("DEC");

        mp.setLayout(new FlowLayout(FlowLayout.LEFT));
        mp.setSize(300, 200);

        mp.add(chkJan);
        mp.add(chkFeb);
        mp.add(chkMarch);
        mp.add(chkApril);
        mp.add(chkMay);
        mp.add(chkJun);
        mp.add(chkJuly);
        mp.add(chkAug);
        mp.add(chkSep);
        mp.add(chkOct);
        mp.add(chkNov);
        mp.add(chkDec);

        model = new DefaultTableModel();
        table.setModel(model);
        model.addColumn("Months");

        JScrollPane sp = new JScrollPane(table);

        setLayout(new BorderLayout());

        add(sp, BorderLayout.CENTER);
        add(button, BorderLayout.SOUTH);
        add(mp, BorderLayout.NORTH);
        setSize(800, 600);

        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                Month();
                Object[] row = {Months};

                model.addRow(row);
            }
        });

    }

    public void Month() {
        Months.removeAll(Months);
        if (chkJan.isSelected()) {
            Months.add("January");
        } else {
            Months.remove("January");
        }

        if (chkFeb.isSelected()) {
            Months.add("Febuary");
        } else {
            Months.remove("Febuary");
        }

        if (chkMarch.isSelected()) {
            Months.add("March");
        } else {
            Months.remove("March");
        }

        if (chkApril.isSelected()) {
            Months.add("April");
        } else {
            Months.remove("April");
        }

        if (chkMay.isSelected()) {
            Months.add("May");
        } else {
            Months.remove("May");
        }

        if (chkJun.isSelected()) {
            Months.add("Jun");
        } else {
            Months.remove("Jun");
        }

        if (chkJuly.isSelected()) {
            Months.add("July");
        } else {
            Months.remove("July");
        }

        if (chkAug.isSelected()) {
            Months.add("August");
        } else {
            Months.remove("August");
        }

        if (chkSep.isSelected()) {
            Months.add("September");
        } else {
            Months.remove("September");
        }

        if (chkOct.isSelected()) {
            Months.add("Octuber");
        } else {
            Months.remove("Octuber");
        }

        if (chkNov.isSelected()) {
            Months.add("November");
        } else {
            Months.remove("November");
        }

        if (chkDec.isSelected()) {
            Months.add("December");
        } else {
            Months.remove("December");
        }
    }

    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;

                }
            }
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Jtable.class
                    .getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Jtable().setVisible(true);
            }
        });
    }

}

Answer 1

你的问题是Months是全局的，你要的是局部变量。如果你在某处编辑这个变量，每个使用它的对象（比如行或你 table）都会反映它的变化。

您可以将 Months 移动到您的方法中您只能本地访问的某个位置，如下所示：

button.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        model.addRow(Months());
    }
});

然后，修改你的Month方法：

public Object[] Month() {
    List<String> Months = new ArrayList<>();
    if (chkJan.isSelected()) {
        Months.add("January");
    } else ...
    ...
    return new Object[]{Months};
}

另一件事，用小写 Months 命名变量是一个好习惯，可以是 months，并将方法命名为更易读的东西，例如 getSelectedMonths 最后，令人困惑将您的 class 命名为 Jtable，因为还有另一个名称相似 (JTable)。

编辑

再次查看，我猜你的很多代码是多余的，你可以去掉优化，因为你只需要 Month returns.

Answer 2

改变

public void Month() {
        Months.removeAll(Months);
        ...

收件人：

public void Month() {
        Months = new ArrayList<>();
        ...

这样您就不会修改已经存储在 table 中的月份。

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