JTable单元格返回null [英] JTable cell returning null

问题描述

我在 JTable 单元格内使用 JTextField ;我使用 TabelModel ，其中包含 JTable 的动态数据。现在，当我点击一个按钮时，我正在读取一个单元格值。
问题是具有当前焦点的单元格不返回更新的值。例如，请考虑以下程序：

I am using JTextField inside JTable cells; I use a TabelModel which has the dynamic data of the JTable. Now, when I click a button, I am reading a cell value. Problem is the cell which has the present focus doesn't return the updated value. For example, consider this program:

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableCellRenderer;

public class MyTable extends JFrame {

    DefaultTableModel tmodel = new DefaultTableModel(new Object[][]{
            {"some"}, {"any"}, {"even"}, {"text"}, {"and"}, {""}},
        new Object[]{"Column 1"});

    public MyTable() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final JTable table = new JTable(tmodel);
        table.setDefaultRenderer(Object.class, new MyRenderer());
        getContentPane().add(new JScrollPane(table), BorderLayout.CENTER);
        getContentPane().setLayout(new GridLayout(2, 2));
        JButton jb = new JButton("click me"); //button to display last cell data
        jb.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent arg0) {
                JOptionPane.showMessageDialog(
                    null, table.getModel().getValueAt(5, 0));
            }
        });
        getContentPane().add(jb);
    }

    public static void main(String arg[]) {
        new MyTable().setVisible(true);
    }
}

class MyRenderer implements TableCellRenderer {

    public Component getTableCellRendererComponent(JTable table, Object value,
        boolean isSelected, boolean hasFocus, int row, int column) {
        JTextField editor = new JTextField();
        if (value != null) {
            editor.setText(value.toString());
        }
        return editor;
    }
}

这里我将最后一个字段留空。当我读它时

Here I am leaving the last field empty. When I read it by

table.getModel().getValueAt(5, 0)

我得到 null 。现在我将值更改为5,0，再次单击按钮，但现在我再次获得 null 。现在令人惊讶的是，我编辑了一些其他单元格，再次单击按钮;现在我在5,0单元得到了正确的数据！为什么是这样？这是一个错误吗？我尝试了几种可能性！

I get null. Now I change the value at 5,0, and again click the button, but now again I get null. Now surprisingly, I edit some other cell, again click button; now I get the correct data at cell 5,0! Why is this? Is this a bug? I tried several possibilities!

推荐答案

合并@ kleopatra的建议和@ mKorble有用的修订，这里有一些基于您的示例的其他想法。请特别注意使用 setDefaultButton（）和 行动 与 键绑定 。

Incorporating @kleopatra's suggestion and @mKorble's helpful revisions, here are a few additional ideas based on your example. Note in particular the use of setDefaultButton() and Action in conjunction with Key Bindings.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.KeyStroke;
import javax.swing.table.DefaultTableModel;

/** @see https://stackoverflow.com/q/9874664/230513 */
public class MyTable extends JFrame {

    private static final String show = "Show";
    private DefaultTableModel tmodel = new DefaultTableModel(
        new Object[][]{
            {"edit"}, {"any"}, {"cell"}, {"text"}, {"and"}, {"edit me"}},
        new Object[]{
            "Column 1"});
    private JTable table = new JTable(tmodel);
    private Action showAction = new ShowAction(show);
    private JButton jb = new JButton(showAction);

    public MyTable() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationByPlatform(true);
        table.putClientProperty("terminateEditOnFocusLost", true);
        KeyStroke enter = KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0);
        table.getInputMap(JTable.WHEN_FOCUSED).put(enter, show);
        table.getActionMap().put(show, showAction);
        add(new JScrollPane(table), BorderLayout.CENTER);
        table.setPreferredScrollableViewportSize(new Dimension(400, 200));
        JPanel panel = new JPanel();
        panel.add(jb);
        getRootPane().setDefaultButton(jb);
        add(panel, BorderLayout.SOUTH);
        pack();
    }

    private class ShowAction extends AbstractAction {

        private ShowAction(String name) {
            super(name);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            if (table.isEditing()) {
                table.getCellEditor().stopCellEditing();
            }
            int row = table.getSelectedRow();
            if (row > -1) {
                JOptionPane.showMessageDialog(
                    MyTable.this, table.getModel().getValueAt(row, 0));
            }
        }
    }

    public static void main(String arg[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new MyTable().setVisible(true);
            }
        });
    }
}

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