java - 范围混淆(对我来说): DefaultTableModel keeps reference to Vector. 为什么？

Question

只有 loadDefaultTableModel 中 rowData 的最后一个 Vector 实例实际上显示在实际的 JTable 中。这是为什么？

其他 vector 和其他数据正在被实例化，但显然没有添加到模型中。至少它们没有被显示出来。

如何确保模型包含所需数据？所需的数据由Logger 输出，并且已经是Vector 形式。我不明白这种矛盾。

package net.bounceme.dur.nntp.swing;

import java.util.Map;
import java.util.Map.Entry;
import java.util.Vector;
import java.util.logging.Logger;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
import net.bounceme.dur.nntp.gnu.PageMetaData;
import net.bounceme.dur.nntp.gnu.Page;
import net.bounceme.dur.nntp.gnu.Usenet;

public class ArticlesTable extends JScrollPane {

    private static final Logger LOG = Logger.getLogger(ArticlesTable.class.getName());
    private static final long serialVersionUID = 1L;
    private JTable jTable = new JTable();
    private DefaultTableModel defaultTableModel = new DefaultTableModel();
    private Page page;
    private Usenet usenetConnection = Usenet.INSTANCE;

    public ArticlesTable() throws Exception {
        page = new Page();//eh, throws Exception -- fix later
        LOG.fine(page.toString());  //empty Page
        initComponents();
    }

    @SuppressWarnings("unchecked")
    private void initComponents() {
        defaultTableModel = new DefaultTableModel(new Object[][]{
                    {"some", "text"}, {"any", "text"}, {"even", "more"},
                    {"text", "strings"}, {"and", "other"}, {"text", "values"}},
                new Object[]{"Column 1", "Column 2"});
        jTable.setModel(defaultTableModel);
        jTable.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
        jTable.addMouseListener(new java.awt.event.MouseAdapter() {

            public void mouseReleased(java.awt.event.MouseEvent evt) {
                itemSelected();
            }
        });
        jTable.addKeyListener(new java.awt.event.KeyAdapter() {

            public void keyReleased(java.awt.event.KeyEvent evt) {
                itemSelected();
            }
        });

        setSize(2000, 2000);  //not sure these lines are quite right, but ok for now
        setViewportView(jTable);
        jTable.setVisible(true);
        setVisible(true);
    }

    private void itemSelected() {
        int row = jTable.getSelectedRow();
        int column = 0;
        Object selectedObject = jTable.getValueAt(row, column);
        int i = (int) selectedObject;
        Map<Integer, Message> messages = page.getMessages();
        Message message = messages.get(i);
        firePropertyChange("message", null, message);
    }

    public final void nextPage() throws Exception {
        LOG.fine("trying to get next page..." + page);
        PageMetaData pageMetaData = page.getPageMetaData();
        pageMetaData.next();  //only changes meta data
        page = usenetConnection.getPage(pageMetaData); //fetches actual data
        LOG.fine("was the page advanced?" + page);  //yes, logs show this
        loadDefaultTableModel();
        LOG.fine(page.toString());
    }

    @SuppressWarnings("unchecked")
    private void loadDefaultTableModel() throws MessagingException {
        LOG.fine("trying to load...");
        defaultTableModel = new DefaultTableModel();
        defaultTableModel.addColumn("index");
        defaultTableModel.addColumn("message subject");
        Vector rowData = new Vector(); //vector?! nothing better?
        Message message = null;
        Map<Integer, Message> messages = page.getMessages(); //sort this
        int key = 0;
        LOG.info("trying to traverse..." + messages.size()); //page meta data determines the size
        for (Entry<Integer, Message> entry : messages.entrySet()) {
            rowData.clear();
            key = entry.getKey();
            message = messages.get(key);
            rowData.add(key);
            rowData.add(message.getSubject());
            LOG.info("vector\t" + key + "\t" + message.getSubject());
            //the vector logs the data which **should** get added
            //to the table model
            defaultTableModel.addRow(rowData);  //adds same row over and over
        }
        jTable.setModel(defaultTableModel);
    }

    private Message getMessage(int i) {
        LOG.fine("trying to get\t\t" + i);
        Map<Integer, Message> messages = page.getMessages();
        Message m = messages.get(i);
        return m;
    }
}

图片:

和一些输出:

INFO: trying to traverse...5
Apr 15, 2013 2:05:13 AM net.bounceme.dur.nntp.swing.ArticlesTable loadDefaultTableModel
INFO: vector    25  Re: Netbeans question?
Apr 15, 2013 2:05:13 AM net.bounceme.dur.nntp.swing.ArticlesTable loadDefaultTableModel
INFO: vector    27  Re: Helpppp plzzz
Apr 15, 2013 2:05:13 AM net.bounceme.dur.nntp.swing.ArticlesTable loadDefaultTableModel
INFO: vector    26  Re: writing Unix files on Windows
Apr 15, 2013 2:05:13 AM net.bounceme.dur.nntp.swing.ArticlesTable loadDefaultTableModel
INFO: vector    29  JTextPane.modelToView() exception
Apr 15, 2013 2:05:13 AM net.bounceme.dur.nntp.swing.ArticlesTable loadDefaultTableModel
INFO: vector    28  Java 6 update 39 to 41 balloon

可以看出，每个 vector 实例都有正确的数据。但是，似乎只有第一个实例出现在 GUI 输出中。为什么？

它没有正确添加到模型中吗？模型是否没有正确更新表格？

为什么在 GUI 中看到的模型中的数据与记录的输出不匹配？

Answer 1

How do I ensure that the model contains the desired data?

DefaultTableModel 是内部使用 Vector 的 TableModel 的基本实现。 Vector 是一个同步的遗留类，它使用 System.arraycopy() 广泛。

由于您可能需要更好地控制内部数据结构，AbstractTableModel 提供了所需的事件管道并让您直接管理数据结构。

Creating a Table Model比较这两种方法，这 example说明 Map 可能暗示了好处。