Question

所以我是java和netbeans的新手，但是我编写了一个代码来从数据库中加载一些数据并在JTable中显示它，当我几天前做它时工作得很好并且显示了所有内容然而，当我今天打开它时它不显示任何东西，我真的不知道为什么，我几乎检查了一切。这是代码：

注意：我上传了所有代码，以防需要，但您应该检查执行插入的按钮btnLoad的方法。

package cinemaohadid;
import java.awt.Component;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.*;
import javax.swing.JOptionPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableColumn;

public class AllMovies extends javax.swing.JFrame {


public AllMovies() {
    initComponents();
}

@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jPanel1 = new javax.swing.JPanel();
    jScrollPane1 = new javax.swing.JScrollPane();
    tblAllMovies = new javax.swing.JTable();
    btnLoad = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle("Watch All Movies");

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 0, Short.MAX_VALUE)
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 325, Short.MAX_VALUE)
    );

    tblAllMovies.setModel(new javax.swing.table.DefaultTableModel(
        new Object [][] {

        },
        new String [] {
            "ID", "Title", "Genre", "Show Time"
        }
    ) {
        Class[] types = new Class [] {
            java.lang.Integer.class, java.lang.String.class, java.lang.String.class, java.lang.Object.class
        };
        boolean[] canEdit = new boolean [] {
            false, false, false, false
        };

        public Class getColumnClass(int columnIndex) {
            return types [columnIndex];
        }

        public boolean isCellEditable(int rowIndex, int columnIndex) {
            return canEdit [columnIndex];
        }
    });
    tblAllMovies.setPreferredSize(new java.awt.Dimension(400, 0));
    jScrollPane1.setViewportView(tblAllMovies);
    tblAllMovies.getColumnModel().getSelectionModel().setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
    if (tblAllMovies.getColumnModel().getColumnCount() > 0) {
        tblAllMovies.getColumnModel().getColumn(0).setMinWidth(20);
        tblAllMovies.getColumnModel().getColumn(0).setPreferredWidth(20);
        tblAllMovies.getColumnModel().getColumn(1).setPreferredWidth(200);
        tblAllMovies.getColumnModel().getColumn(2).setPreferredWidth(60);
        tblAllMovies.getColumnModel().getColumn(3).setResizable(false);
        tblAllMovies.getColumnModel().getColumn(3).setPreferredWidth(120);
    }

    btnLoad.setText("Load");
    btnLoad.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnLoadActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 488, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(btnLoad)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addComponent(jPanel1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                .addComponent(btnLoad)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 275, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void btnLoadActionPerformed(java.awt.event.ActionEvent evt) {                                        
    String user = "aa";
    String pass = "aa";
    String host = "jdbc:derby://localhost:1527/Results";

    DefaultTableModel dtm = (DefaultTableModel) tblAllMovies.getModel();
    Connection con;
    try {
        con = DriverManager.getConnection(host, user, pass);
        Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
        String SQL = "SELECT * FROM Movies";
        ResultSet rs = stmt.executeQuery(SQL);
        int rowcount=-1;
        while (rs.next()) {
            rowcount++;
            int movieID = rs.getInt("MOVIEID");
            String movieName = rs.getString("MOVIENAME");
            Timestamp movieTime = rs.getTimestamp("MOVIETIME");
            String movieGenre = rs.getString("MOVIEGENRE");
            dtm.addRow(new Object[]{movieID,movieName ,movieGenre ,movieTime});
        }
        dtm.fireTableDataChanged();
        stmt.close();
        rs.close();
    } catch (SQLException err) {
        System.out.println(err.getMessage());
    }
    //btnLoad.setVisible(false);

}                                       

public static void main(String args[]) {

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








    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new AllMovies().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton btnLoad;
private javax.swing.JPanel jPanel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTable tblAllMovies;
// End of variables declaration                   
}

Answer 1

关闭结果集后，您是否尝试在pack();方法中加入btnLoadActionPerformed？您似乎在告诉表格其值已更改但未更新图形元素。

对于它的价值，我就是这样做的。首先创建一个扩展默认表模型的新类：

class MovieTableModel extends DefaultTableModel {

    private static boolean[] canEdit = new boolean[] {false, false, false, false};

    public MovieTableModel() {
        super();
    }

    public boolean isCellEditable(int rowIndex, int columnIndex) {
        return canEdit[columnIndex]; // or just return false if it's always going to be false
    }
}

然后将btnLoadActionPerformed更改为

private void btnLoadActionPerformed(java.awt.event.ActionEvent evt) {                                        
    String user = "aa";
    String pass = "aa";
    String host = "jdbc:derby://localhost:1527/Results";

    Connection con;
    try {
        con = DriverManager.getConnection(host, user, pass);
        Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
        String SQL = "SELECT * FROM Movies";
        ResultSet rs = stmt.executeQuery(SQL);

        MovieTableModel mtm = new MovieTableModel();
        mtm.addColumn("ID");
        mtm.addColumn("Title");
        mtm.addColumn("Genre");
        mtm.addColumn("Show Time");

        Vector<Object> row;

        while (rs.next()) {
            row = new Vector<Object>();

            row.add(rs.getInt("MOVIEID"));
            row.add(rs.getString("MOVIENAME"));
            row.add(rs.getTimestamp("MOVIETIME"));
            row.add(rs.getString("MOVIEGENRE"));

            mtm.addRow(row);
        }

        tblAllMovies = new JTable(mtm);
        stmt.close();
        rs.close();
        pack();
    } catch (SQLException err) {
        System.out.println(err.getMessage());
    }
}

我希望这有帮助！

== EDIT ==

更新了使用向量而不是数组来填充表格的方法。

Answer 2

你可以编辑代码或给我一个代码，在我的代码中替换什么

//dtm.addRow(new Object[]{movieID,movieName ,movieGenre ,movieTime});
Vector<Object> row = new Vector<Object>();
row.addElement(movieID);
row.addElement(movieName);
row.addElement(movieGenre);
row.addElement(movieTime);

关于索引的评论是针对moarCoffee发布的示例。 Vector只是按顺序添加对象，因此您无需担心对索引进行硬编码。

此外，此建议无法解决您的问题。

编辑：

发布SSCCE的目的是简化代码。我们无权访问您的数据库，因此无法运行代码。所以你的SSCCE应该是演示问题的代码。这是通过删除SQL逻辑而不是使用：

来完成的

private void btnLoadActionPerformed(java.awt.event.ActionEvent evt)
{
    DefaultTableModel dtm = (DefaultTableModel) tblAllMovies.getModel();
    dtm.addRow( new Object[]{new Integer(1), "movieName1" , "movieGenre1", "movieTime1"} );
    dtm.addRow( new Object[]{new Integer(2), "movieName2" , "movieGenre2", "movieTime2"} );
    dtm.addRow( new Object[]{new Integer(3), "movieName3" , "movieGenre3", "movieTime3"} );
    dtm.addRow( new Object[]{new Integer(4), "movieName4" , "movieGenre4", "movieTime4"} );
}

确实问题仍然存在，因此验证问题不在于SQL。

接下来，我看一下IDE生成的所有垃圾代码来进行布局。果然我找到了以下一行：

tblAllMovies.setPreferredSize(new java.awt.Dimension(400, 0));

当我注释掉那条线时，它起作用了。使用Swing时不要使用setPreferredSize()方法。

另一个建议是不要使用IDE来生成布局代码。代码是不可理解的，如果您移动到另一个IDE，则无法移植。

布局可以用几行代码完成：

JScrollPane scrollPane = new JScrollPane(table);
frame.add(scrollPane, BorderLayout.CENTER);

Box east = Box.CreateVerticalBox();
east.add(Box.createVerticalGlue());
east.add(button);
frame.add(east, BorderLayout.LINE_END);

相反，它比IDE生成的所有代码更简单，更容易理解。你可以轻松地自定义上面的内容，添加一些Borders，使其看起来完全符合另外两行代码的需要。

JTable在插入后不会显示数据

2 个答案: