将图片从数据库加载到JTable

Question

我想将数据库中的某些图片加载到jTable中，为此我正在使用渲染器，这是jFrame的当前代码：

package projet.ihm;

import java.awt.Component;
import java.awt.Image;
import static java.sql.DriverManager.println;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JTable;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;

public class ListeCours extends javax.swing.JFrame {
    Statement stmtconsulter;
    connection maco = new connection();
    DefaultTableModel model = new DefaultTableModel();
    ImageIcon img;
    int i = 0;
    /**
     * Creates new form ListeCours
     */
    public ListeCours() {
        initComponents();
        model.addColumn("id");
        model.addColumn("image");
        model.addColumn("Description courte");
        jTable1.setModel(model);
        jTable1.setRowHeight(100);
        String consulter = "select *from load_cours";
        try {
            stmtconsulter = maco.getConnection().createStatement();
            ResultSet Rs = stmtconsulter.executeQuery(consulter);
            while (Rs.next()) {
                if (Rs.getBytes(4) != null) {
                    ImageIcon image = new ImageIcon(new ImageIcon(Rs.getBytes(4)).getImage().getScaledInstance(150, 120, Image.SCALE_SMOOTH));
                    img = image;
                    Renderer renderer = new Renderer(img);
                    jTable1.getColumnModel().getColumn(1).setCellRenderer(renderer);
                } else {
                    img = null;
                }
                Object[] c = {Rs.getInt(1),"",Rs.getString(2)};
                model.addRow(c);
                i = i + 1;
            }
        } catch (SQLException ex) {
            System.out.println(ex);
        }
    }

    class Renderer extends DefaultTableCellRenderer {
        private final ImageIcon icon;
        public Renderer(ImageIcon icon) {
            super();
            this.icon = icon;
        }
        @Override
        public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
            super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
            setIcon((row == i) ? icon : null);
            // Ou setIcon((value <test sur la valeur ici>)  ? icon : null);
            return this;
        }
    }
    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        jPanel1.setBackground(new java.awt.Color(255, 255, 255));
        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object[][] {
                {null,null,null},{null,null,null},{null,null,null},
                {null,null,null},{null,null,null}
            },
            new String[] {"Title 1","Title 2","Title 3"}
        ) {
            boolean[] canEdit = new boolean[] {false,false,false};
            public boolean isCellEditable(int rowIndex, int columnIndex) {
                return canEdit[columnIndex];
            }
        });
        jScrollPane1.setViewportView(jTable1);
        if (jTable1.getColumnModel().getColumnCount() > 0) {
            jTable1.getColumnModel().getColumn(0).setResizable(false);
            jTable1.getColumnModel().getColumn(1).setResizable(false);
            jTable1.getColumnModel().getColumn(2).setResizable(false);
        }
        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(20, 20, 20)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 633, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(269, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(34, 34, 34)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 482, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(117, Short.MAX_VALUE))
        );
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        pack();
    } // </editor-fold>                        

    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 ex) {
            java.util.logging.Logger.getLogger(ListeCours.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ListeCours.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ListeCours.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ListeCours.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 ListeCours().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    // End of variables declaration                   
}

问题似乎出在我在渲染器代码中使用的关键条件：

setIcon((row == i)  ? icon : null);

当我将row == i放进去时，根本没有图像加载，但是如果我尝试像row == 2这样的东西，它将在我的图片列的第2行的1个单元格中加载图像。我不明白为什么它不适用于row == i，因为我需要填写图片列的所有单元格。

我还通过将所有图像存储在ImageIcon [] img中并且仅使用渲染器一次来尝试了一些不同的东西，但是启动程序时出现异常，这是有问题的代码：

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package projet.ihm;

import java.awt.Component;
import java.awt.Image;
import static java.sql.DriverManager.println;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JTable;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;



public class ListeCours extends javax.swing.JFrame {
Statement stmtconsulter;
connection maco = new connection();
DefaultTableModel model = new DefaultTableModel();
ImageIcon[] img;
int i = 0;
    /**
     * Creates new form ListeCours
     */
    public ListeCours() {
        initComponents();
        model.addColumn("id");
        model.addColumn("image");
        model.addColumn("Description courte");
        jTable1.setModel(model);
        jTable1.setRowHeight(100);
        String consulter = "select *from load_cours";
        try {
            stmtconsulter = maco.getConnection().createStatement();
            ResultSet Rs = stmtconsulter.executeQuery(consulter);
            while(Rs.next()) {
               if(Rs.getBytes(4) != null){
               ImageIcon image = new ImageIcon(new ImageIcon(Rs.getBytes(4)).getImage().getScaledInstance(150, 120, Image.SCALE_SMOOTH) );  
               img[i] = image;


            }
            else{
                img[i] = null;
            }
            Object [] c ={Rs.getInt(1),"",Rs.getString(2)};
            model.addRow(c);
            i=1;
            }


        }
        catch(SQLException ex){
            System.out.println(ex);
        }
      jTable1.getColumnModel().getColumn(1).setCellRenderer(new Renderer());
    }

    class Renderer extends DefaultTableCellRenderer
    {
  JLabel lbl = new JLabel();

  @Override
  public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) 
  {
      lbl.setIcon(img[row]);
      return lbl;
  }
}

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jPanel1.setBackground(new java.awt.Color(255, 255, 255));

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null},
                {null, null, null},
                {null, null, null},
                {null, null, null},
                {null, null, null}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3"
            }
        ) {
            boolean[] canEdit = new boolean [] {
                false, false, false
            };

            public boolean isCellEditable(int rowIndex, int columnIndex) {
                return canEdit [columnIndex];
            }
        });
        jScrollPane1.setViewportView(jTable1);
        if (jTable1.getColumnModel().getColumnCount() > 0) {
            jTable1.getColumnModel().getColumn(0).setResizable(false);
            jTable1.getColumnModel().getColumn(1).setResizable(false);
            jTable1.getColumnModel().getColumn(2).setResizable(false);
        }

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(20, 20, 20)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 633, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(269, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(34, 34, 34)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 482, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(117, Short.MAX_VALUE))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );

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

    /**
     * @param args the command line arguments
     */
    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 ex) {
            java.util.logging.Logger.getLogger(ListeCours.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ListeCours.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ListeCours.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ListeCours.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 ListeCours().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    // End of variables declaration                   
}

这是我得到的例外：

That's the exception i'm actually getting : 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at projet.ihm.ListeCours.<init>(ListeCours.java:49)
    at projet.ihm.ListeCours$2.run(ListeCours.java:186)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)