Java 表系统不工作

Question

我对 Java 完全陌生，并且被分配了一项任务，我们必须创建一个图书库系统。该表必须有 7 列。但是我目前只能得到 2，然后代码就停止工作了。在下面的示例中，我尝试获取 3 列，但也失败了。有人能发现错误或我遗漏的任何内容吗？当运行表而不是数据时，它显示 [Ljava.lang.Object;@3dda9c8b

import javax.swing.JOptionPane;
import javax.swing.table.DefaultTableModel;

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/

/**
*
* @author Mark
*/
public class BookDatabase_frame extends javax.swing.JFrame {


        Object [][][] data = null;
        String [] columnNames = new String [3];
/**
 * Creates new form BookDatabase_frame
 */
public BookDatabase_frame() {
    initComponents();
}

/**
 * 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() {

    jScrollPane1 = new javax.swing.JScrollPane();
    jTable1 = new javax.swing.JTable();
    jButton1 = new javax.swing.JButton();
    jButton2 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
    getContentPane().setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());

    jTable1.setModel(new javax.swing.table.DefaultTableModel(
        new Object [][] {
            {null, null, null, null},
            {null, null, null, null},
            {null, null, null, null},
            {null, null, null, null}
        },
        new String [] {
            "Title 1", "Title 2", "Title 3", "Title 4"
        }
    ));
    jScrollPane1.setViewportView(jTable1);

    getContentPane().add(jScrollPane1, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 80, 375, 275));

    jButton1.setText("Initiate table");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });
    getContentPane().add(jButton1, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 40, -1, -1));

    jButton2.setText("Add row");
    getContentPane().add(jButton2, new org.netbeans.lib.awtextra.AbsoluteConstraints(110, 40, -1, -1));

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

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        columnNames = new String [] {"Name", "Country","age"};
        data = new Object [1][2][3];
        data [0][0][0]= JOptionPane.showInputDialog("Enter your Name");
        data [0][1][0] = JOptionPane.showInputDialog("Enter your country");
        data [0][0][2] = JOptionPane.showInputDialog("Enter your age");


        jTable1.setModel(new DefaultTableModel(data, columnNames));
}                                        

/**
 * @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(BookDatabase_frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(BookDatabase_frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(BookDatabase_frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(BookDatabase_frame.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 BookDatabase_frame().setVisible(true);
        }
    });
}
// Variables declaration - do not modify                     
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTable jTable1;
// End of variables declaration                   
}

Answer 1

"The table must have 7 columns. however I can only currently get 2 and then the code stops working.

如果您想要 7 列，则让列名数组有 7 个字符串。

对于行，您只需要一维数组，而不是双维或三元数组。并将 actionPerformed 中的每一行单独添加到模型中。只需使用 0 行和列名称初始化模型即可。

String colNames = {"1", "2", "3", "4", "5", "6", "7"};
DefaultTableModel model = new DefaultTableModel(colNames, 0);  <-- 0 rows

....

public void actionPerformed(ActionEvent e){
    // get 7 fields of data

    Object[] row = {data1, data2, data3, data4, data5, data6, data7};
    model.addRow(row);
}

我假设您不希望所有数据最初都位于 JTable 中，并且您希望每次按下按钮时都能够添加新数据。所以你需要做的是在actionPerformed之外初始化模型和表格，并且每次按下按钮时，获取所有7条数据，将它们放入一个数组中，然后将该数组添加到模型中，这将自动在表格中添加另一行

<小时/>

来自 Netbeans GUI 生成器

• 突出显示表格图形
• 转到“属性面板”(您应该会在屏幕的最右侧看到它)
• 转到显示模型广告的属性，然后单击...按钮
• 将行设置为 0

在你的actionPerformed中只需做这样的事情

public void actionPerformed(ActionEvent e){
    // get 7 fields of data

    Object[] row = {data1, data2, data3, data4, data5, data6, data7};
    ((DefaultTableModel)jTable1.getModel()).addRow(row);
}