是否可以使用数据库中的相似名称打开文件？

Question

因此，当我单击按钮 ("Open Lesson") 时，将出现来自不同 class 的 JFrame（使用 .setVisible(true)）。在该 JFrame 中有一个 JTable (tblOpenLesson) 和两个按钮（btnOpenLesson 和 btnCancel）。

现在我想要发生的是，当我单击打开课程按钮时，它将执行以下操作： 1. 更新 table 以将 sqlite 数据库（课程）反映到 JTable 中 2. 打开通过获取文件名（与数据库中的相同）并将其用于 FileReader 函数，从 table 中选择文件。

但是，它给我错误：

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: -1 at java.util.Vector.elementData(Vector.java:737) at java.util.Vector.elementAt(Vector.java:480) at javax.swing.table.DefaultTableModel.getValueAt(DefaultTableModel.java:648) at mainWindow.openLesson.btnOpenLessonPopUpActionPerformed(openLesson.java:135) at mainWindow.openLesson.access[=11=]0(openLesson.java:19) at mainWindow.openLesson.actionPerformed(openLesson.java:60) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) at java.awt.Component.processMouseEvent(Component.java:6539) at javax.swing.JComponent.processMouseEvent(JComponent.java:3324) at java.awt.Component.processEvent(Component.java:6304) at java.awt.Container.processEvent(Container.java:2239) at java.awt.Component.dispatchEventImpl(Component.java:4889) at java.awt.Container.dispatchEventImpl(Container.java:2297) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476) at java.awt.Container.dispatchEventImpl(Container.java:2283) at java.awt.Window.dispatchEventImpl(Window.java:2746) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760) at java.awt.EventQueue.access0(EventQueue.java:97) at java.awt.EventQueue.run(EventQueue.java:709) at java.awt.EventQueue.run(EventQueue.java:703) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84) at java.awt.EventQueue.run(EventQueue.java:733) at java.awt.EventQueue.run(EventQueue.java:731) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74) at java.awt.EventQueue.dispatchEvent(EventQueue.java:730) 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)

我尝试搜索应该如何修复它，但我被困在这里 3 天无济于事。

这是弹出 JFrame 的代码：

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

private void btnCancelOpenLessonActionPerformed(java.awt.event.ActionEvent evt) {                                                    
    this.setVisible(false);
}                                                   

private void btnOpenLessonPopUpActionPerformed(java.awt.event.ActionEvent evt) {                                                   

    updateDBlessons(); // update list

    String[] fileName = null;

    int selectedColumn = tblOpenLesson.getSelectedColumn();
    int selectedRow = tblOpenLesson.getSelectedRow();
    try {
        Class.forName("org.sqlite.JDBC");
        Connection con = DriverManager.getConnection("jdbc:sqlite:sql_items.sqlite");
        Statement stmtGetLesson = con.createStatement();
        ResultSet rs = stmtGetLesson.executeQuery("SELECT * FROM lessons WHERE lesson_id  = '" + tblOpenLesson.getModel().getValueAt(selectedRow, selectedColumn) + "';");

        if (rs.next()) {
            fileName[0] = rs.getString("lesson");
        }
    } catch (SQLException e) {
        JOptionPane.showMessageDialog(null, e);
    } catch (ClassNotFoundException ex) {
        Logger.getLogger(openLesson.class.getName()).log(Level.SEVERE, null, ex);
    }

        try {
        FileReader fr = new FileReader("Lessons\" + fileName[0] + ".txt");
            try (BufferedReader br = new BufferedReader(fr)) {
            mainScreen.lessonPane.read(br, null); //  lessonPane is from another class
            br.close();
            }
        } catch (IOException e) {
        System.out.println(e);
        this.setVisible(false);
        }


}                                                  


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 
     */

    //</editor-fold>

    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(() -> {
        new openLesson().setVisible(false);
    });
}

public void updateDBlessons() {
    try {
        Class.forName("org.sqlite.JDBC");
        Connection  con = DriverManager.getConnection("jdbc:sqlite:sql_items.sqlite");
        Statement stmt = con.createStatement();
        ResultSet rs = stmt.executeQuery("SELECT * FROM lessons");
        DefaultTableModel dtm = (DefaultTableModel) tblOpenLesson.getModel();
        dtm.setRowCount(0);

        while(rs.next()){
            Object o[] = {rs.getString("lesson")};
            dtm.addRow(o);
        }
    } catch (ClassNotFoundException | SQLException e) {

    }
}


// Variables declaration - do not modify                     
private javax.swing.JButton btnCancelOpenLesson;
private javax.swing.JButton btnOpenLessonPopUp;
private javax.swing.JLabel jLabel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JPanel pnlOpenLesson;
private javax.swing.JTable tblOpenLesson;
// End of variables declaration

}

我开始认为这是不可能的。如果是这样，请告诉我我能做什么。非常感谢

Answer 1

在 getSelectedColumn()/getSelectedRow() 之前调用 updateDBlessons() 会将选定的 row/column 重置为 -1。

不要在 btnOpenLessonPopUpActionPerformed 中调用 updateDBlessons()，而是在显示 JFrame 之前调用它。

是否可以使用数据库中的相似名称打开文件？

Is it possible to open a file using a similar name from a database?

java

sqlite

filereader