Question

我想创建一个在线考试项目。我点击下一步它应该在textarea中显示下一个数据。但问题是当我点击提交按钮时它会显示数据库中的最后一个数据。 while（rs.next（））打印文本框中的最后一个值。

    import java.awt.BorderLayout;

    import java.awt.GridLayout;

    import java.awt.event.ActionEvent;

    import java.awt.event.*;

    import javax.swing.*;

    import java.sql.*;

    import java.awt.*;

    import java.util.*;



    class Abc extends JFrame implements ActionListener{

    JLabel l1,l2,l3,l4;
    JButton b1,b2; 
    JTextArea j1,j2;
    JCheckBox c1,c2,c3,c4;
    ButtonGroup group=new ButtonGroup();

    JPanel panel2;
    Abc(){  
       j1=new JTextArea();
       j2=new JTextArea();
       c1=new JCheckBox();
       c2=new JCheckBox();
       c3=new JCheckBox();
       c4=new JCheckBox();
       j1.setEditable(false);
       c1.setSelected(false);
       c2.setSelected(false);
       c3.setSelected(false);
       c4.setSelected(false);

       group.add(c1);
       group.add(c2);
       group.add(c3);
       group.add(c4);

       Connection conn=null;
       try{  
           Class.forName("oracle.jdbc.driver.OracleDriver");
         conn=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","system","java");
         System.out.println("Dc is obtained");

          }
       catch(Exception e2){
        System.out.println("conne"+e2.getMessage());
          } 
       try{
          String sq="select * from questionans";
          Statement st=conn.createStatement();
          ResultSet rs=st.executeQuery(sq);
          System.out.println("------------------------------------------");
          if(rs.next())
          {

           j1.setText(rs.getString(2));
           c1.setText(rs.getString(3));
           c2.setText(rs.getString(4));
           c3.setText(rs.getString(5));
           c4.setText(rs.getString(6));
          }
          System.out.println("-------------------------------------------");        
          }
          catch(Exception e1){
            System.out.println("query" +e1.getMessage());
          }
         finally{
            try {
              conn.close();
                }
          catch(Exception e)
             {
             System.out.println("close conn"+e.getMessage());     
             } 
           }








        b1=new JButton("REGISTER");
        b2=new JButton("SUBMIT"); 
        panel2=new JPanel(new GridLayout(4,1)); 
        panel2.add(b1);
        panel2.add(j1);
        panel2.add(c1);
        panel2.add(c2);
        panel2.add(c3);
        panel2.add(c4);
        panel2.add(b2); 

        add(panel2,BorderLayout.CENTER); 
        b1.addActionListener(this); 
        b2.addActionListener(this);
        setTitle("REGISTRATION"); 

        } 
        public void actionPerformed(ActionEvent e) {
            Object source=e.getSource();
            if(source==b1)
             {
              System.out.println("you pressed button b1");
              }
              else if(source==b2)
              {  

               Connection conn=null;

              try{  
                  Class.forName("oracle.jdbc.driver.OracleDriver");
         conn=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","system","java");
                  System.out.println("Dc is obtained");

                  }
             catch(Exception e4){
                    System.out.println("conne"+e4.getMessage());
                  }
               try{
                   String sq="select * from questionans";
                   Statement st=conn.createStatement();
                   ResultSet rs=st.executeQuery(sq);
                   System.out.println("------------------------------------------");



                 while(rs.next()){

                    j1.setText(rs.getString(2));
                    c1.setText(rs.getString(3));
                    c2.setText(rs.getString(4));
                    c3.setText(rs.getString(5));
                    c4.setText(rs.getString(6));

                   }



                    System.out.println("-------------------------------------------");        
                   }
            catch(Exception e3){
                    System.out.println("query" +e3.getMessage());
                    }
            finally{
                    try{
                        conn.close();
                        }
            catch(Exception e6)
                   {
                    System.out.println("close conn"+e6.getMessage());     
                    } 
                  }

             String s2="";
             if(c1.isSelected()){
                     s2=s2+""+c1.getText();
                   }
             else if(c2.isSelected()){
                     s2=s2+""+c2.getText();
                   }
          else if(c3.isSelected()){
         s2=s2+""+c3.getText();
      }
   else if(c4.isSelected()){
         s2=s2+""+c4.getText();
      }


System.out.println("You clicked on "+s2);
}
    }

}


class xyz
{
public static void main(String args[])
{
   Abc a=new Abc();
   a.setSize(1000,1000) ;
   a.setVisible(true);
   a.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}

Answer 1

我不清楚你的问题。无论如何，你将db表中的所有数据循环到最后的数据，并在while循环中设置setText。这意味着循环结束了文本框中的最后一个数据。

为什么while（rs.next（））显示文本框中的最后一个值

1 个答案: