关于 JButton监听出错

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at delbookinf$2.actionPerformed(delbookinf.java:147)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
    at java.awt.Component.processMouseEvent(Component.java:6041)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
    at java.awt.Component.processEvent(Component.java:5806)
    at java.awt.Container.processEvent(Container.java:2058)
    at java.awt.Component.dispatchEventImpl(Component.java:4413)
    at java.awt.Container.dispatchEventImpl(Container.java:2116)
    at java.awt.Component.dispatchEvent(Component.java:4243)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
    at java.awt.Container.dispatchEventImpl(Container.java:2102)
    at java.awt.Window.dispatchEventImpl(Window.java:2440)
    at java.awt.Component.dispatchEvent(Component.java:4243)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)我在按钮加监听后出现这个错误一直没能解决，大家帮一下吧sure.addActionListener(new ActionListener(){
  public void actionPerformed(ActionEvent e){
  Connection conn=null;
  Statement state=null;
  ResultSet rs=null;
  if(bid.getText().equals(""))
  { JOptionPane.showMessageDialog(null,"请输入图书编号");
   }
      else      
     try{    
         String url = "jdbc:odbc:driver={Microsoft Access Driver (*.mdb)};DBQ=libary.mdb";
               Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                conn = DriverManager.getConnection(url, "", "");
           state = conn.createStatement();
               String sql = "select * from booktable where 图书编号='"+bidt.getText().trim()+"'";
               rs=state.executeQuery(sql);
            while(rs.next()){
               bkit.setText(rs.getString("图书类别"));
               bpbt.setText(rs.getString("出版社"));
               bptt.setText(rs.getString("出版时间"));
               isbnt.setText(rs.getString("ISBN"));
               bwrt.setText(rs.getString("作者"));
               bprt.setText(rs.getString("图书价格"));
               bnat.setText(rs.getString("图书名称"));
               
            }
                } catch (ClassNotFoundException ee) {
ee.printStackTrace();
} catch (SQLException ee) {
ee.printStackTrace();
} finally {
try {
if(rs != null) {
rs.close();
rs = null;
}
if(state != null) {
state.close();
state = null;
}
if(conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e1) {
e1.printStackTrace();
}
}
  } } );
 
  delbook.addActionListener(new ActionListener(){
  public void actionPerformed(ActionEvent e){
  Connection conn=null;
  Statement state=null;
  ResultSet rs=null;
   
     try{    
         String url = "jdbc:odbc:driver={Microsoft Access Driver (*.mdb)};DBQ=libary.mdb";
               Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                conn = DriverManager.getConnection(url, "", "");
           state = conn.createStatement();
               String sql = "delete  from booktable where 图书编号='"+bidt.getText().trim()+"'";
                state.executeUpdate(sql);
               
                } catch (ClassNotFoundException ee) {
ee.printStackTrace();
} catch (SQLException ee) {
ee.printStackTrace();
} finally {
try {
 
rs.close();
rs = null;
 
 
state.close();
state = null;
 
 
conn.close();
conn = null;
 
} catch (SQLException e1) {
e1.printStackTrace();
}
}
         bkit.setText("");
               bpbt.setText("");
               bptt.setText("");
               isbnt.setText("");
               bwrt.setText("");
               bprt.setText("");
               bnat.setText("");

  } } );