侦听器对象中的Nullpointer异常

Question

try{
     db.doSendFeedback(casetoken, responsetoken, physicianemail,ratval, new sendFeedbackListener());

}catch(Exception e){
     System.out.println("excep"+e);
}

我在这里NullPointerException sendFeedbackListener()

public class sendFeedbackListener implements ServerResponseListener {
     public void ServerResponseReceived(int code, String Msg) 
     {
          alert(code, Msg);
     }
}