queryData.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               List<Student> students = DataSupport.findAll(Student.class);
               for(Student student:students){
                   Log.d("MainActivity", "name = " + student.getName());
                   Log.d("MainActivity", "score = " + student.getScore());
                   Log.d("MainActivity", "class_id = " + student.getClass_id());
               }
           }
       });