Android Listview - 空指针异常

当我试图在 ListView 上显示项目时，显示 NullPointerException . 在这个我认为无论位置或转换视图和 TextView id和 LinearLayout id都正确 . 以下是我的代码中出现异常的行 .

viewItem.ll.setBackgroundColor(rainbow[position]);
viewItem.time.setText(timeValuesList.get(position).getElapsetime().replace(" minutes", ""));

这是MyCode：

class TimerListAdapter extends BaseAdapter{

        LayoutInflater li;
        Context ct;
        public TimerListAdapter(Context c){
            this.ct=c;
        }
        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return timeValuesList.size();
        }

        @Override
        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        @Override
        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup arg2) {
            li=(LayoutInflater)ct.getSystemService(LAYOUT_INFLATER_SERVICE);
            final ViewItem viewItem;
            if (convertView == null) {
              viewItem = new ViewItem();
              convertView=li.inflate(R.layout.salontimer_listitem, null);
              viewItem.time=(TextView)convertView.findViewById(R.id.elapse_time);
              viewItem.ll=(LinearLayout)convertView.findViewById(R.id.llayout);
              viewItem.playNpause=(ImageView)convertView.findViewById(R.id.play_pause_time);
              viewItem.addTime=(ImageView)convertView.findViewById(R.id.add_time);
              viewItem.deleteTime=(ImageView)convertView.findViewById(R.id.delete_time);
              viewItem.shareTime=(ImageView)convertView.findViewById(R.id.share_time);
            }else{
                viewItem = (ViewItem) convertView.getTag();
            }
            int[] rainbow = context.getResources().getIntArray(R.array.rainbow);
            viewItem.ll.setBackgroundColor(rainbow[position]);
            viewItem.time.setText(timeValuesList.get(position).getElapsetime().replace(" minutes", ""));
            viewItem.playNpause.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    setTime(viewItem.time,viewItem.time.getTag().toString(),Integer.parseInt(timeValuesList.get(position).getElapsetime().replace(" minutes", ""))*60*1000);
                }
            });
            viewItem.addTime.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {

                }
            });
            viewItem.deleteTime.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    sdb.DeleteSalonTime(timeValuesList.get(position).getId());
                    timeValuesList.remove(position);
                    tAdapter.notifyDataSetChanged();
                }
            });
            viewItem.shareTime.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {

                }
            });

            return convertView;
        }
        protected void setTime(final TextView tv, String tag,int time) {
             if (tv.getTag().toString().equals(tag)) {
                 CountDownTimer ct = new CountDownTimer(time, 1000) 
                  { //the timer runs for 30 seconds in this case
                     public void onTick(long millisUntilFinished){
                         int seconds = (int) ((millisUntilFinished) / 1000) % 60 ;
                         int minutes = (int) (((millisUntilFinished ) / (1000*60)) % 60); 
                         String min = Integer.toString(minutes);
                         String sec = Integer.toString(seconds);
                         tv.setText(min+":"+sec);
                     }

                    @Override
                    public void onFinish() {


                    }
                  }.start();
                }
        }

    }