@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View newView = convertView;
        DayHolder holder;
        Integer curr = (Integer) theList.get(position);
        if (null == convertView){
            holder = new DayHolder();
            newView = mInflater.inflate(R.layout.activity_select_day,null);
            holder.mText = (TextView) newView.findViewById(R.id.selectDays);
        }else{
            holder = (DayHolder) newView.getTag();
        }
        holder.mText.setText(curr.toString());
        return newView;
    }






1st, do not use inflate(R.layout.activity_select_day,null);. Use inflate(R.layout.activity_select_day, parent, false);. Otherwise, your layouts will not work properly when the root container of the layout file is a RelativeLayout.

2nd, if you call getTag(), you should be calling setTag(). You are not; hence, your getTag() call will always return null. Call newView.setTag(holder) in your if block, after having created your holder instance.



AFTER CORRECTION 




 @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View newView = convertView;
        DayHolder holder;
        Integer curr = (Integer) theList.get(position);
        if (null == convertView){
            holder = new DayHolder();
            newView = mInflater.inflate(R.layout.activity_select_day, parent, false);
            holder.mText = (TextView) newView.findViewById(R.id.selectDays);
            newView.setTag(holder);
        }else{
            holder = (DayHolder) newView.getTag();
        }
        holder.mText.setText(curr.toString());
        return newView;
    }