java - 如何获取android ListView 中某一列的总和？

Question

我正在尝试获取 SQL 表中的数字总数，我首先在 android 和 sql 之间连接，但我不能将表格列中的数字相加并显示在 TextView 中，就像我想得到总数然后一列中的数字在 TextView 中显示它们，有人可以帮我完成这个任务吗？

这是我使用的代码 ListView

public class MyAppAdapter extends BaseAdapter         //has a class viewholder which holds
    {
        public class ViewHolder
        {
            TextView textDate;
            TextView textTotal;
            TextView textLastTotal;
            TextView textCount;
            TextView textTaxs;

        }

        public List<ClassListItems2> parkingList;

        public Context context;
        ArrayList<ClassListItems2> arraylist;

        private MyAppAdapter(List<ClassListItems2> apps, Context context)
        {
            this.parkingList = apps;
            this.context = context;
            arraylist = new ArrayList<ClassListItems2>();
            arraylist.addAll(parkingList);
        }

        @Override
        public int getCount() {
            return parkingList.size();
        }

        @Override
        public Object getItem(int position) {
            return position;
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) // inflating the layout and initializing widgets
        {

            View rowView = convertView;
            ViewHolder viewHolder= null;
            if (rowView == null)
            {
                LayoutInflater inflater = getLayoutInflater();
                rowView = inflater.inflate(R.layout.listcontent2, parent, false);
                viewHolder = new ViewHolder();
                viewHolder.textDate = (TextView) rowView.findViewById(R.id.date);
                viewHolder.textLastTotal = (TextView) rowView.findViewById(R.id.lasttotal);
                viewHolder.textTaxs = (TextView) rowView.findViewById(R.id.date3);
                viewHolder.textCount = (TextView) rowView.findViewById(R.id.InvoicescCount);
                viewHolder.textTotal = (TextView) rowView.findViewById(R.id.total);
                rowView.setTag(viewHolder);
            }
            else
            {
                viewHolder = (ViewHolder) convertView.getTag();
            }
            // here setting up names and images
            viewHolder.textDate.setText(parkingList.get(position).getDate()+"");
            viewHolder.textTotal.setText(parkingList.get(position).getTotal());
            viewHolder.textLastTotal.setText(parkingList.get(position).getLasttotal());
            viewHolder.textTaxs.setText(parkingList.get(position).getTaxs());
            viewHolder.textCount.setText(parkingList.get(position).getInvoicecount());





            listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    //What happens when you click on a place!



                }
            });

            return rowView;
        }

Answer 1

此适配器在其构造函数中包含一个集合(列表)。

要了解总数，请在处理该集合的 Activity/Fragment 中使用:

parkingList.size()

获取总和:

float total;

for (ClassListItems2 actualItem : parkingList) {
   total += actualItem.getTotal()
}

所有这些逻辑都必须在 Activity/Fragment 中执行，而不能在 Adapter 中执行，因为 Adapter 仅具有表示/视觉逻辑。