筛选列表不会因空结果而改变

Question

每当过滤我的列表视图后没有结果，我希望它消失，文本视图出现在屏幕的中心。我知道这一切都需要进入if (results.count == 0) {}但我得到一些与布局相关的错误，我不知道如何解决。 '？'应该表示列表视图片段的布局，但由于代码不在布局类中，我还没有得到什么需要替换它的线索（同样适用于{{1}在(this)）。所有相关的帮助将不胜感激。

我想要实现的目标如下：

TextView tv = new TextView(this);

ItemListAdapter类

if (results.count == 0) {

1. Make the list invisible
2. Create a text view programmatically and show it

}

FilterListFragment类

public class ItemListAdapter extends BaseAdapter implements Filterable {

    private List<Victoria> mData;
    private List<Victoria> mFilteredData;
    private LayoutInflater mInflater;
    private ItemFilter mFilter;
    private ListView mListView;

    public ItemListAdapter (List<Victoria> data, Context context) {
        mData = data;
        mFilteredData = data;
        mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

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

    @Override
    public String getItem(int position) {
        return mFilteredData.get(position).getItem();
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder;
        if (convertView == null) {
           convertView = mInflater.inflate(R.layout.item_row, parent, false);
            holder = new ViewHolder();

            holder.title = (TextView) convertView.findViewById(R.id.item_title);
            holder.description = (TextView) convertView.findViewById(R.id.item_description);

            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.title.setText(mFilteredData.get(position).getItem());
        holder.description.setText(mFilteredData.get(position).getItemDescription());

        return convertView;
    }

    @Override
    public Filter getFilter() {
        if (mFilter == null) {
            mFilter = new ItemFilter();
        }
        return mFilter;
    }

    /**
     * View holder
     */
    static class ViewHolder {
        private TextView title;
        private TextView description;
    }

    /**
     * Filter for filtering list items
     */
    private class ItemFilter extends Filter {

        /**
         * Invoked on a background thread.  This is where all the filter logic should go
         * @param constraint the constraint to filter on
         * @return the resulting list after applying the constraint
         */
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            FilterResults results = new FilterResults();

            if (TextUtils.isEmpty(constraint)) {
                results.count = mData.size();
                results.values = mData;
            } else {
                //Create a new list to filter on
                List<Victoria> resultList = new ArrayList<Victoria>();
                for (Victoria str : mData) {
                    if (str.getItemDescription().toLowerCase().contains(constraint.toString().toLowerCase())) {
                        resultList.add(str);
                    }
                }
                results.count = resultList.size();
                results.values = resultList;
            }
            return results;
        }

        /**
         * Runs on ui thread
         * @param constraint the constraint used for the result
         * @param results the results to display
         */
        @SuppressWarnings("unchecked")
        @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
    if (results.count == 0) {
        //Make list invisible
        //Make text view visible
        notifyDataSetInvalidated();
    } else {
        mFilteredData = (ArrayList<Victoria>)results.values;
        notifyDataSetChanged();
    }
}
    }
}

Answer 1

你不必处理它，Android会为你做。在TextView中添加代表空视图的fragment_filter_string_list.xml，其ID为android:id="@android:id/empty"。 Android将负责显示/隐藏它，具体取决于getCount()的值。

修改，

要实现您的目标，您的publishResults应该看起来像

mFilteredData = (ArrayList<Victoria>)results.values;
notifyDataSetChanged();

您也可能希望保留mFilteredData的副本，以便在查询更改或重置时还原数据集