java - 显示空 View 后过滤器列表不会重新出现

Question

由于某种原因，在显示没有匹配项的空 View 后，从搜索 View 中删除所有文本后，我的 ListView 将不会重新出现。

Within my adapter class, AFAIK .clear() in mData.clear(); needs to change to something else but I don't know what to.

ItemListAdapter 类

public class ItemListAdapter extends BaseAdapter implements Filterable {

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

    public ItemListAdapter (List<Victoria> data, Context context) {
        mData = data;
        mFilteredData = new ArrayList(mData);
        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
     */
    /**
     * <p>An array filter constrains the content of the array adapter with
     * a prefix. Each item that does not start with the supplied prefix
     * is removed from the list.</p>
     */
    private class ItemFilter extends Filter {
        @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
                mFilteredData.clear();
                notifyDataSetInvalidated();
            } else {
                mFilteredData = (ArrayList<Victoria>)results.values;
                notifyDataSetChanged();
            }
        }
    }
}

过滤前

使用无效字符过滤后

清除搜索 View 并尝试再次显示列表后

Answer 1

几个小修复应该可以让一切顺利进行。首先，mData 和 mFilteredData 数据应始终是两个不同的实例。在构造函数中，将 mFilteredData 设为从 mData 复制的新实例

mFilteredData = new ArrayList(mData);

此外，在Filter中，您需要将相应的代码更新为以下内容:

if (TextUtils.isEmpty(constraint)) {
    results.count = mData.size();
    results.values = new ArrayList(mData);
}

那么您的 getView() 方法应该从 mFilteredData 而不是 mData 中提取。但理想情况下，getView() 方法应该使用 getItem(position) 方法来访问数据。这样，如果您更改数据访问位置的实现细节，则不必记住单独更新 getView() 方法。

最后，顺便说一句，您的过滤代码之所以有效，只是因为适配器不会改变 mFilteredData 或 mData。通常，必须高度同步过滤进程和适配器的其他部分，因为 performFiltering() 发生在后台线程上。如果您计划在构建后添加对修改适配器数据的支持...那么您需要开始添加同步 block 。