RangeError about flutter_staggered_grid_view HOT 6 CLOSED

 @override
  Widget build(BuildContext context) {
    ScreenUtil.instance = ScreenUtil.getInstance()..init(context);
    return RefreshIndicator(
      onRefresh: _refreshData,
      child: Container(
        color: Colors.grey[100],
        child: StaggeredGridView.countBuilder(
          controller: _scrollController,
          itemCount: posts.length,
          primary: false,
          crossAxisCount: 4,
          mainAxisSpacing: 4.0,
          crossAxisSpacing: 4.0,
          itemBuilder: (context, index) => TileCard(
                img: '${posts[index]['images'][0]}',
                title: '${posts[index]['title']}',
                author: '${posts[index]['userName']}',
                authorUrl: '${posts[index]['iconUrl']}',
                type: '${posts[index]['type']}',
                worksAspectRatio: posts[index]['worksAspectRatio'],
              ),
          staggeredTileBuilder: (index) => StaggeredTile.fit(2),
        ),
      ),
    );
  }

@override
  void initState() {
    super.initState();
    _getPosts(_beAdd);
    _scrollController.addListener(() {
      print('cando: ${_scrollController.position.pixels}');
      print('cando: ${_scrollController.position.maxScrollExtent}');

      if (_scrollController.position.pixels ==
          _scrollController.position.maxScrollExtent) {
            print('开始翻页了...............');
        _addMoreData();
      }
    });
  }