flutter移植DragAbleGridView官方demo长按图标实现拖拽、删除功能，移植到工程里面代码后报错！

Question

代码如下：

static commonFuctionsEdit(BuildContext context) {

DragAbleGridViewState dragAbleGridViewState = new DragAbleGridViewState();
List<ItemBin> itemBins = new List(); 
var editSwitchController=  EditSwitchController();

final List<String> icons1 = [
  'assets/images/gongsi_kaoqinguanli3.png',
  'assets/images/gongsi_xinchouguanli3.png',
  'assets/images/gongsi_zhaopinguanli3.png',
  'assets/images/gongsi_renshidangan3.png',
  'assets/images/gongsi_videomeeting.png',
  'assets/images/gongsi_wanxingxuetang3.png',
  'assets/images/gongsi_yunyingbaogao3.png'
];

icons1.forEach((value) {
  itemBins.add(new ItemBin(value));
  //print(value);
});

dragAbleGridViewState.initState();
if(null != editSwitchController){
  editSwitchController.editStateChanged();

}


    return Scaffold(
       body: editSwitchController != null ? DragAbleGridView(
        mainAxisSpacing:10.0,
        crossAxisSpacing:10.0,
        childAspectRatio:1.0,
        crossAxisCount: 4,
        itemBins: itemBins,
        editSwitchController:editSwitchController,
        isOpenDragAble: true,   //长按实现拖动的功能
        animationDuration: 300, //milliseconds
        longPressDuration: 800, //milliseconds
        deleteIcon: Image.asset("assets/images/close.png",width: 15.0 ,height: 15.0 ),
        //通过调用delete监听器实现对items的删除
        deleteIconClickListener: (index) {},
        child: (int position){
          return Container(
            child: Image.asset(
                itemBins[position].data,
                width: 50.0,
                height: 50.0,
            ),
          );
        },
        // child: ,
      ):Container(),
  );

}

我也判空了啊，

大佬们有遇到过的嘛，头疼ing