import 'package:flutter_image_add_drag_sort/flutter_image_add_drag_sort.dart';

  List<ImageDataItem> imageList = [];

  ...

  ImageAddDragContainer(
      key: _key,  // GlobalKey()
      data: imageList,
      maxCount: 9,
      readOnly: false,
      draggableMode: false,
      itemSize: Size(imgSize, imgSize),
      addWidget: Icon(Icons.add, size: 24, color: Colors.black38),
      onAddImage: (onBegin) async {
        // add image 
        return await doAddImage(onBegin);
      },
      onChanged: (items) async {
        imageList = items;
      },
      onTapItem: (item, index) {
        Scaffold.of(context).showSnackBar(SnackBar(content: Text("click item: $index, ${item.key}")));
      },
      builderItem: (context, key, url, type) {
        // custom builder item
        return Container(
          color: Colors.yellow,
          child: url == null || url.isEmpty ? null : Image.file(File(url)),
        );
      },
  )