flutter_pagewise loads all images at once instead of lazyloading - flutter

Question

I'm using Flutter with the package flutter_pagewise to add lazyloading to a large image grid which loads images from local assets.
I created json file which includes all paths for the images. With this file I want to work as future source in flutter_pagewise.
The function which returns the list from json for pagewise
Future<List> getDemoImagesJson(int offset, int limit) async {
String demoImages = await DefaultAssetBundle.of(context)
.loadString("assets/demo/demo.json");
final jsonResult = json.decode(demoImages);
List images = [];
for (var i in jsonResult) {
images.add({"id": 1, "title": "sample", "thumbnailUrl": i});
}
final list = List.from(images).toList();
var listWithOffset = list.skip(offset).toList();
final finalList = listWithOffset.getRange(0, limit).toList();
return ImageModel.fromJsonList(finalList);
}
The ImageModel class (copied from official documentation)
class ImageModel {
String title;
String id;
String thumbnailUrl;
ImageModel.fromJson(obj) {
this.title = obj['title'];
this.id = obj['id'].toString();
this.thumbnailUrl = obj['thumbnailUrl'];
}
static List<ImageModel> fromJsonList(jsonList) {
return jsonList.map<ImageModel>((obj) => ImageModel.fromJson(obj)).toList();
}
}
The PageWise Widget
PagewiseGridView.count(
shrinkWrap: true,
physics: ClampingScrollPhysics(),
pageSize: 10,
crossAxisCount: 3,
mainAxisSpacing: 8.0,
crossAxisSpacing: 8.0,
padding: EdgeInsets.all(15.0),
itemBuilder: (context, entry, index) {
return Container(
child: Image.asset(entry.thumbnailUrl,
fit: BoxFit.cover));
},
pageFuture: (pageIndex) {
return getDemoImagesJson(pageIndex * 10, 10);
})
What I expect: I expect that the Widget loads only 10 images and after I scroll down to the end of the page it loads other 10 images...until all images did load.
What I get: The Widget loads all images at once (as batch). There is no lazyload effect after reaching the bottom of the page.
Where is the issue?