flutter_pagination_helper 1.0.1+2

Reduce your boilerplate code to implement pagination in flutter project. User ListHelper widget and pass call back method to listen scroll event using your custom ItemListCallback.

Flutter Pagination Helper

Flutter pagination helper is used to reduce boilerplate code for pagination.

Description

Here we have optimised concept of Model from model-view-intent pattern as described by hannes dorfmann. So as a short note you can use this dependency for pagination by providing the state of model retrieved from your business logic. This state could be from progress bar visibility, data, error or data loading completion. Here to show paginated list you need to pass only list of widget as a data.

Implementation

To add flutter pagination helper dependency add following dependency in pubspec.yaml

dependencies:
  flutter_pagination_helper: ^1.0.1+2

Common usage

• To use this dependency you have to assign PaginatedListWidget to the child of parent widget. In the code the prototype is mentioned to setup a paginated list. It can be retrived from list_helper.dart file.
• In parameter you can optionally assign progressWidget if you need to design your custom widget as progress. You can change color for default progress by assigning colorSwatch parameter to your parent material app theme.
• As 2nd parameter you have to assign itemListCallback which will be called each time user reach to end of listview. It can be retrived from item_list_callback.dart file.

import 'package:flutter_pagination_helper/pagination_helper/event_model.dart';
import 'package:flutter_pagination_helper/pagination_helper/item_list_callback.dart';
import 'package:flutter_pagination_helper/pagination_helper/list_helper.dart';

class CustomProgressWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: PaginatedListWidget(
            progressWidget: Center(
              child: Text("Loading..."),
            ),
            itemListCallback: OnScrollCallback()),
      ),
    );
  }
}

• In itemListCallback you have to implement your custom Callback as mentioned in code. It will return Future of generic type EventModel.

class OnScrollCallback<T extends Widget> extends ItemListCallback {
  @override
  Future<EventModel<T>> getItemList() {
    // TODO: implement getItemList
    return null;
  }
}

• EventModel is ui model to distinguish state as mentioned in code. It will be retrieved from event_model.dart file.
  • Here progress indicates the visibility of progress bar while loading item.
  • data will be list of widgets which will be displayed in list view. [Note : This field will contain items which are not retrieved on previous call].
  • error is a error message when api fails and it will be displayed as SnackBar.
  • stopLoading will be true when all items are retrieved and we need to stop pagination.

class EventModel<T extends Widget> {
  final bool progress;
  final List<T> data;
  final String error;
  final bool stopLoading;

  EventModel({this.progress, this.data, this.error, this.stopLoading});
}

• Get the clear understanding for flutter pagination from this article.
• You can refer following demo for different perspactive.
  • Pagination with default progress widget.
  • Pagination with custom progress widget.
  • Pagination with error message.
  • Pagination implemented with hacker rank api integration.

• Flutter pagination helper
• Lab: Write your first Flutter app
• Cookbook: Useful Flutter samples

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