flutter_pagewise 1.2.1

  • README.md
  • CHANGELOG.md
  • Example
  • Installing
  • Versions
  • 96

A library for widgets that load their content one page (or batch) at a time (also known as lazy-loading and pagination).

flutter_pagewise

Features #

  • Load data one page at a time
  • Retry failed pages
  • Override the default loading, retry, and error widgets if desired
  • Manage loading of data more closely using a PagewiseLoadController
  • ListView and GridView implementations
  • SliverList and SliverGrid implementations
  • Extendability using inheritance

Breaking Change Starting V1.0.0: #

The library has been rewritten in version 1.0.0 to provide a more efficient implementation that does not require a totalCount parameter and shows only one loading sign when users scroll down. In addition, a new parameter has been added to itemBuilder callback to provide the index if needed by the user.

Installing the library: #

Like any other package, add the library to your pubspec.yaml dependencies:

dependencies:
    flutter_pagewise:

Then import it wherever you want to use it:

import 'package:flutter_pagewise/flutter_pagewise.dart';

Using the library #

Check out the example

The library provides the following widgets:

  • PagewiseGridView: A pagewise implementation of GridView. It could be used as follows:
PagewiseGridView.count(
  pageSize: 10,
  crossAxisCount: 2,
  mainAxisSpacing: 8.0,
  crossAxisSpacing: 8.0,
  childAspectRatio: 0.555,
  padding: EdgeInsets.all(15.0),
  itemBuilder: (context, entry, index) {
    // return a widget that displays the entry's data
  },
  pageFuture: (pageIndex) {
    // return a Future that resolves to a list containing the page's data
  },
);
  • PagewiseListView: A pagewise implementation of ListView. It could be used as follows:
PagewiseListView(
  pageSize: 10,
  padding: EdgeInsets.all(15.0),
  itemBuilder: (context, entry, index) {
    // return a widget that displays the entry's data
  },
  pageFuture: (pageIndex) {
    // return a Future that resolves to a list containing the page's data
  }
);
  • PagewiseSliverGrid: A pagewise implementation of SliverGrid. It could be used similar to PagewiseGridView for cases where a sliver is needed.
  • PagewiseSliverList: A pagewise implementation of SliverList. It could be used similar to PagewiseListView for cases where a sliver is needed.

The classes provide all the properties of ListViews and GridViews. In addition, you must provide the itemBuilder, which tells Pagewise how you want to render each element, and pageFuture, which Pagewise calls to fetch new pages. Please note that pageFuture must not return more values than mentioned in the pageSize parameter.

Customizing the widget: #

In addition to the required parameters, Pagewise provides you with optional parameters to customize the widget. You have loadingBuilder, errorBuilder, noItemsFoundBuilder, and retryBuilder to customize the widgets that show on loading, error, no found items and retry respectively.

The loadingBuilder can be used as follows:

loadingBuilder: (context) {
  return Text('Loading...');
}

The noItemsFoundBuilder can be used as follows:

noItemsFoundBuilder: (context) {
  return Text('No Items Found');
}

The retryBuilder can be used as follows:

retryBuilder: (context, callback) {
  return RaisedButton(
    child: Text('Retry'),
    onPressed: () => callback()
  );
}

Thus, the retryBuilder provides you with a callback that you can call when you want to retry.

The errorBuilder is only relevant when showRetry is set to false, because, otherwise, the retryBuilder is shown instead. The errorBuilder can be used as follows:

errorBuilder: (context, error) {
  return Text('Error: $error');
}

Check the classes' documentation for more details.

Providing your own PagewiseLoadController: #

Pagewise widgets manage the loading of pages using a PagewiseLoadController. This controller is responsible for fetching data, handling errors, etc.

You don't have to provide a controller yourself when creating a Pagewise widget. The widget will create one for you. However you might wish to create one yourself in order to achieve some effects.

Notice though that if you provide a controller yourself, you should provide the [pageFuture] and [pageSize] parameters to the controller instead of the widget.

A possible use case of the controller is to force a reset of the loaded pages using a RefreshIndicator. you could achieve that as follows (note that we added the Future.value({}) as a dummy return value, because onRefresh expects a Future, but reset does not return one):

final _pageLoadController = PagewiseLoadController(
  pageSize: 6,
  pageFuture: BackendService.getPage
);

@override
Widget build(BuildContext context) {
  return RefreshIndicator(
    onRefresh: () async {
      this._pageLoadController.reset();
      await Future.value({});
    },
    child: PagewiseListView(
        itemBuilder: this._itemBuilder,
        pageLoadController: this._pageLoadController,
    ),
  );
}

Another use case for creating the controller yourself is if you want to listen to the state of Pagewise and act accordingly. For example, you might want to show a snackbar when we reach the end of the list In that case, you could do:

final _pageLoadController = PagewiseLoadController(
  pageSize: 6,
  pageFuture: BackendService.getPage
);

@override
void initState() {
  super.initState();
  this._pageLoadController.addListener(() {
    if (!this._pageLoadController.hasMoreItems) {
      Scaffold.of(context).showSnackBar(
        SnackBar(
          content: Text('No More Items!')
        )
      );
    }
  });
}

Creating your own Pagewise Widgets: #

You need to inherit from the Pagewise class. Check the code of PagewiseListView and PagewiseGridView for examples

1.2.1 - 06/02/2019 #

  • Fixes the GridView exception in case the number of items in the last page is less than page size (issues #35, #33)
  • Fixes the race condition that might cause the same page to be fetched multiple times (Issues #6, #30)
  • Improves types, generic types, and default values on parameters (Issues #24, #25, #32)
  • Implements fixes and improvements to the README and the example

1.2.0 - 19/12/2018 #

  • Add scenario of moving from one widget.controller to another in didUpdateWidget
  • Implement noItemsFoundBuilder

1.1.1 - 18/12/2018 #

  • Add didUpdateWidget to PagewiseState class for cases of switching controller

1.1.0 - 18/12/2018 #

  • Implement controller pattern for more control and visibility over page loading
  • Provide support for slivers (PagewiseSliverList and PagewiseSliverGrid)

1.0.0 - 16/12/2018 #

  • Re-architect the library for more efficiency and ease of use.

0.5.0 - 22/08/2018 #

  • Provide ability to retry
  • Fix case of page futures refiring when rebuilt

0.4.1 - 17/08/2018 #

  • Decrease size of GIF in README to make it load faster

0.4.0 - 11/08/2018 #

  • Make future final in _FutureBuilderWrapper
  • Remove unneeded _pages data structure and operations
  • Provide ItemListBuilder for cases where we want to build a list of widgets for each data entry
  • Provide controller property to allow custom ScrollController

0.3.0 - 04/08/2018. #

0.2.0 - 31/07/2018. #

  • Replace loadingWidget with a loadingBuilder that accepts a BuildContext and returns a widget.
  • Fix environment constraints in pubspec.yaml
  • Make the example better looking, and the demo as well
  • Mention lazy-loading in the README.
  • Reformat the code using flutter format

0.1.2 - 29/07/2018. #

  • Add gif to README.

0.1.1 - 29/07/2018. #

  • Small fix to README.

0.1.0 - 29/07/2018. #

  • Provided basic functionality for Pagewise class, PagewiseGridView class and PagewiseListView class.

example/README.md

The example in lib/main.dart:

uses Pagewise to display paginated data in 4 different ways:

  1. ListView
  2. GridView
  3. SliverListView
  4. SliverGridView

All the views fetch their data from JSON placeholder, an online service that provides dummy JSON data for testing. The ListViews fetch the posts from the service, while the GridViews fetch the images.

The service allows us to specify a start and limit parameters, which allows us to effectively achieve pagination. The start parameter specifies the first element to fetch, while the limit specifies the number of elements to fetch, that is, the page size.

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:


dependencies:
  flutter_pagewise: ^1.2.1

2. Install it

You can install packages from the command line:

with Flutter:


$ flutter pub get

Alternatively, your editor might support flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:


import 'package:flutter_pagewise/flutter_pagewise.dart';
  
Version Uploaded Documentation Archive
1.2.3 Mar 28, 2019 Go to the documentation of flutter_pagewise 1.2.3 Download flutter_pagewise 1.2.3 archive
1.2.2 Feb 6, 2019 Go to the documentation of flutter_pagewise 1.2.2 Download flutter_pagewise 1.2.2 archive
1.2.1 Feb 6, 2019 Go to the documentation of flutter_pagewise 1.2.1 Download flutter_pagewise 1.2.1 archive
1.2.0 Dec 18, 2018 Go to the documentation of flutter_pagewise 1.2.0 Download flutter_pagewise 1.2.0 archive
1.1.1 Dec 18, 2018 Go to the documentation of flutter_pagewise 1.1.1 Download flutter_pagewise 1.1.1 archive
1.1.0 Dec 18, 2018 Go to the documentation of flutter_pagewise 1.1.0 Download flutter_pagewise 1.1.0 archive
1.0.0 Dec 16, 2018 Go to the documentation of flutter_pagewise 1.0.0 Download flutter_pagewise 1.0.0 archive
0.5.0 Aug 22, 2018 Go to the documentation of flutter_pagewise 0.5.0 Download flutter_pagewise 0.5.0 archive
0.4.1 Aug 17, 2018 Go to the documentation of flutter_pagewise 0.4.1 Download flutter_pagewise 0.4.1 archive
0.4.0 Aug 11, 2018 Go to the documentation of flutter_pagewise 0.4.0 Download flutter_pagewise 0.4.0 archive

All 15 versions...

Popularity:
Describes how popular the package is relative to other packages. [more]
92
Health:
Code health derived from static analysis. [more]
99
Maintenance:
Reflects how tidy and up-to-date the package is. [more]
100
Overall:
Weighted score of the above. [more]
96
Learn more about scoring.

We analyzed this package on May 8, 2019, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.3.0
  • pana: 0.12.15
  • Flutter: 1.5.8

Platforms

Detected platforms: Flutter

References Flutter, and has no conflicting libraries.

Health suggestions

Fix lib/flutter_pagewise.dart. (-1 points)

Analysis of lib/flutter_pagewise.dart reported 2 hints:

line 7 col 9: The class 'Future' was not exported from 'dart:core' until version 2.1, but this code is required to be able to run on earlier versions.

line 460 col 3: The class 'Future' was not exported from 'dart:core' until version 2.1, but this code is required to be able to run on earlier versions.

Dependencies

Package Constraint Resolved Available
Direct dependencies
Dart SDK >=1.19.0 <3.0.0
async ^2.0.7 2.2.0
flutter 0.0.0
Transitive dependencies
collection 1.14.11
meta 1.1.6 1.1.7
sky_engine 0.0.99
typed_data 1.1.6
vector_math 2.0.8
Dev dependencies
flutter_test