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

Features

  • Load data one page at a time
  • Retry failed pages
  • Override the default loading, retry, and error widgets if desired
  • ListView and GridView 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

The library provides two main 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
   }
 );

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, and retryBuilder to customize the widgets that show on loading, error, and retry respectively.

The loadingBuilder can be used as follows:

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

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.

Creating your own Pagewise Widgets:

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

Libraries

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