可分页的

Paginable is a Flutter package which makes pagination easier.

Paginable Widgets

• PaginableListView is paginable's version of ListView without default constructor.
• PaginableCustomScrollView is paginable's version of CustomScrollView
• PaginableSliverChildBuilderDelegate is paginable's version of SliverChildBuilderDelegate

Usage

Using PaginableListView

As I mentioned earlier, this widget is just a paginable's version of ListView without a default constructor. Although it does not have a default constructor, it has two named constructors, PaginableListView.builder() and PaginableListView.separated()

Using PaginableListView.builder()

This is the paginable's version of ListView.builder

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
          title: const Text('PaginableListView'),
        ),
        body: PaginableListView.builder(
            loadMore: () async {},
            errorIndicatorWidget: (exception, tryAgain) => Container(
                  color: Colors.redAccent,
                  height: 130,
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Text(
                        exception.toString(),
                        style: const TextStyle(fontSize: 16),
                      ),
                      const SizedBox(
                        height: 16.0,
                      ),
                      ElevatedButton(
                        style: ButtonStyle(
                          backgroundColor:
                              MaterialStateProperty.all(Colors.green),
                        ),
                        onPressed: tryAgain,
                        child: const Text('Try Again'),
                      ),
                    ],
                  ),
                ),
            progressIndicatorWidget: const SizedBox(
              height: 100,
              child: Center(
                child: CircularProgressIndicator(),
              ),
            ),
            itemBuilder: (context, index) => ListTile(
                  leading: CircleAvatar(
                    child: Text(
                      index.toString(),
                    ),
                  ),
                ),
            itemCount: 20),
      ),
    );
  }
}

• loadMore takes an async function which will be executed when the scroll is almost at the end.

  loadMore: () async {}
  

• errorIndicatorWidget also takes a function which contains two parameters, one being of type Exception and other being a Function(), returning a widget which will be displayed at the bottom of the scrollview when an exception occurs in the async function which we passed to the loadMore parameter. The parameter with type Exception will contain the exception which occured while executing the function passed to the parameter loadMore if exception occured and the parameter with type Function() will contain the same function which we passed to the loadMore parameter.

  errorIndicatorWidget: (exception, tryAgain) => Container(
    color: Colors.redAccent,
    height: 130,
    child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text(
          exception.toString(),
          style: const TextStyle(fontSize: 16),
        ),
        const SizedBox(
          height: 16.0,
        ),
        ElevatedButton(
          style: ButtonStyle(
            backgroundColor:
                MaterialStateProperty.all(Colors.green),
          ),
          onPressed: tryAgain,
          child: const Text('Try Again'),
        ),
      ],
    ),
  )
  

• progressIndicatorWidget takes a widget which will be displayed at the bottom of the scrollview to indicate the user that the async function we passed to the loadMore parameter is being executed.

  progressIndicatorWidget: const SizedBox(
    height: 100,
    child: Center(
      child: CircularProgressIndicator(),
    ),
  )
  

Using PaginableListView.separated()

This is the paginable's version of ListView.separated()

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
          title: const Text('PaginableListView'),
        ),
        body: PaginableListView.separated(
            separatorBuilder: (context, index) => const Divider(
                  thickness: 1.2,
                ),
            loadMore: () async {},
            errorIndicatorWidget: (exception, tryAgain) => Container(
                  color: Colors.redAccent,
                  height: 130,
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Text(
                        exception.toString(),
                        style: const TextStyle(fontSize: 16),
                      ),
                      const SizedBox(
                        height: 16.0,
                      ),
                      ElevatedButton(
                        style: ButtonStyle(
                          backgroundColor:
                              MaterialStateProperty.all(Colors.green),
                        ),
                        onPressed: tryAgain,
                        child: const Text('Try Again'),
                      ),
                    ],
                  ),
                ),
            progressIndicatorWidget: const SizedBox(
              height: 100,
              child: Center(
                child: CircularProgressIndicator(),
              ),
            ),
            itemBuilder: (context, index) => ListTile(
                  leading: CircleAvatar(
                    child: Text(
                      index.toString(),
                    ),
                  ),
                ),
            itemCount: 20),
      ),
    );
  }
}

• separatorBuilder takes a function which returns a widget and that widget only appears between list items that is why it is called separator.

  separatorBuilder: (context, index) => const Divider(thickness: 1.2)
  

Using PaginableCustomScrollView with PaginableSliverChildBuilderDelegate

Paginable also supports SliverList, but instead of using CustomScrollView one need to use PaginableCustomScrollView along with PaginableSliverChildBuilderDelegate as the delegate.

In order to use the PaginableSliverChildBuilderDelegate, one need to use one of the two methods provided by PaginableSliverChildBuilderDelegate, which are build() and separated().

Using build()

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: PaginableCustomScrollView(
          loadMore: () async {},
          slivers: [
            const SliverAppBar(
              floating: true,
              title: Text('PaginableSliverChildBuilderDelegate'),
            ),
            SliverList(
              delegate: PaginableSliverChildBuilderDelegate(
                (context, index) => ListTile(
                  leading: CircleAvatar(
                    child: Text(
                      index.toString(),
                    ),
                  ),
                ),
                errorIndicatorWidget: (exception, tryAgain) => Container(
                  color: Colors.redAccent,
                  height: 130,
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Text(
                        exception.toString(),
                        style: const TextStyle(fontSize: 16),
                      ),
                      const SizedBox(
                        height: 16.0,
                      ),
                      ElevatedButton(
                        style: ButtonStyle(
                          backgroundColor:
                              MaterialStateProperty.all(Colors.green),
                        ),
                        onPressed: tryAgain,
                        child: const Text('Try Again'),
                      ),
                    ],
                  ),
                ),
                progressIndicatorWidget: const SizedBox(
                  height: 100,
                  child: Center(
                    child: CircularProgressIndicator(),
                  ),
                ),
                childCount: 20,
              ).build(),
            ),
          ],
        ),
      ),
    );
  }
}

NOTE: While using PaginableCustomScrollView along with PaginableSliverChildBuilderDelegate, the loadMore function is situated inside the PaginableCustomScrollView, the errorIndicatorWidget and progressIndicatorWidget are situated inside the PaginableSliverChildBuilderDelegate. It is mandatory to call the build() on PaginableSliverChildBuilderDelegate because it returns a SliverChildBuilderDelegate.

Using separated()

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: PaginableCustomScrollView(
          loadMore: () async {},
          slivers: [
            const SliverAppBar(
              floating: true,
              title: Text('PaginableSliverChildBuilderDelegate'),
            ),
            SliverList(
              delegate: PaginableSliverChildBuilderDelegate(
                (context, index) => ListTile(
                  leading: CircleAvatar(
                    child: Text(
                      index.toString(),
                    ),
                  ),
                ),
                errorIndicatorWidget: (exception, tryAgain) => Container(
                  color: Colors.redAccent,
                  height: 130,
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Text(
                        exception.toString(),
                        style: const TextStyle(fontSize: 16),
                      ),
                      const SizedBox(
                        height: 16.0,
                      ),
                      ElevatedButton(
                        style: ButtonStyle(
                          backgroundColor:
                              MaterialStateProperty.all(Colors.green),
                        ),
                        onPressed: tryAgain,
                        child: const Text('Try Again'),
                      ),
                    ],
                  ),
                ),
                progressIndicatorWidget: const SizedBox(
                  height: 100,
                  child: Center(
                    child: CircularProgressIndicator(),
                  ),
                ),
                childCount: 20,
              ).separated(
                (context, index) => const Divider(
                  thickness: 1.2,
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

NOTE: The separated() method takes a function which returns a widget which is a separator.

Worth Noting

Paginable is only resposible for executing the async function passed to the loadMore parameter when the scroll is almost at the end, displaying errorIndicatorWidget at the bottom of the scrollview when an exception occurs in the loadMore and displaying progressIndicatorWidget at the bottom of the scrollview to indicate the user that the loadMore is being executed.

Paginable is not resposible for managing states, to know about different ways of managing states in Flutter, https://flutter.dev/docs/development/data-and-backend/state-mgmt/options

Contribution

If you would like to contribute to the package (e.g. by improving the documentation, fixing a bug or adding some cool new features), you are welcomed and very much appreciated to send me your pull request and if you find something wrong with the package, please feel free to open an issue.