GroupListView In Flutter

GroupListView In Flutter :

This flutter tutorial post is GroupListView In Flutter. GroupListView is use select programming language, history, select team etc. That program is group by name, date wise.

if (sort && elements.isNotEmpty)
      if (groupBy(elements[0]) is Comparable) {
        elements.sort((e1, e2) =><
            (groupBy(e1) as Comparable).compareTo(groupBy(e2) as Comparable));
      } else {
        elements
            .sort((e1, e2) => ('${groupBy(e1)}').compareTo('${groupBy(e2)}'));
      }
    }

Screenshot :

main.dart

import 'package:flutter/material.dart';

import 'grouped_list.dart';

void main() => runApp(MyApp());

List _elements = [
  {'name': 'Basic Java', 'group': 'Java'},
  {'name': 'PHP', 'group': 'Java'},
  {'name': 'BLoC Pattern', 'group': 'Flutter'},
  {'name': 'Lifecycle Android', 'group': 'Android'},
  {'name': 'Basic Flutter', 'group': 'Flutter'},
  {'name': 'Inheritance', 'group': 'Java'},
];

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Tutorial',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text('Grouped List View In Flutter'),
        ),
        body: GroupedListView<dynamic, String>(
          groupBy: (element) => element['group'],
          elements: _elements,
          sort: true,
          groupSeparatorBuilder: (String value) => Padding(
            padding: const EdgeInsets.all(8.0),
            child: Center(
                child: Text(
                  value,
                  style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
                )),
          ),
          itemBuilder: (c, element) {
            return Card(
              elevation: 0.5,
              margin: new EdgeInsets.symmetric(horizontal: 10.0, vertical: 6.0),
              child: Container(
                child: ListTile(
                  contentPadding:
                  EdgeInsets.symmetric(horizontal: 20.0, vertical: 10.0),
                  leading: Icon(Icons.account_circle),
                  title: Text(element['name']),
                  trailing: Icon(Icons.arrow_forward),
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}

grouped_list.dart

library grouped_list;

import 'package:flutter/material.dart';

class GroupedListView<T, E> extends ListView {
  GroupedListView({
    @required E Function(T element) groupBy,
    @required Widget Function(E value) groupSeparatorBuilder,
    @required Widget Function(BuildContext context, T element) itemBuilder,
    bool sort = true,
    Widget separator = const Divider(height: 0.0),
    List<T> elements,
    Key key,
    Axis scrollDirection = Axis.vertical,
    ScrollController controller,
    bool primary,
    ScrollPhysics physics,
    bool shrinkWrap = false,
    EdgeInsetsGeometry padding,
    bool addAutomaticKeepAlives = true,
    bool addRepaintBoundaries = true,
    bool addSemanticIndexes = true,
    double cacheExtent,
  }) : super.builder(
          key: key,
          scrollDirection: scrollDirection,
          controller: controller,
          primary: primary,
          physics: physics,
          shrinkWrap: shrinkWrap,
          padding: padding,
          itemCount: elements.length * 2,
          addAutomaticKeepAlives: addAutomaticKeepAlives,
          addRepaintBoundaries: addRepaintBoundaries,
          addSemanticIndexes: addSemanticIndexes,
          cacheExtent: cacheExtent,
          itemBuilder: (context, index) {
            int actualIndex = index ~/ 2;
            if (index.isEven) {
              E curr = groupBy(elements[actualIndex]);
              E prev = actualIndex - 1 < 0
                  ? null
                  : groupBy(elements[actualIndex - 1]);

              if (prev != curr) {
                return groupSeparatorBuilder(curr);
              }
              return separator;
            }
            return itemBuilder(context, elements[actualIndex]);
          },
        ) {
    if (sort && elements.isNotEmpty) {
      if (groupBy(elements[0]) is Comparable) {
        elements.sort((e1, e2) =>
            (groupBy(e1) as Comparable).compareTo(groupBy(e2) as Comparable));
      } else {
        elements
            .sort((e1, e2) => ('${groupBy(e1)}').compareTo('${groupBy(e2)}'));
      }
    }
  }
}

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