Creating an Expandable List View in Flutter

In mobile app development, it is common to have lists that can expand and collapse to show additional information. Flutter provides a powerful widget called `ExpansionPanelList` that allows us to create expandable lists easily. In this tutorial, we will explore how to implement an expandable list view in Flutter using the `ExpansionPanelList` widget.

Setting Up the Project

Before we dive into the implementation details, make sure you have Flutter installed and set up on your machine. Create a new Flutter project and replace the contents of the `main.dart` file with the code provided in this tutorial.

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Expandable List View',
      theme: ThemeData(
        primarySwatch: Colors.orange,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

  @override
  // ignore: library_private_types_in_public_api
  _MyHomePageState createState() => _MyHomePageState();
}

class ListItem {
  String headerValue;
  String expandedValue;
  bool isExpanded;

  ListItem({
    required this.headerValue,
    required this.expandedValue,
    required this.isExpanded,
  });
}

class _MyHomePageState extends State<MyHomePage> {
  List<ListItem> listItems = [
    ListItem(
      headerValue: 'List View 1',
      expandedValue: 'This is List View 1',
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 2',
      expandedValue: 'This is List View 2',
      isExpanded: false,
    ),
    // Add more list items for additional list views
  ];

  void selectListView(int index) {
    setState(() {
      for (var i = 0; i < listItems.length; i++) {
        listItems[i].isExpanded = (i == index);
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Expandable List View'),
      ),
      body: SingleChildScrollView(
        child: Container(
          padding: EdgeInsets.all(16.0),
          child: ExpansionPanelList(
            elevation: 1,
            expandedHeaderPadding: EdgeInsets.all(0),
            expansionCallback: (int index, bool isExpanded) {
              selectListView(index);
            },
            children: listItems.map<ExpansionPanel>((ListItem item) {
              return ExpansionPanel(
                headerBuilder: (BuildContext context, bool isExpanded) {
                  return ListTile(
                    title: Text(item.headerValue),
                  );
                },
                body: ListTile(
                  title: Text(item.expandedValue),
                ),
                isExpanded: item.isExpanded,
              );
            }).toList(),
          ),
        ),
      ),
    );
  }
}

Implementing the Expandable List View

The code provided sets up a basic Flutter application with an expandable list view. Let's go through the important parts of the code:

1.  `ListItem` Class: We define a custom class `ListItem` to represent each item in the expandable list view. Each item has a header value, an expanded value, and a boolean flag to determine if it is expanded or not.
2.  `_MyHomePageState` Class: This is the stateful widget that builds the main home page of our application. It manages the list of `ListItem` objects and handles the expansion and collapse of the list items based on user interaction.
3.  `selectListView` Method: This method is called when a list tile is tapped. It updates the `isExpanded` property of the selected list item and rebuilds the widget to reflect the changes.
4. `build` Method: In the `build` method, we define the structure of our app's UI. The `ExpansionPanelList` widget is used to display the expandable list view. We map each `ListItem` to an `ExpansionPanel` widget, which consists of a header and a body. The header displays the title of the list item, and the body shows the expanded value. The `expansionCallback` is set to the `selectListView` method to handle the expansion and collapse of list items.

In this tutorial, we learned how to create an expandable list view in Flutter using the `ExpansionPanelList` widget. We explored the implementation of a basic expandable list view that allows users to expand and collapse list items to view additional information. You can further enhance this implementation by customizing the UI, adding more list items, or integrating additional functionality.

By utilizing the powerful features of Flutter, you can create dynamic and interactive user interfaces that provide a seamless user experience.

Happy coding!