Exploring Expandable List View in Flutter

In this blog post, we will dive into the world of Flutter and explore how to implement an expandable list view in a mobile application. We will walk through the code provided and understand its structure, components, and functionalities. By the end of this tutorial, you will have a solid foundation for building expandable list views in your Flutter projects.

1. Overview of the Code Structure:

Before we delve into the details, let's get an overview of the code structure. The code consists of several files, namely `main.dart`, `home_page.dart`, `list_view_class.dart`, `list_view_1.dart`, and `list_view_2.dart`. Each file serves a specific purpose and contributes to the functionality of the expandable list view.

import 'package:flutter/material.dart';

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

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

2. Setting Up the Flutter Environment:

To follow along with this tutorial, make sure you have Flutter installed on your machine. If not, we'll guide you through the installation process in this section.

3. Exploring the Main.dart File:

In this section, we'll analyze the `main.dart` file, which serves as the entry point of our Flutter application. We'll examine the `MyApp` widget and how it sets up the MaterialApp with a custom title, theme, and home page.

import 'package:flutter/material.dart';

import 'view/home_page.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

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

4. Understanding the HomePage Widget:

The `home_page.dart` file contains the `MyHomePage` widget, which serves as the main screen of our application. We'll explore how the list items are defined using the `ListItem` class and how the `ExpansionPanelList` is used to create expandable panels.

import 'package:flutter/material.dart';
import '../modal/list_view_class.dart';
import 'list_view_content/list_view_1.dart';
import 'list_view_content/list_view_2.dart';

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

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

class _MyHomePageState extends State<MyHomePage> {
  List<ListItem> listItems = [
    ListItem(
      headerValue: 'List View 1',
      expandedValue: const ListViewOne(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 2',
      expandedValue: const ListViewTwo(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 3',
      expandedValue: const ListViewOne(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 4',
      expandedValue: const ListViewTwo(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 5',
      expandedValue: const ListViewOne(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 6',
      expandedValue: const ListViewTwo(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 7',
      expandedValue: const ListViewOne(),
      isExpanded: false,
    ),
    ListItem(
      headerValue: 'List View 8',
      expandedValue: const ListViewTwo(),
      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: const Text('Expandable List View'),
      ),
      body: SingleChildScrollView(
        child: Container(
          padding: const EdgeInsets.all(16.0),
          child: ExpansionPanelList(
            elevation: 1,
            expandedHeaderPadding: const 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: item.expandedValue ?? Container(),
                isExpanded: item.isExpanded,
              );
            }).toList(),
          ),
        ),
      ),
    );
  }
}

5. Creating List Views with ListViewOne and ListViewTwo:

To demonstrate the functionality of the expandable list view, we have two sample list views defined in the `list_view_1.dart` and `list_view_2.dart` files. We'll analyze the code in these files and see how they are used within the `MyHomePage` widget.

import 'package:flutter/material.dart';

class ListViewOne extends StatelessWidget {
  const ListViewOne({super.key});

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        const Text(
          "Product Image",
          style: TextStyle(fontWeight: FontWeight.bold, fontSize: 30),
        ),
        Image.network(
            "https://fakestoreapi.com/img/71-3HjGNDUL._AC_SY879._SX._UX._SY._UY_.jpg"),
      ],
    );
  }
}

import 'package:flutter/material.dart';

class ListViewTwo extends StatelessWidget {
  const ListViewTwo({super.key});

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        const Text(
          "Product Image",
          style: TextStyle(fontWeight: FontWeight.bold, fontSize: 30),
        ),
        Image.network(
            "https://fakestoreapi.com/img/81fPKd-2AYL._AC_SL1500_.jpg")
      ],
    );
  }
}

6. Implementing the Expandable List View:

In this section, we'll dive deeper into the implementation of the expandable list view. We'll examine the `ExpansionPanelList` widget and its associated properties, such as the `expansionCallback` and `children`. We'll understand how these properties contribute to the expandable behavior of the list view.

7. Modifying List Items and Selecting List Views:

To enable the expand and collapse functionality, we need to modify the list items and keep track of the selected list view. We'll explore the `_MyHomePageState` class and understand how the `selectListView` method is used to manage the state of the list items.

8. Building and Running the App:

In this section, we'll guide you through the process of building and running the app on your device or emulator. We'll provide step-by-step instructions to ensure that you can visualize the expandable list view in action.

9. Conclusion:

Congratulations! You have successfully implemented an expandable list view in Flutter. In this tutorial, we covered the code structure, the main files involved, and the steps required to create an expandable list view. Now you have a solid foundation for building more complex list views with expandable functionality in your Flutter projects.

Conclusion:

In this blog post, we explored the code structure and functionality of an expandable list view in Flutter. We analyzed each file's purpose, examined the key components, and understood how they work together to create an interactive user interface. By following the provided code and instructions, you can now leverage the power of expandable list views to enhance the user experience in your Flutter applications.

Happy coding!

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PradeeptheDeveloper - Mobile Application Developer