How to Cache Network Image in Flutter using cached_network_image package

To Cache Network Image in Flutter, you can use the cached_network_image package. This package provides a widget that can display images from the internet and cache them locally. Caching images can improve your app’s performance by reducing the need to reload images from the network repeatedly. It also provides offline access to images and reduces server load by decreasing the number of requests for the same image.

Here’s how you can implement caching for network images in Flutter:

Step 1: Add the cached_network_image package to your pubspec.yaml file

First, you need to add the cached_network_image package to your Flutter project. Open your pubspec.yaml file and add the following dependency:

dependencies:
 flutter:
    sdk: flutter
 cached_network_image: ^3.2.0

Make sure to run flutter pub get in your terminal to fetch the package.

Step 2: Import the package in your Dart file

In the Dart file where you want to use the cached network image, import the cached_network_image package:

import 'package:cached_network_image/cached_network_image.dart';

Step 3: Use the CachedNetworkImage widget

Instead of using the regular Image.network widget, use the CachedNetworkImage widget provided by the package. This widget takes the image URL as a parameter and optionally allows you to specify placeholders for loading and error states.

Here’s an example of how to use the CachedNetworkImage widget:

import 'package:flutter/material.dart';
import 'package:cached_network_image/cached_network_image.dart';

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

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Cached Network Image Example'),
        ),
        body: Center(
          child: CachedNetworkImage(
            imageUrl: "https://example.com/image.jpg",
            placeholder: (BuildContext context, url) => const CircularProgressIndicator(),
            errorWidget: (BuildContext context, url, error) => const Icon(Icons.error),
          ),
        ),
      ),
    );
 }
}

In this example, while the image is loading, a CircularProgressIndicator is displayed. If there’s an error loading the image, an error icon is shown.

Understanding Image Caching in Network Requests

The CachedNetworkImage component is designed to fetch images from online sources and store them locally. This approach significantly improves loading times for subsequent requests. While an image is being retrieved, a loading indicator can be displayed to provide visual feedback to the user. In cases where the image fails to load, an error icon can be shown instead.

Managing Loading States and Errors

The widget tree’s structure is crucial for determining where and how to display these visual elements. The loading indicator and error icon both utilize the BuildContext, which provides information about the widget’s position in the tree. This context allows for proper placement and rendering of these elements within the app’s interface. By leveraging these features, developers can create a smoother user experience when working with network images, handling both successful loads and potential errors gracefully.

When configuring the image widget, you can specify how to handle different states:

1. Loading state:  (BuildContext context, String url) => const CircularProgressIndicator() You might use a function that takes the build context and URL as parameters, returning a progress indicator while the image is being fetched.
2. Error state: (BuildContext context, String url, dynamic error) => const Icon(Icons. error) This function could return an appropriate error icon if the image fails to load.

Network Image vs Cached Network Image in Flutter

1. Network Image:

• Basic widget provided by Flutter for loading images from the internet
• Loads the image every time it’s needed
• No built-in caching mechanism
• Simpler to use for basic image loading needs

Example usage:

Image.network('https://example.com/image.jpg')

2. Cached Network Image:

• Third-party package that extends functionality of network images
• Loads image from the internet and stores it in the device’s cache
• Retrieves image from cache on subsequent loads, improving performance
• Provides more control over loading, error handling, and placeholder displays

Example usage:

CachedNetworkImage(
  imageUrl: 'https://example.com/image.jpg',
  placeholder: (context, url) => CircularProgressIndicator(),
  errorWidget: (context, url, error) => Icon(Icons.error),
)

Key differences:

1. Caching: Cached Network Image stores images locally, reducing network requests and load times for repeat views.
2. Performance: Cached Network Image typically offers better performance for frequently accessed images due to its caching mechanism.
3. Customization: Cached Network Image provides more options for handling loading states and errors.
4. Dependencies: Network Image is built into Flutter, while Cached Network Image requires adding an external package.
5. Memory management: Cached Network Image can help manage memory usage more efficiently for large or numerous images.

Choose based on your app’s needs: use Network Image for simple, one-time loads, and Cached Network Image for better performance with frequently accessed images or when you need more control over the loading process.

Conclusion

By using the cached_network_image package, you can easily cache network images in your Flutter app. This not only improves the performance of your app but also provides a better user experience by allowing images to be displayed even when the device is offline.

Remember, the key benefits of caching network images include performance improvement, offline access, reduced server load, and improved scalability and responsiveness of the server.