Loading a flutter app efficiently on slow internet connections
Flutter App Efficient Loading in Slow Internet Connection: Strategies and Code Examples
In today’s world, people use mobile apps on the go, often with limited internet connectivity. As a Flutter developer, it’s essential to ensure that your app loads quickly and smoothly, even on slow internet connections. Here are some strategies and code examples to optimize your app’s loading performance.
Optimize Your Assets
To optimize your app’s assets, use compressed images and videos that are optimized for the web. You can use tools like ImageOptim to reduce file sizes without compromising quality. Here’s an example of how to use ImageOptim in your Flutter app:
import 'package:image/image.dart' as img;
Future<List<int>> optimizeImage(String imagePath) async {
final bytes = await rootBundle.load(imagePath);
final image = img.decodeImage(bytes.buffer.asUint8List());
final optimizedImage = img.encodePng(img.copyResize(image, width: 800));
return optimizedImage.toList();
}In this example, we’re using the image package to decode and resize the image and then encode it as a PNG. The resulting byte array can be used in your app.
Use Lazy Loading
Lazy loading loads only the content that is necessary for the initial view of the app. For example, if you have a long list of images, load only the images that are visible on the screen initially, and load more as the user scrolls down. Here’s an example of how to implement lazy loading in your Flutter app:
class LazyLoadingList extends StatefulWidget {
@override
_LazyLoadingListState createState() => _LazyLoadingListState();
}
class _LazyLoadingListState extends State<LazyLoadingList> {
final _scrollController = ScrollController();
final _itemsPerPage = 10;
var _loadedItems = 0;
var _items = <String>[];
@override
void initState() {
_scrollController.addListener(_scrollListener);
super.initState();
}
@override
void dispose() {
_scrollController.dispose();
super.dispose();
}
void _scrollListener() {
if (_scrollController.offset >=
_scrollController.position.maxScrollExtent &&
!_scrollController.position.outOfRange) {
_loadMoreItems();
}
}
Future<void> _loadMoreItems() async {
await Future.delayed(Duration(seconds: 1)); // simulate network latency
setState(() {
_items.addAll(_generateItems(_loadedItems, _itemsPerPage));
_loadedItems += _itemsPerPage;
});
}
List<String> _generateItems(int start, int count) {
return List.generate(count, (index) => 'Item ${start + index + 1}');
}
@override
Widget build(BuildContext context) {
return ListView.builder(
controller: _scrollController,
itemCount: _items.length + 1,
itemBuilder: (context, index) {
if (index == _items.length) {
return Center(child: CircularProgressIndicator());
} else {
return ListTile(title: Text(_items[index]));
}
},
);
}
}In this example, we’re using a ListView.builder to build a list of items. We use a ScrollController to detect when the user has reached the end of the list and then load more items. The CircularProgressIndicator is displayed while new items are being loaded.
Use Placeholders
Placeholders or skeleton screens can give the user an idea of what the content will look like before it loads. This can help keep the user engaged while the content loads.
Here’s an example of how to implement placeholders in your Flutter app:
class PlaceholderList extends StatelessWidget {
final int itemCount;
const PlaceholderList({Key? key, required this.itemCount}) : super(key: key);
@override
Widget build(BuildContext context) {
return ListView.builder(
itemCount: itemCount,
itemBuilder: (context, index) {
return Card(
child: ListTile(
leading: Skeleton(),
title: Skeleton(width: 100),
subtitle: Skeleton(width: 80),
),
);
},
);
}
}
class Skeleton extends StatelessWidget {
final double width;
final double height;
const Skeleton({Key? key, this.width = 50, this.height = 50})
: super(key: key);
@override
Widget build(BuildContext context) {
return Container(
width: width,
height: height,
decoration: BoxDecoration(
color: Colors.grey[300],
borderRadius: BorderRadius.circular(8),
),
);
}
}In this example, we’re using a ListView.builder to build a list of cards, each with a Skeleton widget to represent the content that is loading. The Skeleton widget is simply a container with a gray background and rounded corners.
Reduce the Number of HTTP Requests
To reduce the number of HTTP requests your app makes, you can combine multiple files into one or use a content delivery network (CDN). Here’s an example of how to use a CDN to load images in your Flutter app:
class ImageFromCDN extends StatelessWidget {
final String imagePath;
const ImageFromCDN({Key? key, required this.imagePath}) : super(key: key);
@override
Widget build(BuildContext context) {
final cdnUrl = 'https://cdn.example.com/';
final imageUrl = cdnUrl + imagePath;
return Image.network(imageUrl);
}
}In this example, we’re using a CDN to load the image from a different domain than our app’s domain. This can improve loading performance by reducing the number of requests to our app’s server.
Cache Data
To avoid downloading data that has already been downloaded, you can use a cache to store data. Here’s an example of how to use a cache in your Flutter app:
class CachedData extends StatelessWidget {
final String url;
const CachedData({Key? key, required this.url}) : super(key: key);
@override
Widget build(BuildContext context) {
return FutureBuilder(
future: _getData(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return Text(snapshot.data);
} else if (snapshot.hasError) {
return Text(‘Error: ${snapshot.error}’);
} else {
return CircularProgressIndicator();
}
},
);
}
Future<String> _getData() async {
final cache = await CacheManager.getInstance();
final data = await cache.get(url);
if (data != null) {
return utf8.decode(data.buffer.asUint8List());
} else {
final response = await http.get(Uri.parse(url));
if (response.statusCode == 200) {
await cache.put(url, response.bodyBytes);
return response.body;
} else {
throw Exception(‘Failed to load data’);
}
}
}
}
class CacheManager {
static CacheManager? _instance;
static Future<CacheManager> getInstance() async {
if (_instance == null) {
_instance = CacheManager._();
}
return _instance!;
}
In this example, we’re using a CacheManager class to store data in memory. When the CachedData widget is built, it checks if the data is in the cache. If it is, it returns the data. If it isn’t, it downloads the data and stores it in the cache for future use.
Conclusion
In this article, we’ve explored various techniques to make your Flutter app load efficiently in slow internet connections. We’ve discussed using lazy loading, optimizing images, using placeholders, reducing HTTP requests, and caching data. By implementing these techniques, you can improve your app’s loading performance, provide a better user experience, and increase user engagement.
Remember, it’s important to test your app’s performance on different internet speeds and devices to ensure that it performs well in all scenarios. Happy coding!
