disposable_cached_images

A flutter package for downloading, caching, displaying and releasing images from memory.

Features

Display images from the Internet and/or local files (assets and device storage).

Caching images in the cache directory.

Cancel the download if the image widget has been disposed to reduce bandwidth usage.

Remove the image from memory if the image widget has been disposed to reduce device memory usage.

High performance due to the use of dart:isolate and Web-Workers on web

Usage

Setting up

All you have to do is Initializing the cache and wrap the root widget with DisposableImages.

void main() {
  await DisposableImages.init();

  runApp(const DisposableImages(MyApp()));
}

additional steps for web only

Download web_js from the example directory and copy it into your web folder, and then include it in index.html

<!doctype html>
<html lang="en">
<head>
  <script src="flutter.js" defer></script>
  <script src="web_js/worker_helper.js" defer></script>
</head>
<body></body>
</html>

Now your app is ready to use the package.

initialization options

enableWebCache

enable / disable web image caching

maximumDecodedImagesCount

The maximum number of decoded images that should be kept in memory when using DisposableImages.decodedImages

maximumDecode

The maximum number of images to be decoded simultaneously

maximumDownload

The maximum number of images to be downloaded simultaneously

Displaying images

Use DisposableCachedImage named constructors to display images.

Obtaining an image from a URL

DisposableCachedImage.network(imageUrl: 'https://picsum.photos/id/23/200/300');

Obtaining a local image from assets using path

DisposableCachedImage.asset(imagePath: 'assets/images/a_dot_burr.jpeg');

Obtaining a local image from device storage using path

DisposableCachedImage.local(imagePath: 'assets/images/a_dot_burr.jpeg');

Display dynamic height images

If you are using dynamic height images, you should declare this as shown below to avoid UI jumping

DisposableCachedImage.network(
  imageUrl: imageUrl,
  isDynamicHeight: true,
  width: MediaQuery.of(context).size.width * 0.3,
),

width required when displaying dynamic height images

You can display your custom widgets while the image is loading, downloading, has an error and when it is ready as shown below

DisposableCachedImage.network(
  imageUrl: 'https://picsum.photos/id/23/200/300',
  onLoading: (context) => const Center(
    child: Icon(Icons.downloading),
  ),
  progressBuilder: (context, progress) => Center(
    child: LinearProgressIndicator(value: progress),
  ),
  onError: (context, error, stackTrace, retryCall) => Center(
    child: IconButton(
      onPressed: retryCall,
      icon: const Icon(Icons.download),
    ),
  ),
  onImage: (context, imageWidget, height, width) => Stack(
    children: [
      imageWidget,
      MyWidget(),
    ],
  ),
);

Resize images

You can change the image size to the provided width and \ or height by enabling resizeImage (disabled by default) to reduce raster thread usage when using high resolution images, if this option is enabled the same provider instance would be used for the number of images that share the same url \ path with a different image size for each widget to have a gallery like experience.

To change the size of the images in bytes before they are saved to the storage, provide maxCacheWidth and \ or maxCacheHeight.

DisposableCachedImage.network(
 imageUrl: imageUrl,
 maxCacheWidth: 300,
 width: 200,
 resizeImage: true,
),

Clipping

You can clip the image either with rounded corners by providing BorderRadius

DisposableCachedImage.network(
  imageUrl: imageUrl,
  borderRadius: const BorderRadius.all(Radius.circular(20)),
),

Or by setting BoxShape to get oval image

DisposableCachedImage.network(
  imageUrl: imageUrl,
  shape: BoxShape.circle,
),

Keeping images alive

By default each image is removed from memory when it is not being used by any widget, however you can keep some images in memory for the entire application lifecycle as shown below

DisposableCachedImage.network(
  imageUrl: imageUrl,
  keepAlive: true,
),

The other arguments are similar if not quite the same as Image Widget

Decode images before displaying

You can use DisposableImages.decodedImages to decode images before displaying them in case you need to show images immediately without loading

  // decode network images
  DisposableImages.decodedImages.addNetwork(url);

  // decode loacl images
  DisposableImages.decodedImages.addLocal(path);

  // decode assets images
  DisposableImages.decodedImages.addAssets(path);

If you decode the images in this way, you will have to dispose the images manually or set the maximum number of decoded images

// set the maximum number of decoded images, old images will be removed if this number is exeeded
// this is optional and can be null
DisposableImages.init(maximumDecodedImagesCount: 100);


// dispose an image by key
// the key is path if the image is local or assets, if it's a network image the key is the url
DisposableImages.decodedImages.dispose(key);

// dispose all images
DisposableImages.decodedImages.disposeAll();

Remove all cached images from the device storage

DisposableCachedImage.clearCache();

Web Note :

the package is only usable for CanvasKit renderer for now, if you try to use it with HTML renderer, images won't load as mentioned in #2

How it works

The package uses RawImage with dart-ui-Image directly without the need for ImageProvider

Stores and retrieves files using indexedDB on web and dart:io on other platforms.

Disposing and changing image state using flutter_riverpod with state_notifier.

Downloading images with Fetch API on web and dart:_http on other platforms.

Example app

The example directory has a sample application that uses this plugin.

Live web demo.

Roadmap

Fixing web html render issue

Improve package documentation

Further improvements