ScalableImageCache class

An LRU cache of ScalableImage futures derived from ScalableImageSource instances. A cache with a non-zero size could make sense, for example, as part of the state of a stateful widget that builds entries on demand, and that uses ScalableImageWidget.fromSISource to asynchronously load scalable images. See, for example, cache.dart in the example directory.

For a discussion of caching and potential reloading, see https://github.com/zathras/jovial_svg/issues/10.

If different caching semantics are desired, user code can implement ScalableImageCache; ScalableImageWidget does not use any of its private members. See also the demo_hive application to see how ScalableImageSource can be extended to load from a persistent cache.

Sample usage (see example/lib/cache.dart for the full program):

class _HomePageState extends State<HomePage> {
 ScalableImageCache _svgCache = ScalableImageCache(size: 70);
 ...
 @override
 Widget build(BuildContext context) {
   return ...
             ScalableImageWidget.fromSISource(
                 cache: _svgCache,
                 scale: 1000,
                 si: ScalableImageSource.fromSvgHttpUrl(widget.svgs[index]),
                 ...),
    ...;
  }
}

Constructors

ScalableImageCache.new({int size = 0})
Create an image cache that holds up to size image sources. A ScalableImageCache will always keep referenced ScalableImageSource instances, even if this exceeds the cache size. In this case, no unreferenced images would be kept.

Properties

hashCode → int
The hash code for this object.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
size ↔ int
The size of the cache. If the cache holds unreferenced images, the total number of images will be held to this size.
getter/setter pair

Methods

addReference(ScalableImageSource src, {ScalableImage ifAvailableSync(ScalableImage)?}) → Future<ScalableImage>
Called when a ScalableImageSource is referenced, e.g. in a stateful widget's State object's initState method. Returns a Future for the scalable image.
addReferenceV2(ScalableImageSource src) → FutureOr<ScalableImage>
Called when a ScalableImageSource is referenced, e.g. in a stateful widget's State object's initState method. Returns a Future for the scalable image.
forceReload(ScalableImageSource src) → void
If the image referenced by src is in the cache, force it to be reloaded the next time it is used.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
removeReference(ScalableImageSource src) → void
Called when a source is dereferenced, e.g. by a stateful widget's State object being disposed. Throws an exception if there had been no matching call to addReferenceV2 for this source.
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited