evict method

bool evict(Object key, { bool includeLive = true, })

Evicts a single entry from the cache, returning true if successful.

Pending images waiting for completion are removed as well, returning true if successful. When a pending image is removed the listener on it is removed as well to prevent it from adding itself to the cache if it eventually completes.

If this method removes a pending image, it will also remove the corresponding live tracking of the image, since it is no longer clear if the image will ever complete or have any listeners, and failing to remove the live reference could leave the cache in a state where all subsequent calls to putIfAbsent will return an ImageStreamCompleter that will never complete.

If this method removes a completed image, it will not remove the live reference to the image, which will only be cleared when the listener count on the completer drops to zero. To clear live image references, whether completed or not, use clearLiveImages.

The key must be equal to an object used to cache an image in ImageCache.putIfAbsent.

If the key is not immediately available, as is common, consider using ImageProvider.evict to call this method indirectly instead.

The includeLive argument determines whether images that still have listeners in the tree should be evicted as well. This parameter should be set to true in cases where the image may be corrupted and needs to be completely discarded by the cache. It should be set to false when calls to evict are trying to relieve memory pressure, since an image with a listener will not actually be evicted from memory, and subsequent attempts to load it will end up allocating more memory for the image again. The argument must not be null.

See also:

• ImageProvider, for providing images to the Image widget.

Implementation

bool evict(Object key, { bool includeLive = true }) {
  assert(includeLive != null);
  if (includeLive) {
    // Remove from live images - the cache will not be able to mark
    // it as complete, and it might be getting evicted because it
    // will never complete, e.g. it was loaded in a FakeAsync zone.
    // In such a case, we need to make sure subsequent calls to
    // putIfAbsent don't return this image that may never complete.
    final _LiveImage? image = _liveImages.remove(key);
    image?.dispose();
  }
  final _PendingImage? pendingImage = _pendingImages.remove(key);
  if (pendingImage != null) {
    if (!kReleaseMode) {
      Timeline.instantSync('ImageCache.evict', arguments: <String, dynamic>{
        'type': 'pending',
      });
    }
    pendingImage.removeListener();
    return true;
  }
  final _CachedImage? image = _cache.remove(key);
  if (image != null) {
    if (!kReleaseMode) {
      Timeline.instantSync('ImageCache.evict', arguments: <String, dynamic>{
        'type': 'keepAlive',
        'sizeInBytes': image.sizeBytes,
      });
    }
    _currentSizeBytes -= image.sizeBytes!;
    image.dispose();
    return true;
  }
  if (!kReleaseMode) {
    Timeline.instantSync('ImageCache.evict', arguments: <String, dynamic>{
      'type': 'miss',
    });
  }
  return false;
}