LocalOrCachedNetworkImageProvider class

An ImageProvider for loading image from local file or network using a cache.

Some tips of parameters:

  1. At lease one of file and url (or fileFuture and urlFuture, or file and url results of these two futures) must be non-null value, otherwise argument error will be thrown.

  2. If given file (or result of fileFuture) is not null and exists, this provider will try to load image from this file, this also means local image has a higher priority than network image.

  3. If given file is not null but does not exist, behavior will be depended by fileMustExist. Exception Image file "xxx" is not found. will be thrown if fileMustExist is true, otherwise url will be used as fallback.

  4. If given file is null or url is decided to be used, while given url (or result of urlFuture) is not null, this provider will try to load image from this web url, invalid format exception or network error exception may be thrown here.

  5. If given file is null or not exists, while url is null (not include invalid format exceptions), this provider will throw an exception Image file "xxx" is not found while given url is null.

  6. Only file (or fileFuture), url (or urlFuture), scale, maxWidth, maxHeight will be used to determine whether it represents the same image.

Inheritance

Constructors

LocalOrCachedNetworkImageProvider({Key? key, required File? file, required String? url, double? scale = 1.0, bool fileMustExist = true, Map<String, String>? headers, BaseCacheManager? cacheManager, String? cacheKey, int? maxWidth, int? maxHeight, bool asyncHeadFirst = false, Duration? networkTimeout, void onFileLoading()?, void onUrlLoading()?, void onFileLoaded(Object? err)?, void onUrlLoaded(Object? err)?})
Creates LocalOrCachedNetworkImageProvider with nullable file and url.
const
LocalOrCachedNetworkImageProvider.fromFutures({Key? key, required Future<File?>? fileFuture, required Future<String?>? urlFuture, double? scale = 1.0, bool fileMustExist = true, Map<String, String>? headers, BaseCacheManager? cacheManager, String? cacheKey, int? maxWidth, int? maxHeight, bool asyncHeadFirst = false, Duration? networkTimeout, void onFileLoading()?, void onUrlLoading()?, void onFileLoaded(Object? err)?, void onUrlLoaded(Object? err)?})
Creates LocalOrCachedNetworkImageProvider with nullable fileFuture and urlFuture.
const
LocalOrCachedNetworkImageProvider.fromLocal({Key? key, required File file, double? scale = 1.0, bool fileMustExist = true, void onFileLoading()?, void onFileLoaded(Object? err)?})
Creates LocalOrCachedNetworkImageProvider with non-null file only.
const
LocalOrCachedNetworkImageProvider.fromLocalWithFuture({Key? key, required Future<File?> fileFuture, double? scale = 1.0, bool fileMustExist = true, void onFileLoading()?, void onFileLoaded(Object? err)?})
Creates LocalOrCachedNetworkImageProvider with non-null fileFuture only.
const
LocalOrCachedNetworkImageProvider.fromNetwork({Key? key, required String url, double? scale = 1.0, Map<String, String>? headers, BaseCacheManager? cacheManager, String? cacheKey, int? maxWidth, int? maxHeight, bool asyncHeadFirst = false, Duration? networkTimeout, void onUrlLoading()?, void onUrlLoaded(Object? err)?})
Creates LocalOrCachedNetworkImageProvider with non-null url only.
const
LocalOrCachedNetworkImageProvider.fromNetworkWithFuture({Key? key, required Future<String?> urlFuture, double? scale = 1.0, Map<String, String>? headers, BaseCacheManager? cacheManager, String? cacheKey, int? maxWidth, int? maxHeight, bool asyncHeadFirst = false, Duration? networkTimeout, void onUrlLoading()?, void onUrlLoaded(Object? err)?})
Creates LocalOrCachedNetworkImageProvider with non-null urlFuture only.
const

Properties

asyncHeadFirst → bool
The flag to check whether need to send HEAD request asynchronously to get network image's real size, defaults to false.
final
cacheKey → String?
The cache key for network image and will be stored in cacheManager, defaults to url or urlFuture itself.
final
cacheManager → BaseCacheManager?
The cache manager which is used to check whether network image has already been loaded.
final
file → File?
The local file of the image to load.
final
fileFuture → Future<File?>?
The local file future of the image to load.
final
fileMustExist → bool
The flag to decide whether to throw exception or use url as fallback, when given file does not exist, defaults to true.
final
hashCode → int
The hash code for this object.
no setteroverride
headers → Map<String, String>?
The headers for requesting network image, such as "Authorization" and "Referer".
final
key → Key?
The key that can be used to reload the image in force when different Key passed.
final
maxHeight → int?
If this value is not null and ImageCacheManager is used, the image will be resized on disk to fit the height. This value will be ignored if a normal cacheManager is used.
final
maxWidth → int?
If this value is not null and ImageCacheManager is used, the image will be resized on disk to fit the width. This value will be ignored if a normal cacheManager is used.
final
networkTimeout → Duration?
The timeout duration for network image loading, defaults to null, which means not to check.
final
onFileLoaded → (void Function(Object? err)?)
The callback function to be called when the local image finished loading. Here null err represents it succeeded, otherwise represents it failed.
final
onFileLoading → (void Function()?)
The callback function to be called when the local image starts to load.
final
onUrlLoaded → (void Function(Object? err)?)
The callback function to be called when the network image finished loading. Here null err represents it succeeded, otherwise represents it failed.
final
onUrlLoading → (void Function()?)
The callback function to be called when the network image starts to load.
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
scale → double?
The scale of the image, defaults to 1.0.
final
url → String?
The web url of the image to load.
final
urlFuture → Future<String?>?
The web url future of the image to load.
final

Methods

createStream(ImageConfiguration configuration) → ImageStream
Called by resolve to create the ImageStream it returns.
inherited
evict({ImageCache? cache, ImageConfiguration configuration = ImageConfiguration.empty}) → Future<bool>
Evicts an entry from the image cache.
inherited
load(LocalOrCachedNetworkImageProvider key, dynamic decode) → ImageStreamCompleter
loadBuffer(LocalOrCachedNetworkImageProvider key, DecoderBufferCallback decode) → ImageStreamCompleter
Converts a key into an ImageStreamCompleter, and begins fetching the image.
inherited
loadImage(LocalOrCachedNetworkImageProvider key, ImageDecoderCallback decode) → ImageStreamCompleter
Converts a key into an ImageStreamCompleter, and begins fetching the image.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
obtainCacheStatus({required ImageConfiguration configuration, ImageErrorListener? handleError}) → Future<ImageCacheStatus?>
Returns the cache location for the key that this ImageProvider creates.
inherited
obtainKey(ImageConfiguration configuration) → Future<LocalOrCachedNetworkImageProvider>
Converts an ImageProvider's settings plus an ImageConfiguration to a key that describes the precise image to load.
override
resolve(ImageConfiguration configuration) → ImageStream
Resolves this image provider using the given configuration, returning an ImageStream.
inherited
resolveStreamForKey(ImageConfiguration configuration, ImageStream stream, LocalOrCachedNetworkImageProvider key, ImageErrorListener handleError) → void
Called by resolve with the key returned by obtainKey.
inherited
toString() → String
A string representation of this object.
override

Operators

operator ==(dynamic other) → bool
The equality operator.
override