MultiFrameImageStreamCompleter class Null safety

Manages the decoding and scheduling of image frames.

New frames will only be emitted while there are registered listeners to the stream (registered with addListener).

This class deals with 2 types of frames:

  • image frames - image frames of an animated image.
  • app frames - frames that the flutter engine is drawing to the screen to show the app GUI.

For single frame images the stream will only complete once.

For animated images, this class eagerly decodes the next image frame, and notifies the listeners that a new frame is ready on the first app frame that is scheduled after the image frame duration has passed.

Scheduling new timers only from scheduled app frames, makes sure we pause the animation when the app is not visible (as new app frames will not be scheduled).

See the following timeline example:

| Time | Event                                      | Comment                   |
|------|--------------------------------------------|---------------------------|
| t1   | App frame scheduled (image frame A posted) |                           |
| t2   | App frame scheduled                        |                           |
| t3   | App frame scheduled                        |                           |
| t4   | Image frame B decoded                      |                           |
| t5   | App frame scheduled                        | t5 - t1 < frameB_duration |
| t6   | App frame scheduled (image frame B posted) | t6 - t1 > frameB_duration |
Inheritance

Constructors

MultiFrameImageStreamCompleter({required Future<Codec> codec, required double scale, String? debugLabel, Stream<ImageChunkEvent>? chunkEvents, InformationCollector? informationCollector})
Creates a image stream completer.

Properties

debugLabel ↔ String?
A string identifying the source of the underlying image.
read / writeinherited
hashCode → int
The hash code for this object.
read-onlyinherited
hasListeners → bool
Whether any listeners are currently registered.
protected">@protectedvisibleForTesting">@visibleForTestingread-onlyinherited
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited

Methods

addListener(ImageStreamListener listener) → void
Adds a listener callback that is called whenever a new concrete ImageInfo object is available or an error is reported. If a concrete image is already available, or if an error has been already reported, this object will notify the listener synchronously.
override
addOnLastListenerRemovedCallback(VoidCallback callback) → void
Adds a callback to call when removeListener results in an empty list of listeners and there are no keepAlive handles outstanding.
inherited
debugFillProperties(DiagnosticPropertiesBuilder description) → void
Accumulates a list of strings describing the object's state. Subclasses should override this to have their information included in toString.
inherited
keepAlive() → ImageStreamCompleterHandle
Creates an ImageStreamCompleterHandle that will prevent this stream from being disposed at least until the handle is disposed.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed.
inherited
removeListener(ImageStreamListener listener) → void
Stops the specified listener from receiving image stream events.
override
removeOnLastListenerRemovedCallback(VoidCallback callback) → void
Removes a callback previously supplied to addOnLastListenerRemovedCallback.
inherited
reportError({DiagnosticsNode? context, required Object exception, StackTrace? stack, InformationCollector? informationCollector, bool silent = false}) → void
Calls all the registered error listeners to notify them of an error that occurred while resolving the image.
inherited
reportImageChunkEvent(ImageChunkEvent event) → void
Calls all the registered ImageChunkListeners (listeners with an ImageStreamListener.onChunk specified) to notify them of a new ImageChunkEvent.
protected">@protectedinherited
setImage(ImageInfo image) → void
Calls all the registered listeners to notify them of a new image.
protected">@protectedinherited
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
inherited
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) → String
A string representation of this object.
inherited
toStringShort() → String
A brief description of this object, usually just the runtimeType and the hashCode.
inherited

Operators

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