StreamBuilderBase<T, S> class abstract

Base class for components that build themselves based on interaction with a specified Stream.

A StreamBuilderBase is stateful and maintains a summary of the interaction so far. The type of the summary and how it is updated with each interaction is defined by sub-classes.

Examples of summaries include:

  • the running average of a stream of integers;
  • the current direction and speed based on a stream of geolocation data;
  • a graph displaying data points from a stream.

In general, the summary is the result of a fold computation over the data items and errors received from the stream along with pseudo-events representing termination or change of stream. The initial summary is specified by sub-classes by overriding initial. The summary updates on receipt of stream data and errors are specified by overriding afterData and afterError, respectively. If needed, the summary may be updated on stream termination by overriding afterDone. Finally, the summary may be updated on change of stream by overriding afterDisconnected and afterConnected.

T is the type of stream events.

S is the type of interaction summary.

See also:

  • StreamBuilder, which is specialized for the case where only the most recent interaction is needed for component building.
Inheritance
Implementers

Constructors

StreamBuilderBase({Key? key, Stream<T>? stream})
Creates a StreamBuilderBase connected to the specified stream.
const

Properties

hashCode → int
The hash code for this object.
no setterinherited
key → Key?
Controls how one component replaces another component in the tree.
finalinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
stream → Stream<T>?
The asynchronous computation to which this builder is currently connected, possibly null. When changed, the current summary is updated using afterDisconnected, if the previous stream was not null, followed by afterConnected, if the new stream is not null.
final

Methods

afterConnected(S current) → S
Returns an updated version of the current summary reflecting that we are now connected to a stream.
afterData(S current, T data) → S
Returns an updated version of the current summary following a data event.
afterDisconnected(S current) → S
Returns an updated version of the current summary reflecting that we are no longer connected to a stream.
afterDone(S current) → S
Returns an updated version of the current summary following stream termination.
afterError(S current, Object error, StackTrace stackTrace) → S
Returns an updated version of the current summary following an error with a stack trace.
build(BuildContext context, S currentSummary) → Iterable<Component>
Returns a Component based on the currentSummary.
createElement() → Element
Creates a StatefulElement to manage this component's location in the tree.
inherited
createState() → State<StreamBuilderBase<T, S>>
Creates the mutable state for this component at a given location in the tree.
override
initial() → S
Returns the initial summary of stream interaction, typically representing the fact that no interaction has happened at all.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited

Operators

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