StreamBuilderBase<T, S> class
Null safety
Base class for widgets 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 widget building.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- StreamBuilderBase
- 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.
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-onlyinherited
-
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) → Widget -
Returns a Widget based on the
currentSummary
. -
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → State< StreamBuilderBase< T, S> > -
Creates the mutable state for this widget at a given location in the tree.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of
DiagnosticsNode
objects describing this node's children.protected">@protectedinherited -
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node.
inherited
-
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 non-existent method or property is accessed.
inherited
-
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
-
toStringDeep(
{String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String -
Returns a string representation of this node and its descendants.
inherited
-
toStringShallow(
{String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String -
Returns a one-line detailed description of the object.
inherited
-
toStringShort(
) → String -
A short, textual description of this widget.
inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
nonVirtual">@nonVirtualinherited