BlocListener<B extends StateStreamable<S>, S> class

Takes a BlocWidgetListener and an optional bloc and invokes the listener in response to state changes in the bloc. It should be used for functionality that needs to occur only in response to a state change such as navigation, showing a SnackBar, showing a Dialog, etc... The listener is guaranteed to only be called once for each state change unlike the builder in BlocBuilder.

If the bloc parameter is omitted, BlocListener will automatically perform a lookup using BlocProvider and the current BuildContext.

BlocListener<BlocA, BlocAState>(
  listener: (context, state) {
    // do stuff here based on BlocA's state
  },
  child: Container(),
)

Only specify the bloc if you wish to provide a bloc that is otherwise not accessible via BlocProvider and the current BuildContext.

BlocListener<BlocA, BlocAState>(
  value: blocA,
  listener: (context, state) {
    // do stuff here based on BlocA's state
  },
  child: Container(),
)

An optional listenWhen can be implemented for more granular control over when listener is called. listenWhen will be invoked on each bloc state change. listenWhen takes the previous state and current state and must return a bool which determines whether or not the listener function will be invoked. The previous state will be initialized to the state of the bloc when the BlocListener is initialized. listenWhen is optional and if omitted, it will default to true.

BlocListener<BlocA, BlocAState>(
  listenWhen: (previous, current) {
    // return true/false to determine whether or not
    // to invoke listener with state
  },
  listener: (context, state) {
    // do stuff here based on BlocA's state
  },
  child: Container(),
)
Inheritance
Implemented types

Constructors

BlocListener({required BlocWidgetListener<S> listener, Key? key, B? bloc, BlocListenerCondition<S>? listenWhen, Widget? child})
Takes a BlocWidgetListener and an optional bloc and invokes the listener in response to state changes in the bloc. It should be used for functionality that needs to occur only in response to a state change such as navigation, showing a SnackBar, showing a Dialog, etc... The listener is guaranteed to only be called once for each state change unlike the builder in BlocBuilder.
const

Properties

bloc → B?
The bloc whose state will be listened to. Whenever the bloc's state changes, listener will be invoked.
finalinherited
child → Widget?
The widget which will be rendered as a descendant of the BlocListenerBase.
finalinherited
hashCode → int
The hash code for this object.
no setterinherited
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
listener → BlocWidgetListener<S>
The BlocWidgetListener which will be called on every state change. This listener should be used for any code which needs to execute in response to a state change.
finalinherited
listenWhen → BlocListenerCondition<S>?
An optional listenWhen can be implemented for more granular control over when listener is called. listenWhen will be invoked on each bloc state change. listenWhen takes the previous state and current state and must return a bool which determines whether or not the listener function will be invoked. The previous state will be initialized to the state of the bloc when the BlocListener is initialized. listenWhen is optional and if omitted, it will default to true.
finalinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

createElement() → SingleChildStatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() → SingleChildState<BlocListenerBase<B, S>>
Creates the mutable state for this widget at a given location in the tree.
inherited
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent 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.
inherited