ViewStateListener<T, B extends BlocBase<ViewState<T>>> class

ViewStateListener is responsible for performing an action based on the ViewState.

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.

ViewStateListener is a wrapper over the BlocListener widget so it accepts a bloc object as well as a child widget and a set of handy callbacks corresponding to a given state: onLoading callback for the data loading state, onRefreshing callback for the data refreshing state, onData callback for the data success state, onEmpty callback for for no result state, onError callback function for an error state.

T - the type of items, B - the type of bloc.



ViewStateListener({Key? key, B? bloc, BlocListenerCondition<ViewState<T>>? listenWhen, LoadingCallback? onLoading, RefreshingCallback<T>? onRefreshing, @Deprecated('This callback will removed. Use "onData" instead.') SuccessCallback<T>? onSuccess, DataCallback<T>? onData, EmptyCallback? onEmpty, ErrorCallback? onError, Widget? child})


bloc → B?
The bloc whose state will be listened to. Whenever the bloc's state changes, listener will be invoked.
child Widget?
The widget which will be rendered as a descendant of the BlocListenerBase.
hashCode int
The hash code for this object.
no setterinherited
key Key?
Controls how one widget replaces another widget in the tree.
listener → BlocWidgetListener<ViewState<T>>
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.
listenWhen → BlocListenerCondition<ViewState<T>>?
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.
runtimeType Type
A representation of the runtime type of the object.
no setterinherited


createElement() → SingleChildStatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
createState() → SingleChildState<BlocListenerBase<B, ViewState<T>>>
Creates the mutable state for this widget at a given location in the tree.
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
toString({DiagnosticLevel minLevel =}) String
A string representation of this object.
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a string representation of this node and its descendants.
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a one-line detailed description of the object.
toStringShort() String
A short, textual description of this widget.


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