BlocBuilder<B extends Bloc<dynamic, S>, S> class

BlocBuilder handles building a widget in response to new states. BlocBuilder is analogous to StreamBuilder but has simplified API to reduce the amount of boilerplate code needed as well as bloc-specific performance improvements. Please refer to BlocListener if you want to "do" anything in response to state changes such as navigation, showing a dialog, etc...

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

BlocBuilder<BlocA, BlocAState>(
  builder: (context, state) {
  // return widget here based on BlocA's state
  }
)

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

BlocBuilder<BlocA, BlocAState>(
  bloc: blocA,
  builder: (context, state) {
  // return widget here based on BlocA's state
  }
)

An optional condition can be implemented for more granular control over how often BlocBuilder rebuilds. The condition function will be invoked on each bloc state change. The condition takes the previous state and current state and must return a bool which determines whether or not the builder function will be invoked. The previous state will be initialized to the state of the bloc when the BlocBuilder is initialized. condition is optional and if it isn't implemented, it will default to true.

BlocBuilder<BlocA, BlocAState>(
  condition: (previous, current) {
    // return true/false to determine whether or not
    // to rebuild the widget with state
  },
  builder: (context, state) {
    // return widget here based on BlocA's state
  }
)
Inheritance

Constructors

BlocBuilder({Key key, @required BlocWidgetBuilder<S> builder, B bloc, BlocBuilderCondition<S> condition})
BlocBuilder handles building a widget in response to new states. BlocBuilder is analogous to StreamBuilder but has simplified API to reduce the amount of boilerplate code needed as well as bloc-specific performance improvements. Please refer to BlocListener if you want to "do" anything in response to state changes such as navigation, showing a dialog, etc... [...]
const

Properties

bloc → B
The bloc that the BlocBuilderBase will interact with. If omitted, BlocBuilderBase will automatically perform a lookup using BlocProvider and the current BuildContext.
final, inherited
builder BlocWidgetBuilder<S>
The builder function which will be invoked on each widget build. The builder takes the BuildContext and current state and must return a widget. This is analogous to the builder function in StreamBuilder.
final
condition BlocBuilderCondition<S>
The BlocBuilderCondition that the BlocBuilderBase will invoke. The condition function will be invoked on each bloc state change. The condition takes the previous state and current state and must return a bool which determines whether or not the builder function will be invoked. The previous state will be initialized to state when the BlocBuilderBase is initialized. condition is optional and if it isn't implemented, it will default to true.
final, inherited
hashCode int
The hash code for this object. [...]
@nonVirtual, read-only, inherited
key Key
Controls how one widget replaces another widget in the tree. [...]
final, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

build(BuildContext context, S state) Widget
Returns a widget based on the BuildContext and current state.
override
createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
inherited
createState() State<BlocBuilderBase<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. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
inherited
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
Returns 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, inherited