ListenableFutureBuilder<T extends Listenable> class

A widget that awaits initialization and then rebuilds when the it receives a notification from the Listenable. Use this widget with ChangeNotifier ValueNotifier, or other Listenable controllers to rebuild the widget when the value changes.

Given a AsyncListenableBuilder<T> and a builder which builds widgets from the state of the Listenable, this class will automatically register itself as a listener of the Listenable and call the builder with updated values when the value changes.

Performance optimizations

If your builder function contains a subtree that does not depend on the value of the Listenable, it's more efficient to build that subtree once instead of rebuilding it on every animation tick.

If you pass the pre-built subtree as the child parameter, the ListenableFutureBuilder will pass it back to your builder function so that you can incorporate it into your build.

Using this pre-built child is entirely optional, but can improve performance significantly in some cases and is therefore a good practice.

{@tool snippet}

This sample demonstrates how you could use a ListenableFutureBuilder to wait for the initialization to complete, show a CircularProgressIndicator while waiting, and trigger rebuild on state changes without the need for setState

import 'package:flutter/material.dart';
import 'package:listenable_future_builder/listenable_future_builder.dart';

void main() {
  runApp(
    MaterialApp(
      theme: ThemeData(
        useMaterial3: true,
        primarySwatch: Colors.blue,
      ),
      home: ListenableFutureBuilder<ValueNotifier<int>>(
        listenable: getController,
        builder: (context, child, snapshot) => Scaffold(
          appBar: AppBar(),
          body: Center(
              child: snapshot.connectionState == ConnectionState.done
                  ? Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        const Text(
                          'You have pushed the button this many times:',
                        ),
                        Text(
                          '${snapshot.data!.value}',
                          style: Theme.of(context).textTheme.headlineMedium,
                        ),
                      ],
                    )
                  : const CircularProgressIndicator.adaptive()),
          floatingActionButton: FloatingActionButton(
            onPressed: () => snapshot.data?.value++,
            tooltip: 'Increment',
            child: const Icon(Icons.add),
          ),
        ),
      ),
      debugShowCheckedModeBanner: false,
    ),
  );
}

Future<ValueNotifier<int>> getController() async =>
    Future.delayed(const Duration(seconds: 2), () => ValueNotifier<int>(0));

{@end-tool}

Constructors

ListenableFutureBuilder({required Future<T> listenable(), required AsyncListenableBuilder<T> builder, Widget? child, Future<void> disposeListenable(T listenable)?, Key? key}): Creates a ListenableFutureBuilder.
const

Properties

builder → AsyncListenableBuilder<T>: A AsyncListenableBuilder which builds a widget depending on the Listenable such as a ChangeNotifier
final
child → Widget?: A predefined widget which is passed back to the builder.
final
disposeListenable → (Future<void> Function(T listenable)?): Provides an opportunity to dispose of the Listenable when the _ListenableFutureBuilderState is disposed.
final
hashCode → int: The hash code for this object.
no setterinherited
key → Key?: Controls how one widget replaces another widget in the tree.
finalinherited
listenable → Future<T> Function(): Instantiates the Future whose return value you depend on in order to build. This should perform initialization logic for the Listenable and return it
final
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

createElement() → StatefulElement: Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() → State<ListenableFutureBuilder<T>>: 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.
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