A utility similar to Compose’s remember, which leverages anlifecycle to let Flutter’s BuildContext remember an instance and provide corresponding management functions.

Usage

1.1 Prepare the lifecycle environment.


class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    // Use LifecycleApp to wrap the default App
    return LifecycleApp(
      child: MaterialApp(
        title: 'Remember Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        navigatorObservers: [
          //Use LifecycleNavigatorObserver.hookMode() to register routing event changes
          LifecycleNavigatorObserver.hookMode(),
        ],
        home: const HomeRememberDemo(title: 'Remember Home Page'),
      ),
    );
  }
}

The current usage of PageView and TabBarViewPageView should be replaced with LifecyclePageView and LifecycleTabBarView. Alternatively, you can wrap the items with LifecyclePageViewItem. You can refer to anlifecycle for guidance.

1.2 Use remember to let the context retain an object.

class HomeRememberDemo extends StatelessWidget {
  final String title;

  const HomeRememberDemo({super.key, required this.title});

  @override
  Widget build(BuildContext context) {
    // 记住一个 ValueNotifier<int> listen:并且自动刷新当前context
    final counter = context.rememberValueNotifier(value: 0, listen: true);
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: Text(
          'You have pushed the button this many times: ${counter.value}',
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          counter.value++;
        },
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}

Description

  /// Remembers the object with the current [context], and will return
  /// the same object in the future.
  /// * The call order, [T], and [key] determine whether it is the same
  ///   object. If any of them change, a new object will be created.
  /// * [factory] and [factory2] define how to construct this object.
  ///   They cannot both be null. [factory] has higher priority than [factory2].
  /// * [onCreate] defines the handling logic after the object is created.
  /// * [onDispose] defines how to handle cleanup when the object is disposed.
  ///   It runs after [context]'s [dispose]. **Important: Do NOT use
  ///   [context]-related content here.**
  T remember<T extends Object>(
      {T Function()? factory,
      T Function(Lifecycle)? factory2,
      void Function(Lifecycle, T)? onCreate,
      FutureOr<void> Function(T)? onDispose,
      Object? key})
      
  /// Quickly creates a reusable [TabController].
  /// * The call order, [key], [initialIndex], [animationDuration],
  ///   and [length] determine whether it is considered the same object.
  ///   If any of these change, a new object will be created.
  TabController rememberTabController({
    int initialIndex = 0,
    Duration? animationDuration,
    required int length,
    void Function(Lifecycle, TabController)? onCreate,
    FutureOr<void> Function(TabController)? onDispose,
    Object? key,
  })
  
  /// Quickly creates a reusable [AnimationController].
  /// * The call order, [key], [value], [duration], [reverseDuration],
  ///   [debugLabel], [lowerBound], [upperBound], and [animationBehavior]
  ///   determine whether it is considered the same object.
  ///   If any of these change, a new object will be created.
  AnimationController rememberAnimationController({
    double? value,
    Duration? duration,
    Duration? reverseDuration,
    String? debugLabel,
    double lowerBound = 0.0,
    double upperBound = 1.0,
    AnimationBehavior animationBehavior = AnimationBehavior.normal,
    void Function(Lifecycle, AnimationController)? onCreate,
    FutureOr<void> Function(AnimationController)? onDispose,
    Object? key,
  })
  
  /// Quickly creates a reusable [ScrollController].
  /// * The call order, [key], [initialScrollOffset], [keepScrollOffset],
  ///   and [debugLabel] determine whether it is considered the same object.
  ///   If any of these change, a new object will be created.
  ScrollController rememberScrollController({
    double initialScrollOffset = 0.0,
    bool keepScrollOffset = true,
    String? debugLabel,
    void Function(Lifecycle, ScrollController)? onCreate,
    FutureOr<void> Function(ScrollController)? onDispose,
    Object? key,
  })
  
  /// Quickly creates a reusable [ValueNotifier].
  /// * The call order, [T], and [key] determine whether it is considered
  ///   the same object. If any of these change, a new object will be created.
  /// * [value], [factory], and [factory2] define how to initialize the
  ///   [ValueNotifier]. At least one must be non-null. These are not used
  ///   as keys for updates.
  /// * [listen] enables the current [context] to automatically listen to
  ///   the created [ValueNotifier]. This is only effective on the first
  ///   creation; subsequent changes have no effect.
  ValueNotifier<T> rememberValueNotifier<T>({
    T? value,
    T Function()? factory,
    T Function(Lifecycle)? factory2,
    void Function(Lifecycle, ValueNotifier<T>)? onCreate,
    FutureOr<void> Function(ValueNotifier<T>)? onDispose,
    bool listen = false,
    Object? key,
  })

Additional information

See anlifecycle

See cancelable

See an_lifecycle_cancellable

See an_viewmodel

Libraries

remember