Listen to Changes from a Notifier

[PeterAkande]

Just as Its easy to add a listener callback to the BlocConsumer in flutter bloc, It would be great is there is such callback In the Consumers and Selectors provided by Provider.

For example, a Consumer with a Listener can be defined as:

Consumer<SomeState>(
    listener: (state){},
    builder: (context, state, child){
        return SomeWidget();
     },
);

[rrousselGit]

This had been requested before.
I haven't found a graceful way to do it quite yet.

Bloc does it because it has Bloc.listen. But there's no equivalent for providers.
The closest is State.didChangeDependencies, but it can be invoked for reasons other than a specific dependency change.

[PeterAkande]

Did this as a work around that.

What do you think about it?

class ConsumerWithListener<T> extends StatefulWidget {
  final Widget? child;
  final void Function(T value) listener;
  final Widget Function(
    BuildContext context,
    T value,
    Widget? child,
  ) builder;

  const ConsumerWithListener({
    super.key,
    this.child,
    required this.listener,
    required this.builder,
  });

  @override
  State<ConsumerWithListener<T>> createState() =>
      _ConsumerWithListenerState<T>();
}

class _ConsumerWithListenerState<T> extends State<ConsumerWithListener<T>> {
  Timer? debounceTimer;

  @override
  Widget build(BuildContext context) {
    return Consumer<T>(
      builder: (context, T value, child) {
        if (debounceTimer?.isActive ?? false) debounceTimer?.cancel();

        /// The build Function can be called multiple Times for each notification
        /// But we don't want our listener to be called so many times
        /// So lets Debounce some unneeded calls.
        /// This is especially needed in cases where A Navigator.push is done in the
        /// Listen function.
        ///
        /// An error that is due to assert(!_debugLock) is thrown.
        debounceTimer = Timer(const Duration(milliseconds: 100), () {
          widget.listener.call(value);
        });

        return widget.builder.call(context, value, child);
      },
      child: widget.child,
    );
  }
}

[souravbapari1]

i think this feature is helpful, OK i Add This