Flutter: Riverpod change value using methods

October 22, 2023

I’m trying to learn how to use riverpod for state management in a Flutter app. I’m building a simple counter app and I have done the following:

My provider:

@riverpod
class Counter extends _$Counter {
  int _value = 0;

  @override
  int build() => _value;

  void increment() {
    print("incrementing");
    _value++;
  }
}

In my ConsumerWidget build method I’m obtaining the following:

final counterValue = ref.watch(counterProvider);
final counter = ref.read(counterProvider.notifier);

I present the value in a Text widget in the following manner:

Text(counterValue.toString())

And my button action is the following:

onPressed: () {
    counter.increment();
}

In my console I see it’s printing "incrementing" meaning that my method is called. But the value on screen doesn’t seem to change.

What am I missing?

>Solution :

You’re changing a property of the notifier. The notifier emits only when its state is updated. If your incrementor was updating with state++, it would work, and you wouldn’t need the _value property at all.