How to generate stream in flutter - flutter

Question

I am making some experiment with flutter stream. I have a class for generating stream of int. Here is the class :
class CounterRepository {
int _counter = 123;
void increment() {
_counter++;
}
void decrement() {
_counter--;
}
Stream<int> watchCounter() async* {
yield _counter;
}
}
I expect with the change of _counter, watchCounter() will yield updated counter value. When I call increment() or decrement() from UI, it seems the value of _counter is changing but watchCounter doesn't yield the updated _counter value. How to yield updated _counter value here? I am using StreamBuilder from UI to get the streamed data.

Answer 1

You have created your streams using -
Stream<int> watchCounter() async* {
yield _counter;
}
But to reflect the changes of your stream, you need to receive those stream events. You can control those stream events using a StreamController
Creating a stream
Future<void> main() async {
var stream = watchCounter();
}
Using that stream
stream.listen
Subscribes to the stream by calling the listen function and supplys it
with a Function to call back to when there's a new value available.
stream.listen((value) {
print('Value from controller: $value');
});
There are many other approaches to control and manage streams but for your particular question .listen will do the job.

Answer 2

You are missing an infinite while loop, it's a manual stream.
Stream<dynamic> watchCounter() async* {
while (true) {
// you can change it to 5 seconds or higher
await Future.delayed(const Duration(seconds: 1));
yield _counter;
}
}
And after that you just need to call listen:
watchCounter().listen((value) {
// hear can be empty if you want.
});
You can put it in your init state to run, don't put it in your widget build, please.
This should work fine