Which is efficient? Flutter StreamBuilder Widget vs Stream.Listen() with setState()

Question

I am writing a periodic stream with duration of 1 second to show time:

stream: Stream.periodic(Duration(seconds: 1)),
builder: (context, snapshot) {
  return Text(DateTime.now().toString());
}

Also, I can achieve the same with:

Stream.periodic(Duration(seconds: 1)).listen((){
setState(){});

as well.

I wonder, which approach is more efficient?
Stream builder returning a single widget or in other cases a widget tree every second. While setState() rebuild whole app widget tree in my case. I am confused here. Please advise.

Solution

setState does not rebuild the whole app widget tree. Both of the methods you mentioned (StreamBuilder & Stream.listen) rebuild themselves and their descendants whenever there is a new event.

If your whole app is under a single big build method, then yes setState will trigger a rebuild of whatever build method it is under. If that is the case you should split up your code for performance reasons.

Your use case is actually mentioned in the official StatefulWidget docs.

Push the state to the leaves. For example, if your page has a ticking clock, rather than putting the state at the top of the page and rebuilding the entire page each time the clock ticks, create a dedicated clock widget that only updates itself.

Additionally, you can always look to take advantage of the devtools to measure any performance differences.

Comments

[ambiguous58]

Could the devtools have a more precise answer?

[omer]

@pskink Seems now questions raises on using StatefulBuilder inside StreamBuilder StreamBuilder will return StatefullBuilder each second. Also, Why we need to setState each seconds as I have already those fields in scope of StreamBuilder. anyways. open to discussion.

[omer]

I do not want to avoid it but was curious about the performance of both method, (StreamBuilder vs Stream.listen(setState(){})) in my particular case. @ambiguous58 pointed out some useful hints below.

[ambiguous58]

I don't think that's accurate since both of the methods OP mentioned (StreamBuilder & Stream.listen) rebuild themselves and their descendants whenever there is a new event.

[Moaid ALRazhy]

yes the descendants of the StreamBuilder in First case will be rebuilt , however in the second it calling setState() will rebuild the entire widget tree even above the widget thet needs to be rebuilt

[ambiguous58]

setState only rebuilds the build method it is under. So if the whole app is under a single big build method then yes it will be rebuilt. *shudder*

[omer]

So, using StreamBuilder seems equivalent to dedicated clock widget in this case. right?

[Moaid ALRazhy]

yes this is what I meant exactly if you have maybe multiple stream Builders in column , then it would be better to use first method since it will build every one according to its state.