How to delete data from StreamBuilder after reading? - flutter

Question

I want to delete data from my stream after I read it.
Basically I want the same system than channel in Go.
So, if I add 5, 3 and 2, my stream contains 5, 3 and 2.
When I start reading, I get 5, and my stream now contains 3 and 2 etc...
Is it possible?
EDIT: Here my problem with some code.
I use a StreamBuilder to receive data. When I change the state, it trigger again my function like if I'd just receive data.
child: StreamBuilder<Tag>(
stream: widget.tagStream,
initialData: Tag(),
builder: (BuildContext context, AsyncSnapshot<Tag> snapshot) {
/// This should be trigger only when I receive data
if (mapController.ready && snapshot.hasData) {
tag = snapshot.data;
mapController.move(
LatLng(tag.position.latitude, tag.position.longitude),
mapController.zoom);
}
return RubberBottomSheet(...);
),
Here some context:
I have a map with icons representing objects. When I click on an icon or if I search the item related on my search bar, a RubberBottomSheet appears to show informations about the object. To do that, I use a StreamBuilder, so I just need to put the object clicked or searched in it to make my rubber appears and fill in. I also need to centrer on my icon to let the user know where is the object. My problem is that when I open or close my keyboard or when I use a setState (for changing the appearance of my search bar for example), it automatically trigger the StreamBuilder like if it receive new data.
Sorry, I should have started here...

Answer 1

The answer of Amine seems to be the best, but I'd like to share my solution too, maybe it'll help some persons.
After I've executed my code, I pass an empty object to my Stream. I just have to verify that my object is not empty before executing my code and everything works like a charm.
builder: (BuildContext context, AsyncSnapshot<Tag> snapshot) {
if (mapController.ready &&
snapshot.hasData &&
snapshot.data.mobile.nid != 0) {
tag = snapshot.data;
... /// My code
widget.tagStream.sink.add(Tag());
}

Answer 2

I've had similar behavior with a StreamBuilder and I couldn't find a solution for days. What I did instead is use a ListView builder that takes data from an InheritedWidget instead.
So basically instead of having to put data into the stream sink, I simply wrap my data setter in the InheritedWidget in a setState() and the ListView rebuilds every time I change the data.
N.B: My StreamBuilder also involved a map, I've always thought it was the one interfering with it but I never got to solve the problem. As in your case, every time I change the state, the stream rebuilds with the same data it had before.

Answer 3

Have similar problem in my app.
Workaroung I found is quite simple - global variable, which by default will do nothing ("false" in this example).
But in method which need to call setState() change this variable value to block next snapshot.data when rebuilding widget (in this example value "true" will block).
Remember to change variable to default value or you won't get new stream updates.
// global variable - doing nothing by default
bool _clear = false;
(...)
/// Add additional condition
if (mapController.ready && snapshot.hasData && !_clear) {
tag = snapshot.data;
mapController.move(
LatLng(tag.position.latitude, tag.position.longitude),
mapController.zoom);
}
/// change variable to default value
_clear = false;
return RubberBottomSheet(...);
),
(...)
// some method calling setState
void _clearMethod() {
_clear = true;
setState(() {});
}