Flutter - Is there any way to change variable value without using setState() or notifyListeners()

Question

I want to ask if there is any other way than using SetState() or notifyListener() to change the value of bool. Because using setState() or notifyListener() crashes app for some seconds. actually i m using NotificationListener to change the value of bool on user scroll. Please help

Answer 1

use stream.it is like a pipe you add value from a side (Sink) and recieve it on the other side (Stream).i will try to explain it:

  //make a stream controller
  StreamController<bool> valueController = StreamController();
  
  //this will listen to every new value you add
  Stream valueOutput = valueController.stream;

  //you can add new values throw the sink
   Sink valueInput = valueController.sink;

so when you want to add a value to the stream just call

valueInput.add(true);//add whatever booleon value you want

and then recieve it by calling

 valueOutput.listen((value) {
   //this function will be invoked every time you add a new value.
 });

or you can add StreamBuilder if you want to rebuild a specific widget based on that boolean value

StreamBuilder(
      stream: valueOutput,
      builder: (context,snapshot) {

       bool value = snapshot.data;
       log(value.toString());//true or false

       return yourWidget();
    })

i hope i explained it well, good luck with your problem.

i think when you use setState it rebuilds the entire screen and if you are using scroll controller to listen to user`s scroll then the screen will rebuild every pixel user scrolls so that is a lot of rendering. maybe share some code snippet of your code so we can help.