is it right way to handle variables inside @build method in flutter?

Question

i think sometimes it is required to handle variables inside @override build method.

@override
  Widget build(BuildContext context) {
    Animation animationTitle1 = Tween<double>(begin: 0.0, end: 1.0).animate(
        CurvedAnimation(
            parent: widget.animationController,
            curve: Interval(0, 1.0, curve: Curves.fastOutSlowIn)));
    Animation animationTitle2 = Tween<double>(begin: 0.0, end: 1.0).animate(
        CurvedAnimation(
            parent: widget.animationController,
            curve: Interval(0.2, 1.0, curve: Curves.fastOutSlowIn)));
.
.
.

i don't know it is logically efficient or not ? but somehow i need this kind of logic to declare and manage multiple variables inside @build method. some requirements like

• animations objects
• call stream builder widget manually in some case to refresh the data

example like

@override
  Widget build(BuildContext context) {
    var streamBuilder = StreamBuilder(
          stream: myStreamObj,
          builder: (BuildContext context, AsyncSnapshot<dynamic> snapshotVacchan) {
           // my code
          },
        );
    
    return Column(
            children: [
              streamBuilder,
              FlatButton(
                  child: Text('Reload'),
                  onPressed: () {
                    setState(() {
                      myStreamObj = newScreen;
                    });
                  }),
            ],
          );
 }

Solution

According to my knowledge, it is not the proper way of coding to declare or manage variables inside the build method.