ESSE/lib/utils/toast.dart

import 'package:flutter/material.dart';

class FadeToast extends StatefulWidget {
  final Widget child;

  FadeToast({Key key, this.child}) : super(key: key);

  @override
  _FadeToastState createState() => _FadeToastState();
}

class _FadeToastState extends State<FadeToast> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation _animation;

  @override
  void initState() {
    _controller = AnimationController(vsync: this, duration: Duration(seconds: 1));
    _animation = Tween(begin: 0.0, end: 1.0).animate(_controller);
    _animation.addStatusListener((status){
        if(status == AnimationStatus.completed){
          Future.delayed(Duration(seconds: 2), () {
              _controller.reverse();
          });

        }
    });
    _controller.forward();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return FadeTransition(
      opacity: _animation,
      child: widget.child,
    );
  }
}

void toast(BuildContext context, String text) {
  final scaffold = Scaffold.of(context);
  final color = Theme.of(context).colorScheme;

  scaffold.showSnackBar(
    SnackBar(
      content: FadeToast(
        child: Container(
          decoration: BoxDecoration(
            color: Color(0xFFADB0BB).withOpacity(0.5),
            borderRadius: BorderRadius.circular(25.0)
          ),
          height: 50.0,
          margin: EdgeInsets.only(bottom: 40.0),
          alignment: Alignment.center,
          padding: const EdgeInsets.all(10.0),
          child: Text(text, style: TextStyle(color: color.onPrimary)),
      )),
      backgroundColor: Colors.transparent, elevation: 1000, behavior: SnackBarBehavior.floating,
      duration: Duration(seconds: 4),
    )
  );
}