Animated Opacity

 import "package:flutter/material.dart";

void main()
{
  runApp(const MyApp());
}
class MyApp extends StatelessWidget
{
  const MyApp({super.key});

  @override
  Widget build(BuildContext context)
  {
    return MaterialApp(
      title: "hello",
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.brown,
      ),
      home: const FlutterApp(),
    );
  }
}
class FlutterApp extends StatefulWidget
{
  const FlutterApp({super.key});

  @override
  State<FlutterApp> createState()
  {
    return FlutterState();
  }
}
class FlutterState extends State<FlutterApp>
{
  var myOpacity = 1.0;
  bool isVisible = true;

  @override
  Widget build(BuildContext context)
  {
    return Scaffold(
      drawer: const Drawer(),
      appBar: AppBar(
        title: const Text("Flutter Animated Opacity",
          style: TextStyle(fontWeight: FontWeight.bold),
        ),
        centerTitle: true,
        backgroundColor: Colors.grey,
      ),
      body: SingleChildScrollView(
        child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              AnimatedOpacity(
                duration: const Duration(seconds: 1,),
                opacity: myOpacity,
                //curve: Curves.slowMiddle,
                //curve: Curves.elasticIn,
                //curve: Curves.elasticOut,
                curve: Curves.bounceInOut,
                child: Container(
                  width: 300,
                  height: 400,
                  color: Colors.blue.shade100,
                  child: const FlutterLogo(size: 200,),
                ),
              ),
              const SizedBox(height: 70,),
        
              ElevatedButton(
                onPressed: (){
                  setState((){
                    
                    if(isVisible)
                      {
                        myOpacity = 0.0;
                        isVisible = false;
                      } else {
                      myOpacity = 1.0;
                      isVisible = true;
                    }
                  },);
                },
                style: ElevatedButton.styleFrom(
                  backgroundColor: Colors.blue,
                  fixedSize: const Size(350.0,50.0),
                ),
                child: const Text("Close",
                  style: TextStyle(fontWeight: FontWeight.bold, fontSize: 20.0, color: Colors.white),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}