@override
Widget build(BuildContext context) {
 return new RaisedButton(
  onPressed: () {
  print("click");
  },
  child: new Text("Button"));
}

class SampleApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
 return new Scaffold(
  body: new Center(
  child: new GestureDetector(
  child: new FlutterLogo(
   size: 200.0,
  ),
  onTap: () {
   print("tap");
  },
  ),
 ));
 }
}

void main() => runApp(DemoApp());

class DemoApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  title: '導(dǎo)航演示1',
  home: new MyAppHome(),
 );
 }
}

class MyAppHome extends StatefulWidget{
 @override
 _MyAppHomeState createState() => _MyAppHomeState();

}
class _MyAppHomeState extends State<MyAppHome> with TickerProviderStateMixin{
 AnimationController controller;
 CurvedAnimation curve;

 @override
 void initState() {
 super.initState();
 controller = new AnimationController(
  duration: const Duration(milliseconds: 2000), vsync: this);
 curve = new CurvedAnimation(parent: controller, curve: Curves.easeIn);
 }

 @override
 Widget build(BuildContext context) {
 return new Scaffold(
  body: new Center(
  child: new GestureDetector(
  child: new RotationTransition(
   turns: curve,
   child: new FlutterLogo(
    size: 200.0,
   )),
  onDoubleTap: () {
   if (controller.isCompleted) {
   controller.reverse();
   } else {
   controller.forward();
   }
  },
  ),
 ));
 }
}