import 'package:flutter/material.dart';



void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.light(),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: TriangleError(),
        ),
      ),
    );
  }
}

class TriangleError extends StatefulWidget {
  const TriangleError({Key key}) : super(key: key);

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

class _TriangleErrorState extends State<TriangleError>
    with TickerProviderStateMixin {
  AnimationController rotationController;

  @override
  void initState() {
    rotationController = AnimationController(
      duration: const Duration(milliseconds: 2000),
      vsync: this,
    )..repeat();

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: EdgeInsets.all(10),
      child: Center(
        child: AspectRatio(
          aspectRatio: 1,
          child: Stack(
            children: <Widget>[
              Align(
                alignment: Alignment.center,
                child: RotationTransition(
                  turns:
                      Tween(begin: 0.0, end: 1.0).animate(rotationController),
                  child: ClipPath(
                    clipper: TrianglePath(),
                    child: LayoutBuilder(
                      builder: (context, constrains) {
                        return Container(
                          // uncomment and reload view
                          // color: Colors.red,
                          decoration: BoxDecoration(
                            gradient: LinearGradient(
                              colors: [
                                Theme.of(context).primaryColorLight,
                                Theme.of(context)
                                    .primaryColorLight
                                    .withAlpha(10)
                              ],
                              begin: Alignment.bottomCenter,
                              end: Alignment.topCenter,
                            ),
                          ),
                          margin: EdgeInsets.all(constrains.maxHeight / 8),
                        );
                      },
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class TrianglePath extends CustomClipper<Path> {
  var radius = 10.0;
  @override
  Path getClip(Size size) {
    Path path = Path();
    path.lineTo(size.width / 4, 0);
    path.lineTo(size.width / 2, size.height / 2);
    path.lineTo(size.width - size.width / 4, 0);

    path.lineTo(0, 0);
    return path;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) => false;
}