AngelCollapsibleBar

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

import 'dart:math' as math;

import 'GradientButton.dart';
import 'main_logo.dart';
import 'CustomNavigation.dart';
import 'StatusNavigationBar.dart';
import 'ExpandibleBar.dart';
import 'ProfileView.dart';


import 'package:flutter/cupertino.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);



  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  GradientAppBar appBARRRR = GradientAppBar(
    title: RaisedButton(child: Text("Hola"),
        onPressed: () {

    }),
    backgroundColors: <Color>[Color(0xFFFD758E), Color(0xFFFD758E)],
  );

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new NestedScrollView(
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return <Widget>[

            SliverPersistentHeader(
              pinned: true,
              delegate: _TestHeader(
                  showHeading: true,
                  expandedHeight: 300.0,
                  collapsedHeight: 80.0
              ),
            ),

          ];
        },
        body: ListView.builder(
          itemCount: 60,
          itemBuilder: (BuildContext context, int index) {
            return new Text('Item $index');
          },
        ),
      ),
    );
  }
}

class _TestHeader extends SliverPersistentHeaderDelegate {
  _TestHeader({
    @required this.collapsedHeight,
    @required this.expandedHeight,
    @required this.showHeading,
  });

  bool showHeading;
  final double expandedHeight;
  final double collapsedHeight;

  @override
  double get minExtent => collapsedHeight;

  @override
  double get maxExtent => math.max(expandedHeight, minExtent);

  @override
  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {
    print(shrinkOffset);
    print("rebuilding headings");
    return FlexibleSpaceBar.createSettings(
        minExtent: minExtent,
        maxExtent: maxExtent,
        currentExtent: math.max(minExtent, maxExtent - shrinkOffset),
        child: Container(
          padding: EdgeInsets.only(top: MediaQuery.of(context).padding.top),
          decoration: BoxDecoration(
            gradient: LinearGradient(
                begin: Alignment.bottomLeft,
                end: Alignment.topRight,
                colors: <Color>[Color(0xFFFD758E), Color(0xFFFD758E)]
            ),
          ),

          child: Transform.scale(
            scale: (((maxExtent - shrinkOffset - MediaQuery.of(context).padding.top) - 15.0) / expandedHeight).clamp(0.0, 1.0),
            child: Column(
              children: <Widget>[
                Row(
                  children: <Widget>[
                    Text("Test1"),
                    Text("Test1"),
                    Text("Test1"),
                    Text("Test1")
                  ],
                ),

                RaisedButton(child: Text("Keen"),onPressed: () {
                  print("Commander");
                }),
                Text("B")
              ],
            ),
          ),
        )
    );
  }

  @override
  bool shouldRebuild(_TestHeader oldDelegate) {
    return expandedHeight != oldDelegate.expandedHeight ||
        collapsedHeight != oldDelegate.collapsedHeight;
  }
}