import 'package:flutter/material.dart';

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

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  bool _pinned = true;
  bool _snap = false;
  bool _floating = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        slivers: <Widget>[
          //sliversのリストにSliverAppBarを設定する
          SliverAppBar(
            pinned: _pinned,
            snap: _snap,
            floating: _floating,
            //appbarの高さを設定
            expandedHeight: 200.0,
            //appbar内に表示するウィジェットを設定
            flexibleSpace: FlexibleSpaceBar(
              title: Text(widget.title),
              background: FlutterLogo(),
            ),
          ),
          SliverFixedExtentList(
            //子ウィジェットの高さを設定
            itemExtent: 150.0,
            delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) {
                return Container(
                  alignment: Alignment.center,
                  color: Colors.lightBlue[100 * (index % 9)],
                  child: Text("list item $index"),
                );
              },
              //子ウィジェットの表示数を設定
              childCount: 10,
            ),
          ),
        ],
      ),
      //画面下部にナビゲーションバーを表示する
      bottomNavigationBar: BottomAppBar(
        child: Padding(
          padding: const EdgeInsets.all(8.0),
          child: OverflowBar(
            overflowAlignment: OverflowBarAlignment.center,
            children: <Widget>[
              Row(
                mainAxisSize: MainAxisSize.min,
                children: <Widget>[
                  const Text("pinned"),
                  //スイッチでpinnedをON/OFFできるようにする
                  Switch(
                    value: _pinned,
                    onChanged: (bool value) {
                      setState(
                        () {
                          _pinned = value;
                        },
                      );
                    },
                  ),
                ],
              ),
              Row(
                mainAxisSize: MainAxisSize.min,
                children: <Widget>[
                  const Text("snap"),
                  Switch(
                    value: _snap,
                    onChanged: (bool value) {
                      setState(() {
                        _snap = value;
                        //スナップはFloatingが有効の時だけ使える
                        _floating = _floating || _snap;
                      });
                    },
                  ),
                ],
              ),
              Row(
                mainAxisSize: MainAxisSize.min,
                children: [
                  const Text("floating"),
                  Switch(
                    value: _floating,
                    onChanged: (bool value) {
                      setState(() {
                        _floating = value;
                        _snap = _floating && _snap;
                      });
                    },
                  ),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }
}