main.dart

import 'package:flutter/material.dart';

const _tabletBreakpoint = 720.0;
const _desktopBreakpoint = 1440.0;
const _minHeight = 400.0;
const _tabletSpacingVertical = 15.0;
const _tabletSpacingHorizontial = 10.0;
const _drawerWidth = 304.0;

class NavigationRail extends StatelessWidget {
  final FloatingActionButton floatingActionButton;
  final int currentIndex;
  final Widget body;
  final Widget title;
  final ValueChanged<int> onTap;
  final List<BottomNavigationBarItem> tabs;
  final WidgetBuilder drawerHeaderBuilder, drawerFooterBuilder;
  final Color bottomNavigationBarColor;
  final double tabletBreakpoint, desktopBreakpoint, minHeight, drawerWidth;
  final List<Widget> actions;
  final BottomNavigationBarType bottomNavigationBarType;
  final Color bottomNavigationBarSelectedColor,
      bottomNavigationBarUnselectedColor;
  final bool isDense;

  const NavigationRail({
    Key key,
    @required this.currentIndex,
    @required this.tabs,
    @required this.onTap,
    this.actions,
    this.isDense = false,
    this.floatingActionButton,
    this.drawerFooterBuilder,
    this.drawerHeaderBuilder,
    this.body,
    this.title,
    this.bottomNavigationBarColor,
    this.tabletBreakpoint = _tabletBreakpoint,
    this.desktopBreakpoint = _desktopBreakpoint,
    this.drawerWidth = _drawerWidth,
    this.bottomNavigationBarType = BottomNavigationBarType.fixed,
    this.bottomNavigationBarSelectedColor,
    this.bottomNavigationBarUnselectedColor,
    this.minHeight = _minHeight,
  }) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Directionality(
      textDirection: Directionality.of(context),
      child: LayoutBuilder(
        builder: (_, dimens) {
          final _direction = Directionality.of(context);
          final isRtl = _direction == TextDirection.rtl;
          if (dimens.maxWidth >= desktopBreakpoint &&
              dimens.maxHeight > minHeight) {
            return Material(
              color: Theme.of(context).scaffoldBackgroundColor,
              child: Row(
                children: <Widget>[
                  Container(
                    width: _drawerWidth,
                    child: _buildDrawer(context, true),
                  ),
                  Expanded(
                    child: Stack(
                      alignment: Alignment.topCenter,
                      children: <Widget>[
                        Positioned.fill(
                          child: Scaffold(
                            appBar: AppBar(
                              title: title,
                              actions: actions,
                              automaticallyImplyLeading: false,
                            ),
                            body: body,
                          ),
                        ),
                        if (floatingActionButton != null) ...[
                          Positioned(
                            top: kToolbarHeight - kToolbarHeight / 2,
                            right: isRtl ? null : kToolbarHeight / 2,
                            left: !isRtl ? null : kToolbarHeight / 2,
                            child: floatingActionButton,
                            width: 50,
                            height: 50,
                          )
                        ],
                      ],
                    ),
                  ),
                ],
              ),
            );
          }
          if (dimens.maxWidth >= tabletBreakpoint &&
              dimens.maxHeight > minHeight) {
            return Scaffold(
              appBar: AppBar(
                title: title,
                actions: actions,
                automaticallyImplyLeading: true,
              ),
              drawer: drawerHeaderBuilder != null || drawerFooterBuilder != null
                  ? _buildDrawer(context, false)
                  : null,
              body: Row(
                children: <Widget>[
                  Container(
                    child: Column(
                      children: <Widget>[
                        if (floatingActionButton != null) ...[
                          Padding(
                            padding: const EdgeInsets.symmetric(
                              vertical: _tabletSpacingVertical,
                              horizontal: _tabletSpacingHorizontial,
                            ),
                            child: floatingActionButton,
                          ),
                        ],
                        for (var tab in tabs) ...[
                          Padding(
                            padding: const EdgeInsets.symmetric(
                              vertical: _tabletSpacingVertical,
                              horizontal: _tabletSpacingHorizontial,
                            ),
                            child: _buildTab(currentIndex == tabs.indexOf(tab),
                                context, tab),
                          ),
                        ],
                      ],
                    ),
                  ),
                  Expanded(child: body),
                ],
              ),
            );
          }
          return Scaffold(
            appBar: AppBar(
              title: title,
              actions: actions,
              automaticallyImplyLeading: true,
            ),
            drawer: drawerHeaderBuilder != null || drawerFooterBuilder != null
                ? _buildDrawer(context, false)
                : null,
            body: body,
            floatingActionButton: floatingActionButton,
            floatingActionButtonLocation: FloatingActionButtonLocation.endFloat,
            bottomNavigationBar: BottomNavigationBar(
              type: bottomNavigationBarType,
              backgroundColor: bottomNavigationBarColor,
              currentIndex: currentIndex,
              onTap: onTap,
              items: tabs,
              unselectedItemColor: bottomNavigationBarUnselectedColor,
              selectedItemColor: bottomNavigationBarSelectedColor,
            ),
          );
        },
      ),
    );
  }

  Widget _buildTab(
      bool selected, BuildContext context, BottomNavigationBarItem item) {
    final _theme = Theme.of(context);
    final _isDark = _theme.brightness == Brightness.dark;
    final _color = selected
        ? _isDark ? Colors.tealAccent[200] : _theme.primaryColor
        : Colors.grey;
    final _iconTheme = IconThemeData(
      color: _color,
      size: _theme.iconTheme.size,
      opacity: _theme.iconTheme.opacity,
    );
    final _icon = Align(
      alignment: Alignment.topCenter,
      heightFactor: 1.0,
      child: IconTheme(
        data: _iconTheme,
        child: selected ? item.activeIcon : item.icon,
      ),
    );
    if (isDense) {
      return InkWell(
        onTap: () => onTap(tabs.indexOf(item)),
        child: Padding(
          padding: const EdgeInsets.all(8.0),
          child: _icon,
        ),
      );
    }
    return InkWell(
      onTap: () => onTap(tabs.indexOf(item)),
      child: Column(
        children: <Widget>[
          _icon,
          Container(height: 4.0),
          DefaultTextStyle(
            style: TextStyle(color: _color),
            child: item?.title,
          ),
        ],
      ),
    );
  }

  Widget _buildDrawer(BuildContext context, bool showTabs) {
    return Drawer(
      child: SafeArea(
        child: SingleChildScrollView(
          child: Column(
            children: <Widget>[
              if (drawerHeaderBuilder != null) ...[
                drawerHeaderBuilder(context),
              ],
              if (showTabs) ...[
                for (var tab in tabs) ...[
                  ListTile(
                    dense: isDense,
                    selected: currentIndex == tabs.indexOf(tab),
                    leading: tab?.icon,
                    title: tab?.title,
                    onTap: () => onTap(tabs.indexOf(tab)),
                  ),
                ]
              ],
              if (drawerFooterBuilder != null) ...[
                drawerFooterBuilder(context),
              ],
            ],
          ),
        ),
      ),
    );
  }
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'NavigationRail Demo',
      theme: _theme(ThemeData.light().copyWith(
        accentColor: Colors.red,
      )),
      home: MyHomePage(title: 'Navigation Rail Demo'),
    );
  }

  ThemeData _theme(ThemeData base) {
    return ThemeData(
      primarySwatch: Colors.blue,
      appBarTheme: base.appBarTheme.copyWith(elevation: 0.0),
      floatingActionButtonTheme: base.floatingActionButtonTheme.copyWith(
        elevation: 2.0,
        backgroundColor: base.accentColor,
      ),
    );
  }
}

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

  final String title;

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

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

  @override
  Widget build(BuildContext context) {
    return NavigationRail(
      drawerHeaderBuilder: (context) {
        return Column(
          children: <Widget>[
            UserAccountsDrawerHeader(
              accountName: Text("Steve Jobs"),
              accountEmail: Text("jobs@apple.com"),
            ),
          ],
        );
      },
      drawerFooterBuilder: (context) {
        return Column(
          children: <Widget>[
            ListTile(
              leading: Icon(Icons.settings),
              title: Text("Settings"),
            ),
            ListTile(
              leading: Icon(Icons.info_outline),
              title: Text("About"),
            ),
          ],
        );
      },
      currentIndex: _currentIndex,
      onTap: (val) {
        if (mounted)
          setState(() {
            _currentIndex = val;
          });
      },
      title: Text(widget.title),
      body: IndexedStack(
        index: _currentIndex,
        children: <Widget>[
          Container(color: Colors.blue[300]),
          Container(color: Colors.red[300]),
          Container(color: Colors.purple[300]),
          Container(color: Colors.grey[300]),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {},
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
      tabs: <BottomNavigationBarItem>[
        BottomNavigationBarItem(
          title: Text("Folders"),
          icon: Icon(Icons.folder),
        ),
        BottomNavigationBarItem(
          title: Text("History"),
          icon: Icon(Icons.history),
        ),
        BottomNavigationBarItem(
          title: Text("Gallery"),
          icon: Icon(Icons.photo_library),
        ),
        BottomNavigationBarItem(
          title: Text("Camera"),
          icon: Icon(Icons.camera),
        ),
      ],
    );
  }
}