Move more code from mobile to common

common/lib/src/app.dart

@@ -0,0 +1,188 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+import 'backend.dart';
+import 'screens/home.dart';
+import 'settings.dart';
+import 'platform.dart';
+import 'playback.dart';
+import 'widgets/player_bar.dart';
+
+/// The classical music player and organizer.
+///
+/// This widget is the cross platform abstraction for a whole Musicus app. The
+/// properties should be implemented seperately for each platform.
+class MusicusApp extends StatelessWidget {
+  /// Path to the database file.
+  final String dbPath;
+
+  /// An object to persist the settings.
+  final MusicusSettingsStorage settingsStorage;
+
+  /// An object handling playback.
+  final MusicusPlayback playback;
+
+  /// An object handling platform dependent functionality.
+  final MusicusPlatform platform;
+
+  MusicusApp({
+    @required this.dbPath,
+    @required this.settingsStorage,
+    @required this.playback,
+    @required this.platform,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return MusicusBackend(
+      dbPath: dbPath,
+      settingsStorage: settingsStorage,
+      playback: playback,
+      platform: platform,
+      child: Builder(
+        builder: (context) {
+          final backend = MusicusBackend.of(context);
+
+          return MaterialApp(
+            title: 'Musicus',
+            theme: ThemeData(
+              brightness: Brightness.dark,
+              accentColor: Colors.amber,
+              textSelectionColor: Colors.grey[600],
+              cursorColor: Colors.amber,
+              textSelectionHandleColor: Colors.amber,
+              toggleableActiveColor: Colors.amber,
+              // Added for sliders and FABs. Not everything seems to obey this.
+              colorScheme: ColorScheme.dark(
+                primary: Colors.amber,
+                secondary: Colors.amber,
+              ),
+              snackBarTheme: SnackBarThemeData(
+                backgroundColor: Colors.grey[800],
+                contentTextStyle: TextStyle(
+                  color: Colors.white,
+                ),
+                behavior: SnackBarBehavior.floating,
+              ),
+              fontFamily: 'Libertinus Sans',
+            ),
+            home: Builder(
+              builder: (context) {
+                if (backend.status == MusicusBackendStatus.loading) {
+                  return Material(
+                    color: Theme.of(context).scaffoldBackgroundColor,
+                  );
+                } else if (backend.status == MusicusBackendStatus.setup) {
+                  return Material(
+                    color: Theme.of(context).scaffoldBackgroundColor,
+                    child: Column(
+                      mainAxisAlignment: MainAxisAlignment.center,
+                      children: <Widget>[
+                        Text(
+                          'Choose the base path for\nyour music library.',
+                          textAlign: TextAlign.center,
+                          style: Theme.of(context).textTheme.headline6,
+                        ),
+                        SizedBox(
+                          height: 16.0,
+                        ),
+                        ListTile(
+                          leading: const Icon(Icons.folder_open),
+                          title: Text('Choose path'),
+                          onTap: () async {
+                            final uri = await platform.chooseBasePath();
+                            if (uri != null) {
+                              backend.settings.setMusicLibraryPath(uri);
+                            }
+                          },
+                        ),
+                      ],
+                    ),
+                  );
+                } else {
+                  return Content();
+                }
+              },
+            ),
+          );
+        },
+      ),
+    );
+  }
+}
+
+class Content extends StatefulWidget {
+  @override
+  _ContentState createState() => _ContentState();
+}
+
+class _ContentState extends State<Content> with SingleTickerProviderStateMixin {
+  final nestedNavigator = GlobalKey<NavigatorState>();
+
+  AnimationController playerBarAnimation;
+  MusicusBackendState backend;
+  StreamSubscription<bool> playerActiveSubscription;
+
+  @override
+  void initState() {
+    super.initState();
+
+    playerBarAnimation = AnimationController(
+      vsync: this,
+      duration: Duration(milliseconds: 300),
+    );
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+
+    backend = MusicusBackend.of(context);
+    playerBarAnimation.value = backend.playback.active.value ? 1.0 : 0.0;
+
+    if (playerActiveSubscription != null) {
+      playerActiveSubscription.cancel();
+    }
+
+    playerActiveSubscription = backend.playback.active.listen((active) =>
+        active ? playerBarAnimation.forward() : playerBarAnimation.reverse());
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // The nested Navigator is for every screen from which the player bar at
+    // the bottom should be accessible. The WillPopScope widget intercepts
+    // taps on the system back button and redirects them to the nested
+    // navigator.
+    return WillPopScope(
+      onWillPop: () async => !(await nestedNavigator.currentState.maybePop()),
+      child: Scaffold(
+        body: Navigator(
+          key: nestedNavigator,
+          onGenerateRoute: (settings) => settings.name == '/'
+              ? MaterialPageRoute(
+                  builder: (context) => HomeScreen(),
+                )
+              : null,
+          initialRoute: '/',
+        ),
+        bottomNavigationBar: SizeTransition(
+          sizeFactor: CurvedAnimation(
+            curve: Curves.easeOut,
+            parent: playerBarAnimation,
+          ),
+          axisAlignment: -1.0,
+          child: PlayerBar(),
+        ),
+      ),
+    );
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    playerActiveSubscription.cancel();
+  }
+}