feat: ProgressBar shows position in song

lib/level.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:io';
 
 import 'package:flutter/material.dart';
@@ -12,44 +13,98 @@ class Level extends StatefulWidget {
 }
 
 class _LevelState extends State<Level> {
-  final _player = AudioPlayer();
+  final player = AudioPlayer();
   bool _isPlaying = true;
+  Duration? _duration;
+  Duration? _position;
+
+  StreamSubscription? _durationSubscription;
+  StreamSubscription? _positionSubscription;
+
+  @override
+  void setState(VoidCallback fn) {
+    // Subscriptions only can be closed asynchronously,
+    // therefore events can occur after widget has been disposed.
+    if (mounted) {
+      super.setState(fn);
+    }
+  }
+
+  @override
+  void initState() {
+    super.initState();
+    // Use initial values from player
+    player.getDuration().then(
+          (value) => setState(() {
+            _duration = value;
+          }),
+        );
+    player.getCurrentPosition().then(
+          (value) => setState(() {
+            _position = value;
+          }),
+        );
+    _durationSubscription = player.onDurationChanged.listen((duration) {
+      setState(() => _duration = duration);
+    });
+
+    _positionSubscription = player.onPositionChanged.listen(
+      (p) => setState(() => _position = p),
+    );
+  }
 
   @override
   Widget build(BuildContext context) {
+    player.onDurationChanged.listen((Duration d) {
+      // print('Max duration: $d');
+      setState(() => _duration = d);
+    });
+
+    player.onPositionChanged.listen((Duration p) {
+      // print('Current position: $p');
+      setState(() => _position = p);
+    });
+
     String audioPath = Directory(widget.stepmaniaFolderPath)
         .listSync()
         .firstWhere((entity) => entity.path.endsWith('.ogg'),
             orElse: () => File(''))
         .path;
-    _player.play(DeviceFileSource(audioPath));
+    player.play(DeviceFileSource(audioPath));
     return Scaffold(
         appBar: AppBar(
           leading: IconButton(
             icon: Icon(_isPlaying ? Icons.pause : Icons.play_arrow),
-            onPressed: () => {
-              if (_isPlaying)
-                {
-                  _player.pause(),
-                  setState(() {
-                    _isPlaying = false;
-                  })
-                }
-              else
-                {
-                  _player.resume(),
-                  setState(() {
-                    _isPlaying = true;
-                  })
-                },
+            onPressed: () {
+              if (_isPlaying) {
+                player.pause();
+                setState(() {
+                  _isPlaying = false;
+                });
+              } else {
+                player.resume();
+                setState(() {
+                  _isPlaying = true;
+                });
+              }
             },
           ),
-          title: Text('Level 1'),
+          title: Text(widget.stepmaniaFolderPath.split('/').last),
           actions: [
             IconButton(
                 icon: Icon(Icons.close),
                 onPressed: () => Navigator.pop(context))
           ],
+          bottom: PreferredSize(
+              preferredSize: Size(double.infinity, 1.0),
+              child: LinearProgressIndicator(
+                value: (_duration != null &&
+                        _position != null &&
+                        _position!.inMilliseconds > 0 &&
+                        _position!.inMilliseconds < _duration!.inMilliseconds)
+                    ? _position!.inMilliseconds / _duration!.inMilliseconds
+                    : 0.0,
+              )),
         ),
         body: Stack(children: [
           Arrow(
@@ -91,7 +146,9 @@ class _LevelState extends State<Level> {
 
   @override
   void dispose() {
-    _player.dispose();
+    _durationSubscription?.cancel();
+    _positionSubscription?.cancel();
+    player.dispose();
     super.dispose();
   }
 }