درخواست راهنمایی برای چند برطرف کردن چند ارور

سلام خسته نباشید
من از این پلاگین استفاده میکنم : https://pub.dev/packages/flutter_sound
وقتی اولین بار روی دکمه پلی میزنم این رور رو میده و یه 2-3 ثانیه برنامه هنگ میکنه و سنگین میشه تا آهنگ پلی بشه.

E/flutter ( 6408): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The getter 'stream' was called on null.
E/flutter ( 6408): Receiver: null
E/flutter ( 6408): Tried calling: stream
E/flutter ( 6408): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
E/flutter ( 6408): #1      FlutterSound.onPlayerStateChanged (package:flutter_sound/flutter_sound.dart:16:68)
E/flutter ( 6408): #2      _ShowProductPageState.seek (package:alimelodi/pages/show_product.dart:107:40)
E/flutter ( 6408): <asynchronous suspension>
E/flutter ( 6408): #3      _ShowProductPageState._setTimer.<anonymous closure> (package:alimelodi/pages/show_product.dart:51:9)
E/flutter ( 6408): #4      _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter ( 6408): #5      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 6408): #6      _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter ( 6408): #7      _CustomZone.bindUnaryCallbackGuarded.<anonymous closure> (dart:async/zone.dart:968:26)
E/flutter ( 6408): #8      _rootRunUnary (dart:async/zone.dart:1136:13)
E/flutter ( 6408): #9      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 6408): #10     _CustomZone.bindUnaryCallback.<anonymous closure> (dart:async/zone.dart:952:26)
E/flutter ( 6408): #11     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
E/flutter ( 6408): #12     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
E/flutter ( 6408): #13     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:171:12)
E/flutter ( 6408): 
I/Choreographer( 6408): Skipped 81 frames!  The application may be doing too much work on its main thread.

این هم اروری هست که موقع بستن صفحه و فراخوانی متد dispose هست

E/flutter ( 6408): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The getter 'currentPosition' was called on null.
E/flutter ( 6408): Receiver: null
E/flutter ( 6408): Tried calling: currentPosition
E/flutter ( 6408): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
E/flutter ( 6408): #1      _ShowProductPageState.seek.<anonymous closure> (package:alimelodi/pages/show_product.dart:108:26)
E/flutter ( 6408): #2      _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter ( 6408): #3      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 6408): #4      _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter ( 6408): #5      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
E/flutter ( 6408): #6      _DelayedData.perform (dart:async/stream_impl.dart:591:14)
E/flutter ( 6408): #7      _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
E/flutter ( 6408): #8      _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:667:7)
E/flutter ( 6408): #9      _rootRun (dart:async/zone.dart:1120:38)
E/flutter ( 6408): #10     _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 6408): #11     _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 6408): #12     _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:963:23)
E/flutter ( 6408): #13     _rootRun (dart:async/zone.dart:1124:13)
E/flutter ( 6408): #14     _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 6408): #15     _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 6408): #16     _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:963:23)
E/flutter ( 6408): #17     _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
E/flutter ( 6408): #18     _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
E/flutter ( 6408): 

اینم کد برنامه :

 @override
  initState() {
    super.initState();
    flutterSound = new FlutterSound();
    _setTimer();
  }

  _setTimer() {
    timer = Timer.periodic(new Duration(seconds: 1), (Timer t) {
      if (isPlaying) {
        seek();
      }
      setState(() {
        if (duration == 0.0 || position == 0.0) {
          seekValue = 0.0;
        } else {
          seekValue = (100.0 * position) / duration;
        }
      });
    });
  }

  @override
  void dispose() {
    timer?.cancel();
    if(position!=0){
      stop2();
    }
    super.dispose();
  }

  Future<void> play(String url) async {
    String path = await flutterSound.startPlayer(url);
    await flutterSound.setVolume(1.0);
    print('startPlayer: $path');

    if (isPlaying) {
      seek();
    }

    _playerSubscription = flutterSound.onPlayerStateChanged.listen((e) {
      if (e != null) {
        duration = e.duration;
      }
    });

  }

  Future<void> pause() async {
    String result = await flutterSound.pausePlayer();
    print('pausePlayer: $result');
  }

  Future<void> stop2() async {
    String result = await flutterSound.stopPlayer();
    print('stopPlayer: $result');
  }

  Future<void> stop() async {
    String result = await flutterSound.stopPlayer();
    print('stopPlayer: $result');
    setState(() {
      position = 0;
    });
  }

  Future<void> seek() async {
    _playerSubscription = flutterSound.onPlayerStateChanged.listen((p) {
      if (isPlaying && p.currentPosition + 200.0 >= p.duration) {
        seekToSecond(0);
        stop();
        setState(() {
          isPlaying = false;
        });
      }

      setState(() {
        position = p.currentPosition;
      });

      if (isPlaying) {
        setState(() {
          duration = p.duration;
        });
      }

      if (position != 0.0) {
        setState(() {
          isLoadingToPlay = false;
        });
      }
    });

    print('D = ${duration.toString()}');
    print('P = ${position.toString()}');
  }

  Future<void> seekToSecond(int milliSecond) async {
    await flutterSound.seekToPlayer(milliSecond);
  }

ممنون میشم بگین باید چیکار کنم!
@hesammousavi
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