在构建期间调用 setState() 或 markNeedsBuild()。在提供者期间

Question

我正在尝试使用提供程序更新流中的当前曲目。 但我收到了下面提到的这个错误

我想做的是每次播放一首新歌曲时，我都想获取该歌曲数据并将其与歌曲列表进行比较，我可以从中显示这首特定歌曲正在播放。无论该列表在树中的哪个位置。

///// 这是提供者调用的类。

import 'package:flutter/foundation.dart';
class MyCurrentTrack with ChangeNotifier{
  String _currentTrack = " ";
  String get currentTrack => _currentTrack;
  set currentTrack(String newValue){
    _currentTrack = newValue;
    notifyListeners();
  }
}

这是我要更新的地方

class MusicPlaeryerMini{
Widget musicPlayerMini(){
return StreamBuilder<PlayerState>(
  stream: SpotifySdk.subscribePlayerState(),
  builder: (BuildContext context, AsyncSnapshot<PlayerState> snapshot) {
    final currentTime = Provider.of<MyCurrentTrack>(context);//called the function here 
    var track = snapshot.data?.track;
    currentTrackImageUri = track?.imageUri;
    var playerState = snapshot.data;
    if(playerState != null){
      currentTime.currentTrack = playerState.track!.uri;// trying to update the value here 
      currentTrackTime = playerState.playbackPosition.toInt();
    }
    if (playerState == null || track == null ) {
      return Center(
          child: Container()
      );
    }

return
  Container(height: 70,
    decoration: const BoxDecoration( color: Colors.amberAccent,
        borderRadius: BorderRadius.all(Radius.circular(18))),
    width: screenWidth(context,dividedBy: 1.05),

    child: Padding(
      padding: const EdgeInsets.symmetric(horizontal: 10,vertical: 0),
      child: Row(
        children: [
          GestureDetector(onTap: (){
            Navigator.push (
              context,
              MaterialPageRoute (
                builder: (BuildContext context) =>  MusicPlayerFull(ispaused: playerState.isPaused,),
              ),
            );
          },
            child: Row(
              children: [
                SizedBox(width: 50,height: 50,
                    child: MusicPlayer().spotifyImageWidget(currentTrackImageUri!)),
                const SizedBox(width: 20),
                SizedBox(
                  width: screenWidth(context,dividedBy: 2.3 ,),
                  child: Column(crossAxisAlignment: CrossAxisAlignment.start,mainAxisAlignment: MainAxisAlignment.center,
                      children : [
                        SizedBox(width:screenWidth(context,dividedBy: 2.2),height: 18,
                            child:Text(track.name,overflow: TextOverflow.ellipsis,style: const TextStyle( fontWeight:FontWeight.bold ,fontSize: 16 ,color: Colors.blue ),
                            )
                        ),
                        Text(track.artist.name!,style:const TextStyle( fontWeight:FontWeight.bold ,fontSize: 16 ,color: Colors.blue ),overflow: TextOverflow.ellipsis)
                      ]),
                ),
              ],),),

          playerState.isPaused
              ? IconButton(
            icon: const Icon(Icons.play_arrow),
            onPressed: MusicPlayer().resume,
          )
              : IconButton(
            icon: const Icon(Icons.pause),
            onPressed: MusicPlayer().pause,
          ),
          IconButton(icon: const Icon(Icons.favorite ,color: Colors.blueGrey,)
            ,onPressed: (){
              MusicPlayer().addToLibrary(track.uri);
            },),
        ],
      ),
    ),
  );
       },
   );
   }
     }

这是错误

    The following assertion was thrown while dispatching notifications for MyCurrentTrack:
setState() or markNeedsBuild() called during build.

This _InheritedProviderScope<MyCurrentTrack?> widget cannot be marked as needing to build because the framework is already in the process of building widgets. A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.
The widget on which setState() or markNeedsBuild() was called was: _InheritedProviderScope<MyCurrentTrack?>
  value: Instance of 'MyCurrentTrack'
  listening to value
The widget which was currently being built when the offending call was made was: StreamBuilder<PlayerState>
  dirty
  dependencies: [MediaQuery, _InheritedProviderScope<MyCurrentTrack?>]
  state: _StreamBuilderBaseState<PlayerState, AsyncSnapshot<PlayerState>>#4483f
When the exception was thrown, this was the stack: 
#0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:4261:11)
#1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:4276:6)
#2      _InheritedProviderScopeElement.markNeedsNotifyDependents (package:provider/src/inherited_provider.dart:570:5)
#3      ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:308:24)
#4      MyCurrentTrack.currentTrack= (package:spotify_sdk_example/schedule.dart:12:5)
#5      MusicPlaeryerMini.musicPlayerMini.<anonymous closure> (package:spotify_sdk_example/widgets/musicPlayerMini.dart:20:23)
#6      StreamBuilder.build (package:flutter/src/widgets/async.dart:442:81)
#7      _StreamBuilderBaseState.build (package:flutter/src/widgets/async.dart:124:48)
#8      StatefulElement.build (package:flutter/src/widgets/framework.dart:4705:27)
#9      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4588:15)
#10     StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4763:11)
#11     Element.rebuild (package:flutter/src/widgets/framework.dart:4311:5)
#12     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2578:33)
#13     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:882:21)
#14     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:363:5)
#15     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1145:15)
#16     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1082:9)
#17     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:996:5)
#21     _invoke (dart:ui/hooks.dart:150:10)
#22     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:270:5)
#23     _drawFrame (dart:ui/hooks.dart:114:31)
(elided 3 frames from dart:async)
The MyCurrentTrack sending notification was: Instance of 'MyCurrentTrack'

Answer 1

您调用 notifyListeners，其中包括在侦听事件提供程序的小部件上调用 setState。这是一个问题，因为当小部件处于重建过程中时，您无法在小部件上调用 setState。

这一行调用提供者时将listen设置为true（这是默认设置），导致框架重新构建UI，即使它当前正在重建（因为它被放置在构建器中），这是被禁止的：

 final currentTime = Provider.of<MyCurrentTrack>(context);

如果您想获取数据一次进行初始化，请将其移到 StreamBuilder 的构建器之外并设置为 false，如下所示：

final currentTime = Provider.of<MyCurrentTrack>(context, listen: false);

否则将其放在 didChangeDependecies 中