Google maps 为什么我会得到_state！=_PlatformViewState.disposed不是在Flatter_web中更新HtmlView时的真实异常？

我正在尝试使用HtmlView在我的Flitter_web应用程序中显示谷歌地图，但无法在标记更改时可靠地更新地图。它有一半的时间运作良好。请看下面的代码。我订阅InitState（）中的标记更改。当标记器数据更新并侦听返回时，我获得_state！=_PlatformViewState.disposed异常每隔一次，它每隔一次工作

查看Flatter_web平台视图代码，似乎每次使用不同的视图类型创建新的HtmlView时，都会处理以前的HtmlView。重画逻辑似乎有问题，因为此异常在处理视图之后立即发生。此异常后的生成调用成功呈现HtmlView

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building HtmlView(dependencies: [Directionality], state:
_HtmlViewState#705f2):
Assertion failed: org-dartlang-app:///packages/flutter_web/src/services/platform_views.dart:789:12
_state != _PlatformViewState.disposed
is not true

Either the assertion indicates an error in the framework itself, or we should provide substantially
more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new?template=BUG.md

When the exception was thrown, this was the stack:
dart:sdk_internal 4543:15                                        assertFailed
removeOnPlatformViewCreatedListener
package:flutter_web/…/services/platform_views.dart:789
package:flutter_web/src%5Crendering%5Cplatform_view.dart 471:21  set viewController
updateRenderObject (package:flutter_web/src%5Cwidgets%5Cplatform_view.dart:752:17)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4670:12)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4055:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:5069:14)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:3953:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
updateChildren (package:flutter_web/src%5Cwidgets%5Cframework.dart:4769:32)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:5186:17)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4164:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4164:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
updateChildren (package:flutter_web/src%5Cwidgets%5Cframework.dart:4769:32)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:5186:17)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4055:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4164:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4055:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:5069:14)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:3953:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:5069:14)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4164:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
update (package:flutter_web/src%5Cwidgets%5Cframework.dart:4055:5)
updateChild (package:flutter_web/src%5Cwidgets%5Cframework.dart:2896:14)
performRebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3908:16)
rebuild (package:flutter_web/src%5Cwidgets%5Cframework.dart:3713:5)
buildScope (package:flutter_web/src%5Cwidgets%5Cframework.dart:2347:31)
drawFrame (package:flutter_web/src%5Cwidgets%5Cbinding.dart:710:49)
[_handlePersistentFrameCallback] (package:flutter_web/src%5Crendering%5Cbinding.dart:286:5)
[_invokeFrameCallback]
package:flutter_web/…/scheduler/binding.dart:1030
handleDrawFrame
package:flutter_web/…/scheduler/binding.dart:963
[_handleDrawFrame]
package:flutter_web/…/scheduler/binding.dart:874
<fn> (package:flutter_web_ui/src%5Cengine.dart:164:21)
════════════════════════════════════════════════════════════════════════════════════════════════════

══╡ WIDGETS库捕获到异常╞═══════════════════════════════════════════════════════════
在生成HtmlView（依赖项：[方向性]，状态]时引发了以下断言：
_HtmlViewState#705f2）：
断言失败：org dartlang-app:///packages/flutter_web/src/services/platform_views.dart:789:12
_国家！=_PlatformViewState.com
事实并非如此
要么断言表明框架本身存在错误，要么我们应该提供
此错误消息中的更多信息可帮助您确定并修复根本原因。
在任何一种情况下，请通过在GitHub上提交bug来报告此断言：
https://github.com/flutter/flutter/issues/new?template=BUG.md
引发异常时，这是堆栈：
dart:sdk_内部4543:15资产失败
removeOnPlatformViewCreatedListener
软件包：flatter\u web/../services/platform\u views.dart:789
软件包：颤振web/src%5Crendering%5Cplatform\u视图。dart 471:21设置视图控制器
updateRenderObject（包：flatter_web/src%5Cwidgets%5Cplatform_视图。dart:752:17）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4670:12）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4055:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:5069:14）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:3953:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
updateChildren（包：flatter_web/src%5Cwidgets%5Cframework.dart:4769:32）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:5186:17）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4164:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4164:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
updateChildren（包：flatter_web/src%5Cwidgets%5Cframework.dart:4769:32）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:5186:17）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4055:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4164:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4055:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:5069:14）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:3953:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:5069:14）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4164:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
重建（包：flatter_web/src%5Cwidgets%5Cframework.dart:3713:5）
更新（包：flatter_web/src%5Cwidgets%5Cframework.dart:4055:5）
updateChild（包：flatter_web/src%5Cwidgets%5Cframework.dart:2896:14）
performRebuild（包：flatter\u web/src%5Cwidgets%5Cframework.dart:3908:16）
热拜
class Panics extends StatefulWidget {
  final bool selectOnly;
  final bool showAddButton;
  final bool boListGrid;
  final bool boShowAppBar;

  Panics(this.selectOnly,
      [this.showAddButton = true,
      this.boListGrid = true,
      this.boShowAppBar = true]);


  @override
  _PanicsState createState() =>
      _PanicsState(selectOnly, showAddButton, boListGrid, boShowAppBar);
}

class _PanicsState extends State<Panics> {
  final bool selectOnly;
  final bool showAddButton;
  final bool boListGrid;
  final bool boShowAppBar;
  String createdViewId = 'hello-world-html';
  String strMap;
  bool inProgress = true;
  // Subscription
  StreamSubscription subscription;
  List<fs.DocumentSnapshot> panics;

  Map<String, bool> boShowGrid;
  List<fs.DocumentReference> isSelected;
  final key = GlobalKey<ScaffoldState>();

  // final _foldingCellKey = GlobalKey<SimpleFoldingCellState>();

  _PanicsState(
      this.selectOnly, this.showAddButton, this.boListGrid, this.boShowAppBar);



@override
  void initState() {
    debugPrint("PANICS: initState");
    // TODO: implement initState
    isSelected = List<fs.DocumentReference>();
    boShowGrid = Map<String, bool>();
    showPanics(null);
    fs.Query ref;
        if (Globals.role == Role.Manager) {
      // Make a reference to firestore
      ref = firestore()
          .collection('locations')
          .where("hotelId", "==", Globals.hotelID);
    } else {
      // Make a reference to firestore
      ref = firestore()
          .collection('locations')
          .where("userId", "==", Globals.userId);
    }

    ref = ref.where("status", "==", "new");

      subscription = ref.onSnapshot.listen((data) {
        showPanics(data.docs);
      });
    super.initState();
  }


  void showPanics(List<fs.DocumentSnapshot> panics) {
    String markers = "";
    String latlng = "var myLatLng = {lat: 41.850033, lng: -87.6500523}";
    DateTime max = DateTime.fromMicrosecondsSinceEpoch(0);
    fs.GeoPoint lastPanicPosition;

if (panics != null) {
     panics.forEach((data) {
      Panic panic = Panic.fromSnapshot(data);

      String strIcon = (panic.status == 'new')?"http://maps.google.com/mapfiles/ms/icons/red-dot.png":"http://maps.google.com/mapfiles/ms/icons/green-dot.png";
      String marker =
          "var marker = new google.maps.Marker({position: new google.maps.LatLng(${panic.position.latitude}, ${panic.position.longitude})," 
            + "map: map, icon:"$strIcon", title: '${Globals.globals.getUserName(panic.userId)} needs help!'});\n";
      markers += marker;
      DateTime time = panic.timeStamp;
            if (time.compareTo(max) > 0 ) {
        max = time;
        lastPanicPosition = panic.position;
      }
   });
         latlng = "var myLatLng = {lat: ${lastPanicPosition.latitude}, lng: ${lastPanicPosition.longitude}}";
}

debugPrint("Panics: showPanic markers = $markers");
debugPrint("Panics: showPanic latlng = $latlng");

    String createdViewUpdate = DateTime.now().toString();
    rootBundle.loadString('map.html').then((value) {
    String strMapUpdate = value.replaceAll(new RegExp(r'var myLatLng = {lat: 41.850033, lng: -87.6500523}'), latlng);
      strMapUpdate = strMapUpdate.replaceAll(new RegExp(r'markers'), markers);
      debugPrint ("Panics strMapUpdate =: $strMapUpdate");
      ui.platformViewRegistry.registerViewFactory(
          createdViewId,
          (int viewId) => IFrameElement()
            ..width = (MediaQuery.of(context).size.width - 400).toString()
            ..height = MediaQuery.of(context).size.height.toString()
            ..srcdoc = strMapUpdate
            ..style.border = 'none');
    });
if ((panics != null)&&(mounted)) {
    setState(() {
      inProgress = false;
      this.createdViewId = createdViewUpdate;
      this.panics = panics;
    });
}
  }


  @override
  Widget build(BuildContext context) {
  debugPrint("Panics build");
    return (((Globals.globals == null) || (Globals.documentID == null))
        //Uncomment this to use roomList
        //    ||(Globals.roomList.isEmpty)
        )
        ? Scaffold(body: Text("Loading..."))
        : (selectOnly)
            ? Scaffold(
                key: key,
                appBar: AppBar(title: Text(Globals.hotelName + ":Alerts")),
                body: _buildBody(context),
              )
            : (showAddButton)
                ? Scaffold(
                    floatingActionButton: FloatingActionButton(
                      heroTag: "panic",
                      backgroundColor: Colors.greenAccent,
                      mini: true,
                      child: Icon(Icons.person),
                      onPressed: () => setState(() {
                        _deletePanics(context);
                      }),
                    ),
                    floatingActionButtonLocation:
                        FloatingActionButtonLocation.endFloat,
                    appBar: (boShowAppBar)
                        ? AppBar(
                            title: Text(
                                (boListGrid) ? "Alerts list" : "Alerts grid"))
                        : null,
                    body: Row (
                            children: <Widget>[
                                  Container(
                                      width: MediaQuery.of(context).size.width - 400,
                                      child: HtmlView(
                                      viewType: createdViewId,
                                      onPlatformViewCreated: _onPlatformViewCreated,
                                      )),
                                  Container(
                                      width: 400,
                                      child: _buildBody(context),
                                  )
                            ]
                    )
                  )
                : (boShowAppBar)
                    ? Scaffold(
                        appBar: AppBar(title: Text("Panics")),
                        body: _buildBody(context),
                      )
                    : Scaffold(
                        body: _buildBody(context),
                      );
  }

  @override
  Widget build(BuildContext context) {
    debugPrint("Panics: build: boShowAppBar = $boShowAppBar ");
    //showPanics(null);
    return (((Globals.globals == null) || (Globals.documentID == null))
        //Uncomment this to use roomList
        //    ||(Globals.roomList.isEmpty)
        )
        ? Scaffold(body: Text("Loading..."))
        : (selectOnly)
            ? Scaffold(
                key: key,
                appBar: AppBar(title: Text(Globals.hotelName + ":Alerts")),
                body: _buildBody(context),
              )
            : Scaffold(
                    floatingActionButton: (showAddButton) ? FloatingActionButton(
                      heroTag: "panic",
                      backgroundColor: Colors.greenAccent,
                      mini: true,
                      child: Icon(Icons.delete),
                      tooltip: "Delete selected",
                      onPressed: () => setState(() {
                        _deletePanics(context);
                      }),
                    ):null,
                    floatingActionButtonLocation:
                        FloatingActionButtonLocation.endFloat,
                    appBar: (boShowAppBar)
                        ? AppBar(
                            title: Text(
                                (boListGrid) ? "Alerts list" : "Alerts grid"),
                            actions: <Widget>[
                              FlatButton(
                                  onPressed: () => setState(() {
                                        _deletePanics(context);
                                      }),
                                  child: Text("Delete selected",
                                      style: TextStyle(color: Colors.white))),
                            ],
                          )
                        : null,
                    body: Row(children: <Widget>[
                      Container(
                        width: 400,
                        child: _buildBody(context),
                      ),
                        Container(
                        width: MediaQuery.of(context).size.width - 400,
                        child: FutureBuilder(
                          future: Future.delayed(Duration(seconds: 1)),
                          builder: (c,s) => (s.connectionState == ConnectionState.done)?showMap():Container(),)
                      )
                    ]));
  }
  Widget showMap() {
    debugPrint("PANICS: showMap()");
    showPanics(this.panics);
    return HtmlView(      viewType: createdViewId,
                          onPlatformViewCreated: _onPlatformViewCreated,
                        );
  }