Flutter emulator上的应用程序运行完美，但在真实设备上运行时，位置标记不可见，并且在运行代码时显示无法加载资源

因为问题是emulator中的一切工作正常……即使资源在emulator中成功加载，堆栈仍显示无法加载资源，而且在emulator上成功测试应用程序后，当我在真实设备上运行应用程序时，位置标记不可见，而在emulator中可见

    //This is my code 

import 'package:flutter_polyline_points/flutter_polyline_points.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';
import 'package:flutter/material.dart';
import 'dart:async';
import 'components/map_pin_pill.dart';
import 'Model/pin_pill_info.dart';

const double CAMERA_ZOOM = 16;
const double CAMERA_TILT = 80;
const double CAMERA_BEARING = 30;
const LatLng SOURCE_LOCATION = LatLng(28.357932, 77.167889);
const LatLng DEST_LOCATION = LatLng(28.354017, 77.1605916);

void main() =>
    runApp(MaterialApp(debugShowCheckedModeBanner: false, home: MapPage()));

class MapPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => MapPageState();
}

class MapPageState extends State<MapPage> {
  Completer<GoogleMapController> _controller = Completer();
  Set<Marker> _markers = Set<Marker>();
// for my drawn routes on the map
  Set<Polyline> _polylines = Set<Polyline>();
  List<LatLng> polylineCoordinates = [];
  PolylinePoints polylinePoints= PolylinePoints();
  String googleAPIKey = '';
// for my custom marker pins
  BitmapDescriptor sourceIcon;
  BitmapDescriptor destinationIcon;
// the user's initial location and current location
// as it moves
  LocationData currentLocation;
// a reference to the destination location
  LocationData destinationLocation;
// wrapper around the location API
  Location location;
  double pinPillPosition = -100;
  PinInformation currentlySelectedPin = PinInformation(
      pinPath: '',
      avatarPath: '',
      location: LatLng(0, 0),
      locationName: '',
      labelColor: Colors.grey);
  PinInformation sourcePinInfo;
  PinInformation destinationPinInfo;

  @override
  void initState() {
    super.initState();

    // create an instance of Location
    location = new Location();
    polylinePoints = PolylinePoints();

    // subscribe to changes in the user's location
    // by "listening" to the location's onLocationChanged event
    location.onLocationChanged.listen((LocationData cLoc) {
      // cLoc contains the lat and long of the
      // current user's position in real time,
      // so we're holding on to it
      currentLocation = cLoc;
      updatePinOnMap();
    });
    // set custom marker pins
    setSourceAndDestinationIcons();
    // set the initial location
    setInitialLocation();
  }

  void setSourceAndDestinationIcons() async {
    BitmapDescriptor.fromAssetImage(
        ImageConfiguration(devicePixelRatio: 2.0), 'assets/driving_pin.png')
        .then((onValue) {
      sourceIcon = onValue;
    });

    BitmapDescriptor.fromAssetImage(ImageConfiguration(devicePixelRatio: 2.0),
        'assets/destination_map_marker.png')
        .then((onValue) {
      destinationIcon = onValue;
    });
  }

  void setInitialLocation() async {
    // set the initial location by pulling the user's
    // current location from the location's getLocation()
    currentLocation = await location.getLocation();

    // hard-coded destination for this example
    destinationLocation = LocationData.fromMap({
      "latitude": DEST_LOCATION.latitude,
      "longitude": DEST_LOCATION.longitude
    });
  }

  @override
  Widget build(BuildContext context) {
    CameraPosition initialCameraPosition = CameraPosition(
        zoom: CAMERA_ZOOM,
        tilt: CAMERA_TILT,
        bearing: CAMERA_BEARING,
        target: SOURCE_LOCATION);
    if (currentLocation != null) {
      initialCameraPosition = CameraPosition(
          target: LatLng(currentLocation.latitude, currentLocation.longitude),
          zoom: CAMERA_ZOOM,
          tilt: CAMERA_TILT,
          bearing: CAMERA_BEARING);
    }
    return Scaffold(
      body: Stack(
        children: <Widget>[
          GoogleMap(
              myLocationEnabled: true,
              compassEnabled: true,
              tiltGesturesEnabled: false,
              markers: _markers,
              polylines: _polylines,
              mapType: MapType.normal,
              initialCameraPosition: initialCameraPosition,
              onTap: (LatLng loc) {
                pinPillPosition = -100;
              },
              onMapCreated: (GoogleMapController controller) {//dikkat
               // controller.setMapStyle(Utils.mapStyles);
                _controller.complete(controller);
                // my map has completed being created;
                // i'm ready to show the pins on the map
                showPinsOnMap();
              }),
          MapPinPillComponent(
              pinPillPosition: pinPillPosition,
              currentlySelectedPin: currentlySelectedPin),
          Positioned(
              bottom: 90,
              right: 10,
              child:
              FlatButton(
                  child: Icon(Icons.pin_drop, color: Colors.white),
                  color: Colors.green,
                  onPressed: updatePinOnMap
              )
          ),
        ],
      ),
    );
  }

  void showPinsOnMap() {
    // get a LatLng for the source location
    // from the LocationData currentLocation object
    var pinPosition =
    LatLng(currentLocation.latitude, currentLocation.longitude);
    // get a LatLng out of the LocationData object
    var destPosition =
    LatLng(destinationLocation.latitude, destinationLocation.longitude);

    sourcePinInfo = PinInformation(
        locationName: "Start Location",
        location: SOURCE_LOCATION,
        pinPath: "assets/driving_pin.png",
        avatarPath: "assets/friend1.jpg",
        labelColor: Colors.blueAccent);

    destinationPinInfo = PinInformation(
        locationName: "End Location",
        location: DEST_LOCATION,
        pinPath: "assets/destination_map_marker.png",
        avatarPath: "assets/friend2.jpg",
        labelColor: Colors.purple);

    // add the initial source location pin
    _markers.add(Marker(
        markerId: MarkerId('sourcePin'),
        position: pinPosition,
        onTap: () {
          setState(() {
            currentlySelectedPin = sourcePinInfo;
            pinPillPosition = 0;
          });
        },
        icon: sourceIcon));
    // destination pin
    _markers.add(Marker(
        markerId: MarkerId('destPin'),
        position: destPosition,
        onTap: () {
          setState(() {
            currentlySelectedPin = destinationPinInfo;
            pinPillPosition = 0;
          });
        },
        icon: destinationIcon));
    // set the route lines on the map from source to destination
    // for more info follow this tutorial
    setPolylines();
  }

  void setPolylines() async {
    PolylineResult result = await polylinePoints.getRouteBetweenCoordinates(googleAPIKey,
        PointLatLng(currentLocation.latitude, currentLocation.longitude),
      PointLatLng(destinationLocation.latitude,destinationLocation.longitude));

    if(result.points.isNotEmpty) {
      print("not empty");
      result.points.forEach((PointLatLng point) {
        polylineCoordinates.add(LatLng(point.latitude, point.longitude));
      });

      setState(() {
        _polylines.add(Polyline(
            width: 3, // set the width of the polylines
            polylineId: PolylineId("poly"),
            color: Color.fromARGB(255, 40, 122, 198),
            points: polylineCoordinates));
      });
    }
  }

  void updatePinOnMap() async {
    // create a new CameraPosition instance
    // every time the location changes, so the camera
    // follows the pin as it moves with an animation
    CameraPosition cPosition = CameraPosition(
      zoom: CAMERA_ZOOM,
      tilt: CAMERA_TILT,
      bearing: CAMERA_BEARING,
      target: LatLng(currentLocation.latitude, currentLocation.longitude),
    );
    final GoogleMapController controller = await _controller.future;
    controller.animateCamera(CameraUpdate.newCameraPosition(cPosition));
    // do this inside the setState() so Flutter gets notified
    // that a widget update is due
    setState(() {
      // updated position
      var pinPosition =
      LatLng(currentLocation.latitude, currentLocation.longitude);

      sourcePinInfo.location = pinPosition;

      // the trick is to remove the marker (by id)
      // and add it again at the updated location
      _markers.removeWhere((m) => m.markerId.value == 'sourcePin');
      _markers.add(Marker(
          markerId: MarkerId('sourcePin'),
          onTap: () {
            setState(() {
              currentlySelectedPin = sourcePinInfo;
              pinPillPosition = 0;
            });
          },
          position: pinPosition, // updated position
          icon: sourceIcon));
    });
  }
}
 

//这是我的代码
导入“包：颤振多段线点/颤振多段线点.省道”；
导入“包：google_-maps_-flatter/google_-maps_-flatter.dart”；
导入“package:location/location.dart”；
进口“包装：颤振/材料.省道”；
导入“dart:async”；
导入“组件/map_pin_pill.dart”；
导入'Model/pin_pill_info.dart'；
const双摄像机_变焦=16；
const双摄像头倾斜=80；
常数双摄像机_轴承=30；
const LatLng SOURCE_LOCATION=LatLng（28.357932,77.167889）；
const-LatLng DEST_位置=LatLng（28.354017,77.1605916）；
void main（）=>
runApp（MaterialApp（debugShowCheckedModeBanner:false，home:MapPage（））；
类MapPage扩展StatefulWidget{
@凌驾
State createState（）=>MapPageState（）；
}
类MapPageState扩展了状态{
Completer _controller=Completer（）；
Set _markers=Set（）；
//我在地图上画的路线
Set _polylines=Set（）；
列出多段线坐标=[]；
多段线点多段线点=多段线点（）；
字符串googleAPIKey=''；
//为我的自定义标记别针
位图描述符源图标；
位映射描述符定义；
//用户的初始位置和当前位置
//当它移动时
位置数据当前位置；
//对目标位置的引用
位置数据目的地位置；
//位置API的包装器
位置；
双针孔位置=-100；
PinInformation currentlySelectedPin=PinInformation(
pinPath:“”，
化身路径：“”，
位置：LatLng（0,0），
位置名称：“”，
标签颜色：颜色。灰色）；
pininfo信息源pininfo；
PinInformation destinationPinInfo；
@凌驾
void initState（）{
super.initState（）；
//创建位置的实例
位置=新位置（）；
多段线点=多段线点（）；
//订阅用户位置的更改
//通过“侦听”位置的onLocationChanged事件
location.onLocationChanged.listen（（LocationData cLoc）{
//cLoc包含对象的lat和long
//实时显示当前用户的位置，
//所以我们坚持住了
currentLocation=cLoc；
updateMap（）；
});
//设置自定义标记销
设置来源和目的（）；
//设置初始位置
setInitialLocation（）；
}
void setSourceAndDestinations（）异步{
BitmapDescriptor.fromAssetImage(
ImageConfiguration（devicePixelRatio:2.0），“资产/驱动_pin.png”）
.然后（（onValue）{
sourceIcon=onValue；
});
BitmapDescriptor.fromAssetImage（图像配置（devicePixelRatio:2.0），
“assets/destination\u map\u marker.png”）
.然后（（onValue）{
目的地=价值；
});
}
void setInitialLocation（）异步{
//通过拉动用户的鼠标来设置初始位置
//来自位置的getLocation（）的当前位置
currentLocation=等待位置。getLocation（）；
//本例中的硬编码目的地
destinationLocation=LocationData.fromMap({
“纬度”：目的地位置。纬度，
“经度”：DEST_LOCATION.longitude
});
}
@凌驾
小部件构建（构建上下文）{
CameraPosition initialCameraPosition=CameraPosition(
变焦：相机变焦，
倾斜：摄像机倾斜，
轴承：摄像机轴承，
目标：源位置）；
if（currentLocation！=null）{
initialCameraPosition=CameraPosition(
目标：LatLng（currentLocation.latitude，currentLocation.longitude），
变焦：相机变焦，
倾斜：摄像机倾斜，
轴承：摄像机轴承）；
}
返回脚手架(
主体：堆栈(
儿童：[
谷歌地图(
myLocationEnabled:对，
同谋：是的，
tiltGesturesEnabled:false，
标记：_标记，
多段线：_多段线，
mapType:mapType.normal，
initialCameraPosition:initialCameraPosition，
onTap：（LatLng loc）{
pinPillPosition=-100；
},
onMapCreated:（谷歌地图控制器）{//dikkat
//controller.setMapStyle（Utils.mapStyles）；
_控制器。完成（控制器）；
//我的地图已经完成创建；
//我已经准备好在地图上显示图钉了
showPinsOnMap（）；
}),
MapPinpill组件(
pinPillPosition:pinPillPosition，
currentlySelectedPin:currentlySelectedPin），
定位(
底部：90，
右:10,，
儿童：
扁平按钮(
子：图标（Icons.pin_drop，颜色：Colors.white），
颜色：颜色。绿色，
onPressed:UpdateMap
)
),
],
),
);
}
void showPinsOnMap（）{
//获取源位置的LatLng
//从LocationData currentLocation对象
var精确定位=
LatLng（当前位置.纬度，当前位置.经度）；
//从LocationData对象中获取一个LatLng
无功位移=
LatLng（目的地位置.纬度，目的地位置.经度）；
sourcePinInfo=PinInformation(
locationName：“开始位置”，
位置：源位置，
pinPath:“资产/driving_pin.png”，
头像路径：“资产/友谊1.jpg”，
标签颜色：颜色。蓝色调）；
destinationPinInfo=PinInformation(
locationName:“结束位置”，
Syncing files to device Android SDK built for x86...
D/EGL_emulation( 9741): eglMakeCurrent: 0xa6584ea0: ver 2 0 (tinfo 0x90713ec0)
E/BufferQueueProducer( 9741): [SurfaceTexture-0-9741-1] setAsyncMode: BufferQueue has been abandoned
E/BufferQueueProducer( 9741): [SurfaceTexture-0-9741-1] cancelBuffer: BufferQueue has been abandoned
Restarted application in 3,158ms.
W/DynamiteModule( 9741): Local module descriptor class for providerinstaller not found.
I/DynamiteModule( 9741): Considering local module providerinstaller:0 and remote module providerinstaller:0
W/ProviderInstaller( 9741): Failed to load providerinstaller module: No acceptable module found. Local version is 0 and remote version is 0.
W/ConnectivityManager.CallbackHandler( 9741): callback not found for CALLBACK_CAP_CHANGED message
W/ConnectivityManager.CallbackHandler( 9741): callback not found for CALLBACK_IP_CHANGED message
W/DynamiteModule( 9741): Local module descriptor class for providerinstaller not found.
I/DynamiteModule( 9741): Considering local module providerinstaller:0 and remote module providerinstaller:0
W/ProviderInstaller( 9741): Failed to load providerinstaller module: No acceptable module found. Local version is 0 and remote version is 0.
W/ConnectivityManager.CallbackHandler( 9741): callback not found for CALLBACK_IP_CHANGED message
I/Google Maps Android API( 9741): Google Play services package version: 203019022
D/        ( 9741): HostConnection::get() New Host Connection established 0x872a9500, tid 10180
D/EGL_emulation( 9741): eglCreateContext: 0x8f55fda0: maj 1 min 0 rcv 1
D/EGL_emulation( 9741): eglMakeCurrent: 0xa6584ea0: ver 2 0 (tinfo 0x90713ec0)
I/flutter ( 9741): GOOGLE MAPS URL: https://maps.googleapis.com/maps/api/directions/json?origin=28.3524217%2C77.3368383&destination=28.354017%2C77.16059159999998&mode=driving&avoidHighways=false&avoidFerries=true&avoidTolls=false&key=API_KEY
D/EGL_emulation( 9741): eglMakeCurrent: 0x8f55fda0: ver 1 0 (tinfo 0x8f4360f0)

══╡ EXCEPTION CAUGHT BY IMAGE RESOURCE SERVICE ╞════════════════════════════════════════════════════
The following assertion was thrown resolving an image codec:
Unable to load asset:

When the exception was thrown, this was the stack:
#0      PlatformAssetBundle.load (package:flutter/src/services/asset_bundle.dart:223:7)
<asynchronous suspension>
#1      AssetBundleImageProvider._loadAsync (package:flutter/src/painting/image_provider.dart:669:31)
#2      AssetBundleImageProvider.load (package:flutter/src/painting/image_provider.dart:652:14)
#3      ImageProvider.resolveStreamForKey.<anonymous closure> (package:flutter/src/painting/image_provider.dart:505:13)
#4      ImageCache.putIfAbsent (package:flutter/src/painting/image_cache.dart:360:22)
#5      ImageProvider.resolveStreamForKey (package:flutter/src/painting/image_provider.dart:503:80)
#6      ScrollAwareImageProvider.resolveStreamForKey (package:flutter/src/widgets/scroll_aware_image_provider.dart:108:19)
#7      ImageProvider.resolve.<anonymous closure> (package:flutter/src/painting/image_provider.dart:334:9)
#8      ImageProvider._createErrorHandlerAndKey.<anonymous closure>.<anonymous closure> (package:flutter/src/painting/image_provider.dart:464:26)
(elided 13 frames from dart:async)

Image provider: AssetImage(bundle: null, name: "")
Image key: AssetBundleImageKey(bundle: PlatformAssetBundle#b540c(), name: "", scale: 1.0)
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by image resource service ════════════════════════════════════════════════
The following assertion was thrown resolving an image codec:
Unable to load asset: 

When the exception was thrown, this was the stack: 
#0      PlatformAssetBundle.load (package:flutter/src/services/asset_bundle.dart:223:7)
<asynchronous suspension>
#1      AssetBundleImageProvider._loadAsync (package:flutter/src/painting/image_provider.dart:669:31)
#2      AssetBundleImageProvider.load (package:flutter/src/painting/image_provider.dart:652:14)
#3      ImageProvider.resolveStreamForKey.<anonymous closure> (package:flutter/src/painting/image_provider.dart:505:13)
...
Image provider: AssetImage(bundle: null, name: "")
Image key: AssetBundleImageKey(bundle: PlatformAssetBundle#b540c(), name: "", scale: 1.0)
════════════════════════════════════════════════════════════════════════════════════════════════════
I/zygote  ( 9741): NativeAlloc concurrent copying GC freed 49007(2MB) AllocSpace objects, 12(720KB) LOS objects, 40% free, 8MB/14MB, paused 587us total 174.752ms
I/zygote  ( 9741): NativeAlloc concurrent copying GC freed 18774(778KB) AllocSpace objects, 0(0B) LOS objects, 42% free, 8MB/14MB, paused 1.075ms total 187.684ms
I/zygote  ( 9741): NativeAlloc concurrent copying GC freed 4679(318KB) AllocSpace objects, 0(0B) LOS objects, 42% free, 8MB/14MB, paused 22.482ms total 146.268ms
D/        ( 9741): HostConnection::get() New Host Connection established 0xa3bc5200, tid 9963
D/        ( 9741): HostConnection::get() New Host Connection established 0xa3bc5d40, tid 10271
D/        ( 9741): HostConnection::get() New Host Connection established 0x77dfe380, tid 10294