Flutter '；包装：颤振/src/painting/_network_image_io.dart'；：断言失败：第22行第14位：'；网址！=空'；：事实并非如此

帮帮我，图像显示来自URL，但终端显示该URL！=null不是真的 ════════ widgets库捕获到异常═══════════════════════════════════════════════════════ 生成ProfileScreen时抛出了以下断言（脏，状态：_ProfileScreenState#29296）：

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'package:flatter/src/painting/_network\u image\u io.dart'：失败的断言：第22行位置14:'url！=null'：不正确。

您从SharedReferences获取图像url了吗？`U loadSellerPictureUrl（）异步{SharedReferences prefs=await SharedReferences.getInstance（）；setState（（）{sellerPicture=（prefs.getString（'sellerPicture'）？？“”）；return sellerPicture；}`您能更新当前的问题吗？

class CustomCircleAvatar extends StatefulWidget {
final Image myImage;

final String initials;

CustomCircleAvatar({this.myImage, this.initials});

@override
_CustomCircleAvatarState createState() => new _CustomCircleAvatarState();
}

class _CustomCircleAvatarState extends State {
bool _checkLoading = true;

@override
void initState() {
super.initState();
widget.myImage.image.resolve(new ImageConfiguration()).addListener(
ImageStreamListener((ImageInfo info, bool synchronousCall) {
if (mounted) {
setState(() {
_checkLoading = false;
});
}
}));
}

@override
Widget build(BuildContext context) {
return _checkLoading == true
? new CircleAvatar(
child: new Text(
widget.initials,
style: TextStyle(fontSize: 60),
))
: new CircleAvatar(
backgroundImage: widget.myImage.image,
);
}
}

Positioned _profilePhoto(BuildContext context) {
return Positioned(
bottom: -70,
child: Container(
width: 150.0,
height: 150.0,
padding: EdgeInsets.all(3.0),
decoration: BoxDecoration(color: Colors.white, shape: BoxShape.circle),
child: CustomCircleAvatar(
myImage: Image.network(sellerPicture), // This sellerPicture i got from sharedPreferences
initials: '$sellerName'.substring(0, 1).toUpperCase(),
),
),
);
}