I upload an image to firebase storage but i can't see image in firebase storage

First this is about my uploadImage code, I try to fix it again and again but doesn’t work

Future uploadImageFile() async
  {
    String fileName = DateTime.now().millisecondsSinceEpoch.toString();
    StorageReference storageReference = FirebaseStorage.instance.ref().child("Chat Images").child(fileName);

    StorageUploadTask storageUploadTask = storageReference.putFile(imageFile);
    StorageTaskSnapshot storageTaskSnapshot = await storageUploadTask.onComplete;

    storageTaskSnapshot.ref.getDownloadURL().then((downloadUrl){
      
      imageUrl = downloadUrl;
      setState(() {
        isLoading = false;
        onSendMessage(imageUrl, 1);
      });
    }, onError: (error){
      setState(() {
        isLoading = false;
      });
      Fluttertoast.showToast(msg: "Error: " + error);
    });
  }

And after in click upload image the result in terminal like this :

[VERBOSE-2:ui_dart_state.cc(209)] Unhandled Exception: type 'PlatformException' is not a subtype of type 'String'
#0      ChatScreenState.uploadImageFile.<anonymous closure> (package:telegramchatapp/Pages/ChattingPage.dart:726:47)
#1      _rootRunUnary (dart:async/zone.dart:1436:47)
#2      _CustomZone.runUnary (dart:async/zone.dart:1335:19)
#3      _FutureListener.handleError (dart:async/future_impl.dart:178:22)
#4      Future._propagateToListeners.handleError (dart:async/future_impl.dart:779:47)
#5      Future._propagateToListeners (dart:async/future_impl.dart:800:13)
#6      Future._completeError (dart:async/future_impl.dart:610:5)
#7      _completeOnAsyncError (dart:async-patch/async_patch.dart:276:13)
#8      StorageReference.getDownloadURL (package:firebase_storage/src/storage_reference.dart)
<asynchronous suspension>
      

I don’t know what to do.

>Solution :

The exception you show in your question comes from this line:

Fluttertoast.showToast(msg: "Error: " + error);

The error in here is not a string, so you can’t concatenate it to a string. What you want is:

Fluttertoast.showToast(msg: "Error: " + error.toString());

Or:

Fluttertoast.showToast(msg: "Error: $error");

That will then show you what the root cause of the upload failure is, so you can address that.