I am building a profile page for a flutter app where a user uploads an image from their gallery and it gets uploaded to FirebaseStorage. I am facing a problem where I'm getting a CastError that's based on using the null check operator on a null value. The variable in question is imageFile but I already did a check using an If statement but I'm getting that error.

Here's my code:

  String name = '';
  String email = '';
  String? image = '';
  File? imageFile;
  String? imageUrl;
  String? userNameInput = '';

  //Upload image to Firebase
  Future<String?> _uploadImageToFirebase() async {
    if (imageFile == null) {
      Fluttertoast.showToast(msg: 'Please upload an image');
    }
**//This is where I'm getting the CastError**
    String fileName = Path.basename(imageFile!.path);

    var reference =
        FirebaseStorage.instance.ref().child('profileImages/$fileName');
    UploadTask uploadTask = reference.putFile(imageFile!);
    TaskSnapshot taskSnapshot = await uploadTask.whenComplete(() => null);
    await taskSnapshot.ref.getDownloadURL().then((value) {
      imageUrl = value;
    }).catchError((e) {
      Fluttertoast.showToast(msg: e.toString());
    });

    FirebaseFirestore.instance
        .collection('users')
        .doc(FirebaseAuth.instance.currentUser!.uid)
        .set({'userImage': imageUrl});
    return imageUrl;
  }

CodePudding user response：

Even though you check you still continue the function after it. You need to return the function if you want it to stop there, so like

if (imageFile == null) {
  Fluttertoast.showToast(msg: 'Please upload an image');
  return null;
}

for example

CodePudding user response：

You are checking, but the control is flowing further so either return or use inline if condition before imageFile!.path

Solution 1 :

 String fileName = imageFile!=null ? Path.basename(imageFile!.path):'';

Solution 2:

if (imageFile == null) {
  Fluttertoast.showToast(msg: 'Please upload an image');
  return null;