旧

~~~~

final uploadTask = imageStore.putFile(imageFile);
final url = (await uploadTask.future).downloadUrl;

更新

这个答案现在是准确的答案。

final ref = FirebaseStorage.instance
    .ref()
    .child('path')
    .child('to')
    .child('the')
    .child('image_filejpg');

ref.putFile(imageFile);
// or ref.putData(Uint8List.fromList(imageData));

var url = await ref.getDownloadURL() as String;

要么

var url = Uri.parse(await ref.getDownloadURL() as String);