How to handle this exceptions in flutter? - exception

Question

as I am new to the flutter, I came across the following exception while making a test app with the HTTP module and can't seem to find a solution around. Can anyone suggest a solution?
Future addProduct(Product product) {
const url = 'wrong_url_that_throws_format_error';
return http
.post(
url,
body: json.encode({
'title': product.title,
'description': product.description,
'imageUrl': product.imageUrl,
'price': product.price,
'isFavorite': product.isFavorite,
}),
).then((response) {
// Do things if successful
}).catchError((error) {
throw error;
});
}
// And in the widget
addProduct(_editedProduct).catchError((_) {
// this return will throw exception saying:
// Unhandled Exception: type 'Future<dynamic>' is not a subtype of type 'FutureOr<Null>'
return showDialog(
context: context,
builder: (ctx) => AlertDialog(
title: const Text('Oops'),
content: const Text('Something went wrong.'),
actions: <Widget>[
FlatButton(
child: const Text('Ok'),
onPressed: () {
Navigator.of(ctx).pop();
},
),
],
),
);
}).then((_) {
setState(() {
_isLoading = false;
});
Navigator.of(context).pop();
});

Answer 1

According to the error message, the returned type was Future(dynamic), while the expected returning type was a FutureOr(Null). As the message says, FutureOr<Null> isn't a subtype of Future<dynamic>.
You can fix that by specifying the returning type of showDialog, so it returns the right type. Instead of:
return showDialog(...)
use:
return showDialog<Null>(...)