How to create a custom exception and handle it in dart

You can look at the Exception part of A Tour of the Dart Language.

The following code works as expected (custom exception has been obtained is displayed in console) :

class CustomException implements Exception {
  String cause;
  CustomException(this.cause);
}

void main() {
  try {
    throwException();
  } on CustomException {
    print("custom exception has been obtained");
  }
}

throwException() {
  throw new CustomException('This is my first custom exception');
}