Question mark converted to %3F in URI - flutter

Question

I'm working on a project and I'm trying to get information from an API. When I write the link it doesn't detect the character "?" and it substitutes this char for "%3F" so I can't access to the API.
final String _charactersUrl = '/api/character/?page=2';
I get status code 500 from the API:
https://rickandmortyapi.com/api/character/%3Fpage=3
The class that gets information from the API
class Api {
final String _baseUrl = 'rickandmortyapi.com';
final String _charactersUrl = '/api/character/?page=2';
final String _charactersJsonKey = 'results';
final HttpClient _httpClient = HttpClient();
Future<List<Character>> getCharacters() async {
final uri = Uri.https(_baseUrl, _charactersUrl);
final response = await _getJson(uri);
if (response == null || response[_charactersJsonKey] == null) {
print('Api.getCharacters(): Error while retrieving characters');
return null;
}
return _convert(response[_charactersJsonKey]);
}
Future<Map<String, dynamic>> _getJson(Uri uri) async {
try {
final request = await _httpClient.getUrl(uri);
final response = await request.close();
if (response.statusCode != HttpStatus.OK) {
print('Api._getJson($uri) status code is ${response.statusCode}');
return null;
}
final responseBody = await response.transform(utf8.decoder).join();
return json.decode(responseBody);
} on Exception catch (e) {
print('Api._getJson($uri) exception thrown: $e');
return null;
}
}
List<Character> _convert(List charactersJson) {
List<Character> characters = <Character>[];
charactersJson.forEach((character) {
characters.add(Character.fromJson(character));
});
return characters;
}
}
I would be very grateful if someone could help me. Thanks!

Answer 1

The Uri class expects you to use the Uri.https constructor differently.
The third positional parameter is queryParameters, which you should use instead of passing your query parameters to the unencodedPath:
final String _baseUrl = 'rickandmortyapi.com';
final String _charactersPath = '/api/character/';
final Map<String, String> _queryParameters = <String, String>{
'page': '2',
};
Future<List<Character>> getCharacters() async {
final uri = Uri.https(_baseUrl, _charactersPath, _queryParameters);
...