unlock method
Unlock an achievement.
Achievement takes three parameters:
androidID the achievement id for android.
iOSID the achievement id for iOS.
percentComplete the completion percent of the achievement, this parameter is
optional in case of iOS.
Implementation
@override
Future<String?> unlock({required Achievement achievement}) async {
return await _channel.invokeMethod("unlock", {
"achievementID": achievement.id,
"percentComplete": achievement.percentComplete,
});
}