getGroupWithId method
根据群组id获取群实例
Implementation
Future<EMGroup> getGroupWithId(String groupId) async {
Map req = {'groupId': groupId};
Map result = await _channel.invokeMethod(EMSDKMethod.getGroupWithId, req);
EMError.hasErrorFromResult(result);
return EMGroup.fromJson(result[EMSDKMethod.getGroupWithId]);
}