List<HistoricTaskInstance> taskInstanceList = historyService
                        .createHistoricTaskInstanceQuery()
                        .taskAssignee(assignee)
                        .processInstanceId(piId)
                        .finished()
                        .list();
                Set<String> iDo = new HashSet<>();
                taskInstanceList.forEach(s->iDo.add(s.getActivityId()));

s.getActivityId()报错

import org.activiti.engine.history.HistoricTaskInstance;

这个是引用包