Flutter 搜索结果有多个副本

我设计了一个搜索屏幕，在其中搜索学生。下面是一些代码：

 onChanged: (String query) async {
                      _adminAttendance.searchListOfStudents.clear();
                      query = query.trim();
                      if (query.length == 0) {
                        _adminAttendance.loading.value = false;
                        _adminAttendance.isSearched.value = true;
                        _adminAttendance.searchListOfStudents.clear();
                        return;
                      }
                      _adminAttendance.isSearched.value = false;
                      if (query.length >= 3) {
                        _adminAttendance.searchListOfStudents.clear();
                        print(
                            "list cleared ${_adminAttendance.searchListOfStudents.length} : $query");
                        _adminAttendance.loading.value = true;
                        await _adminAttendance.searchStudentsForLecture(
                            liveId: widget.liveId, searchString: query);
                      }
                    },
                    onSubmitted: (String query) {
                      query = query.trim();
                      if (query.length == 0) {
                        _adminAttendance.loading.value = false;
                        _adminAttendance.isSearched.value = true;
                        return;
                      } else {
                        _adminAttendance.isSearched.value = false;
                        _adminAttendance.searchListOfStudents.clear();
                        _adminAttendance.loading.value = true;
                        _adminAttendance.searchStudentsForLecture(
                            liveId: widget.liveId, searchString: query);
                      }
                    },

这就是我在搜索文本字段中所做的

即使我添加了

\u administration.searchListOfStudents.clear（），当文本不断更改时，问题也会出现它显示单个元素的多个副本。
... 提前谢谢