如何删除 List<MyDataModel> 的重复项（Dart/Flutter）

Question

我有一个基于列表构建 UI 的 futurebuilder，它完成了这项工作，但是由于每次导航时都会一次又一次地构建 UI，因此我得到了重复。我的问题是，Dart 中是否有一种先天方法可以从列表中删除重复项？我试过这个StackOverflow question 但是它不起作用。

这是我的自定义模型：

class HomeList {
  Widget navigateScreen;
  String imagePath;
  PatientInfo patientInfo;

  HomeList({
    this.navigateScreen,
    this.imagePath = '',
    this.patientInfo,
  });

  static List<HomeList> homeList = [];
}

这是我从 cloud_firestore 获取数据的 futureBuilder 函数：

  _getPatients() async {
    if (didLoadpatients == 0) {
      print('this is didloadpatients at start of func $didLoadpatients');
      var document = await db
          .collection('users')
          .document(mUser.uid)
          .collection('patients');

      document.getDocuments().then((QuerySnapshot query) async {
        query.documents.forEach((f) {
          uids.add(f.data['uID']);
        });
        didLoadpatients++;
      print('this is didloadpatients at end of func $didLoadpatients');
        for (var i = 0; i < uids.length; i++) {
          var userDocuments = await db.collection('users').document(uids[i]);
          userDocuments.get().then((DocumentSnapshot doc) {
            print(doc.data);
            homeList.add(HomeList(
                imagePath: 'assets/fitness_app/fitness_app.png',
                patientInfo: new PatientInfo.fromFbase(doc.data)));
          });
          print(homeList);
        }
      });
    } else 
    print('I am leaving the get patient function');
  }

  Future<bool> getData() async {
    _getCurrentUser();
    await Future.delayed(const Duration(milliseconds: 1500), () async {
      _getPatients();
    });
    return true;
  }

任何帮助将不胜感激！

Answer 1

要删除重复项，您可以使用 Set Data Structure 而不是 List。

只需使用 Set 而不是 List 来获取唯一值。

Answer 2

在添加之前，您可以从模型中删除元素，这将起作用

    dummymodel.removeWhere((m) => m.id == id);
    dummymodel.add(dummymodel.fromJson(data));

Answer 3

要从数据模型中删除重复项，只需使用 Set（数据结构），

包含重复条目的原始列表：

List<MyDataModel> mList = [MyDataModel(1), MyDataModel(2), MyDataModel(1), MyDataModel(3)];

从您的List<MyDataModel> 中删除重复条目的新列表：

List<MyDataModel> mNewList = list.toSet().toList();

输出： 结果会是这样的

MyDataModel(1)、MyDataModel(2)、MyDataModel(3)

Answer 4

我想出了一个蛮力的解决方案。而不是

_getPatients() async {
    if (didLoadpatients == 0) {
      print('this is didloadpatients at start of func $didLoadpatients');
      var document = await db
          .collection('users')
          .document(mUser.uid)
          .collection('patients');

      document.getDocuments().then((QuerySnapshot query) async {
        query.documents.forEach((f) {
          uids.add(f.data['uID']);
        });
        didLoadpatients++;
      print('this is didloadpatients at end of func $didLoadpatients');
        for (var i = 0; i < uids.length; i++) {
          var userDocuments = await db.collection('users').document(uids[i]);
          userDocuments.get().then((DocumentSnapshot doc) {
            print(doc.data);
            homeList.add(HomeList(
                imagePath: 'assets/fitness_app/fitness_app.png',
                patientInfo: new PatientInfo.fromFbase(doc.data)));
          });
          print(homeList);
        }
      });
    } else 
    print('I am leaving the get patient function');
  }

我已经按照@Jay Mungara 所说的做，并在每次我的 UI 重建时清除我的 Set：

_getPatients() async {
homeList.clear();
    if (didLoadpatients == 0) {
      print('this is didloadpatients at start of func $didLoadpatients');
      var document = await db
          .collection('users')
          .document(mUser.uid)
          .collection('patients');

      document.getDocuments().then((QuerySnapshot query) async {
        query.documents.forEach((f) {
          uids.add(f.data['uID']);
        });
        didLoadpatients++;
      print('this is didloadpatients at end of func $didLoadpatients');
        for (var i = 0; i < uids.length; i++) {
          var userDocuments = await db.collection('users').document(uids[i]);
          userDocuments.get().then((DocumentSnapshot doc) {
            print(doc.data);
            homeList.add(HomeList(
                imagePath: 'assets/fitness_app/fitness_app.png',
                patientInfo: new PatientInfo.fromFbase(doc.data)));
          });
          print(homeList);
        }
      });
    } else 
    print('I am leaving the get patient function');
  }

感谢您的所有回答！

Answer 5

要从自定义对象列表中删除重复元素，您需要在 POJO 类中覆盖 == 和 hashcode 方法，然后在 Set 中添加项目并再次将 set 转换为列表以删除重复对象.以下是工作代码：-

class TrackPointList {
double latitude;
double longitude;
String eventName;
Time timeZone;

TrackPointList({
this.latitude,
this.longitude,
this.eventName,
this.timeZone,

});

@override
bool operator==(other) {
// Dart ensures that operator== isn't called with null
// if(other == null) {
//   return false;
// }
if(other is! TrackPointList) {
  return false;
}
// ignore: test_types_in_equals
return eventName == (other as TrackPointList).eventName;

}

int _hashCode;
@override
int get hashCode {
if(_hashCode == null) {
  _hashCode = eventName.hashCode;
}
return _hashCode;

}

factory TrackPointList.fromJson(Map<String, dynamic> json) => TrackPointList(
latitude: json["latitude"].toDouble(),
longitude: json["longitude"].toDouble(),
eventName: json["eventName"],
timeZone: timeValues.map[json["timeZone"]],

);

Map<String, dynamic> toJson() => {
"latitude": latitude,
"longitude": longitude,
"eventName": eventName,
"timeZone": timeValues.reverse[timeZone],

}; }

上面是 POJO 类。下面是帮助您根据 eventName 数据成员过滤对象的方法。

List<TrackPointList> getFilteredList(List<TrackPointList> list){

final existing = Set<TrackPointList>();
final unique = list
    .where((trackingPoint) => existing.add(trackingPoint))
    .toList();

return unique;

}

这肯定会奏效。 如果对您有帮助，请+1。