Question

使用Realm for Android我有一个自定义排序会抛出java.lang.UnsupportedOperationException：不支持替换和元素

所以，我有一段数据需要在我从Realm数据库中检索后进行排序，所以它就像这样坐在List集合中：

Collections.sort(stores, new DistanceComparator(currentLocation));

DistanceComparator如下所示：

public class DistanceComparator implements Comparator<Restaurant> {
    private Location currentLocation;

    public DistanceComparator(Location location) {
        currentLocation = location;
    }

    public int compare(RealmObject c1, RealmObject c2) {
        if ((LocationUtil.calculateSomeValue(c1.getLocation()))
            == (LocationUtil.calculateSomeValue(c2.getLocation()))) {
            return 0;
        }
        else if ((LocationUtil.calculateSomeValue(c1.getLocation()))
            < (LocationUtil.calculateSomeValue(c2.getLocation()))) {
            return -1;
        }
        else {
            return 1;
        }
    }
}

然而，当我执行排序时，我得到了一个：

java.lang.UnsupportedOperationException: Replacing and element is not supported.                                                                              
    at io.realm.RealmResults$RealmResultsListIterator.set(RealmResults.java:868)
    at io.realm.RealmResults$RealmResultsListIterator.set(RealmResults.java:799)
    at java.util.Collections.sort(Collections.java:247)

由于数据的瞬态特性，我无法在Realm中执行排序。

您是否可以对碰巧拥有Realm数据的集合执行基本排序，还是需要在RealmObject类中添加某种注释才能执行此类排序？

我确实看过这个问题，如果这不起作用，那就是我的后备：How do you sort a RealmList or RealmResult by distance?

Answer 1

您无法在RealmResult上执行自定义排序。您必须将结果复制到非托管List并使用它而不是领域结果。

List<ModelMyFlirtsItem> storesList = realm.copyFromRealm(stores);
Collections.sort(storesList, new DistanceComparator(currentLocation));

Answer 2

您可以考虑将LocationUtil评估的值移动到RealmObject本身，并按Realm进行排序。

public int compare(RealmObject c1, RealmObject c2) {
    if ((LocationUtil.calculateSomeValue(c1.getLocation()))
        == (LocationUtil.calculateSomeValue(c2.getLocation()))) {
        return 0;
    }
    else if ((LocationUtil.calculateSomeValue(c1.getLocation()))
        < (LocationUtil.calculateSomeValue(c2.getLocation()))) {
        return -1;
    }
    else {
        return 1;
    }
}

可能是

public class RealmObject extends RealmObject {
    private Integer distance;
    private Location location;

    public void setLocation(Location location) {
        if(location == null) {
            this.distance = null;
        } else {
            this.distance = LocationUtil.calculateSomeValue(location);
        }
        this.location = location;
    }
}

然后

RealmResults<RealmObject> results = realm.where(RealmObject.class).findAllSorted("distance", Sort.ASCENDING);

Answer 3

在RealmResults中使用排序，我也遇到了这个问题。我仅使用Realm的本机.sort()函数解决了该问题。例如-

RealmResult<Location> stores......;
 .......
 .......
 stores.sort(new DistanceComparator(currentLocation));

Realm Custom Sort抛出UnsupportedOperationException

3 个答案: