Java 合并多个RealmList´；对结果列表进行排序？

我刚开始在我当前的android应用程序中使用Realm，到目前为止它非常棒。 不幸的是，我遇到了一个问题：

在我的应用程序中，用户可以将不同类型的条目（他今天吃了什么？喝了什么饮料？）添加到他的日记中。 一个日记条目对象表示给定日期（例如2017年5月21日等）所有条目的总和

我为我的问题想出了一个暂时的解决办法，但它还远远不够完美。 下面的代码是在UI线程上执行的，这显然是错误的做法

List<RealmObject> entryList = new ArrayList<>();
        OrderedRealmCollectionSnapshot<MealEntry> mealEntries = diaryEntry.getMealEntries().createSnapshot();
        OrderedRealmCollectionSnapshot<DrinkEntry> drinkEntries = diaryEntry.getDrinkEntries().createSnapshot();
        OrderedRealmCollectionSnapshot<MedicineEntry> medicineEntries = diaryEntry.getMedicineEntries().createSnapshot();
        OrderedRealmCollectionSnapshot<SymptomEntry> symptomEntries = diaryEntry.getSymptomEntries().createSnapshot();

        entryList.addAll(mealEntries);
        entryList.addAll(drinkEntries);
        entryList.addAll(medicineEntries);
        entryList.addAll(symptomEntries);

        Collections.sort(entryList, entryComparator);

如前所述，所有这些都发生在UI线程上

我知道我不能跨线程传递

RealmObject

s、

RealmList

s和

RealmResult

s，所以我真的很难想出一个异步解决方案。我想启动一个后台线程，并在其中创建

日志条目

对象中所有

RealmList

的副本。然后合并这个非托管列表并对其进行排序——所有这些都在后台线程上进行

所以我的问题是：对于合并多个

RealmList

s并对合并的列表进行排序，是否有任何首选策略？所有这些都是以异步方式进行的？我的上述尝试是否有效？

谢谢@EpicPandaForce

我完全按照您描述的方式解决了它，它就像一个魔咒一样工作-现在我甚至有了实时功能，不需要手动刷新数据，很好：）

如果有人面临同样的问题，我会在这里发布一些代码片段，展示我是如何用代码解决的

public class Entry extends RealmObject {
    private static final int ENTRY_MEAL = 0;
    private static final int ENTRY_DRINK = 1;
    private static final int ENTRY_SYMPTOM = 2;
    private static final int ENTRY_MEDICINE = 3;

    /** The tag describes what kind of entry it represents */
    private int tag;

    /* Only one of these can be set, according to what this entry represents. */
    @Nullable private MealEntry mealEntry;
    @Nullable private DrinkEntry drinkEntry;
    @Nullable private SymptomEntry symptomEntry;
    @Nullable private MedicineEntry medicineEntry;

    /** The time value this entry was created at */
    /** Format: hours + minutes * 60 */
    private int time;

    public int getTime() {
        return time;
    }

/* Can only be accessed from within the 'data' package */

    void setTime(int time) {
        this.time = time;
    }

/**
     * Creates a new entry object in the realm database and tags it as 'MEAL'
     *
     * @param realm not null
     * @param mealEntry the {@link MealEntry} object to map this entry to, not null
     *
     * @return the newly created entry
     */
    static Entry createEntryAsMeal(@NonNull final Realm realm, @NonNull final MealEntry mealEntry) {
        if(realm == null) {
            throw new IllegalArgumentException("'realm' may not be null");
        }
        if(mealEntry == null) {
            throw new IllegalArgumentException("'mealEntry' may not be null");
        }

        Entry entry = realm.createObject(Entry.class);
        entry.tag = ENTRY_MEAL;
        entry.mealEntry = mealEntry;
        return entry;
        }

/* Same methods for other tag types ... */

在MealEntry.class中：

public class MealEntry extends RealmObject {

    @PrimaryKey @Required private String id;

    @Required private String title;

    /** The entry objects this meal-entry is added to */
    Entry entry;

    /** This time value describes when the user consumed this meal **/
    private int time;
// other fields

/**
* Creates a new MealEntry object in the realm.
 * <p>
 *     Note: It is important to use this factory method for creating {@link MealEntry} objects in realm.
 *     Under the hood, a {@link Entry} object is created for every MealEntry and linked to it.
 * </p>
 *
 * @param realm not null
 *
 * @return new MealEntry object which has been added to the <code>realm</code>
 */
public static MealEntry createInRealm(@NonNull Realm realm) {
    if(realm == null) {
        throw new IllegalArgumentException("'realm' may not be null");
    }

    MealEntry mealEntry = realm.createObject(MealEntry.class, UUID.randomUUID().toString());
    mealEntry.entry = Entry.createEntryAsMeal(realm, mealEntry);
    return mealEntry;
}

Entry.class和MealEntry.class中存在“time”字段，因此如果后者发生更改，则必须相应更新条目：

/**
     * Sets the time value for the <code>mealEntry</code> to the specified value.
     * <p>
     *     Note: This method is necessary in order to sync the new time value with the underlying
     *     {@link Entry} object that is connected with the <code>mealEntry</code>.
     * </p>
     *
     * @param mealEntry the {@link MealEntry} object to set the time for, not null
     *
     * @param time the new time value, must be in range of [0, 24*60] because of the format: hours*60 + minutes
     *
     */
    public static void setTimeForMealEntry(@NonNull MealEntry mealEntry, @IntRange(from=0, to=24*60) int time) {
        if(mealEntry == null) {
            throw new IllegalArgumentException("'mealEntry' may not be null");
        }

        mealEntry.setTime(time);

        Entry entry = mealEntry.entry;
        if(entry == null) {
            throw new IllegalStateException("'mealEntry' contains no object of type 'Entry'! Something went wrong on creation of the 'mealEntry'");
        }

        /* Syncs the entries time value with the time value for this MealEntry. */
        /* That´s important for sorting a list of all entries. */
        entry.setTime(time);
    }

注意：我本可以只在测量区内存储相应输入对象的ID，反之亦然。对于输入对象，将ID存储到相应的测量区对象。然而，我不知道这在性能上有什么不同，所以我只采用上述方法。

---

另一种方法的一个原因是，我不必存储“time”字段两次，一次存储在Entry.class中，一次存储在MealEntry.class中，因为在Entry.class中，我可以通过根据其ID查找相应的MealEntry对象来获取时间值，然后获取时间。

您不能对RealmResults进行排序，在您的例子中，我认为您实际上想要的是“单表继承”，并且有一个带有

类型
字段的
条目
类，该字段将是
膳食
，
饮料
，
症状
，
药物
。后台线程非托管+排序也可以工作，但您应该始终确保在这些RealmResults中的一个发生更改时（
RealmChangeListener
）可以执行此过程——尽管这部分已经很棘手，因为对链接所做的更改不会在日记条目上调用RealmChangeListener。非常感谢，这个解决方案看起来绝对更干净，尽管它包含一些数据类的开销。实时数据更新弥补了这一缺陷；）
public class Entry extends RealmObject {
    private static final int ENTRY_MEAL = 0;
    private static final int ENTRY_DRINK = 1;
    private static final int ENTRY_SYMPTOM = 2;
    private static final int ENTRY_MEDICINE = 3;

    /** The tag describes what kind of entry it represents */
    private int tag;

    /* Only one of these can be set, according to what this entry represents. */
    @Nullable private MealEntry mealEntry;
    @Nullable private DrinkEntry drinkEntry;
    @Nullable private SymptomEntry symptomEntry;
    @Nullable private MedicineEntry medicineEntry;

    /** The time value this entry was created at */
    /** Format: hours + minutes * 60 */
    private int time;

    public int getTime() {
        return time;
    }

/* Can only be accessed from within the 'data' package */

    void setTime(int time) {
        this.time = time;
    }

/**
     * Creates a new entry object in the realm database and tags it as 'MEAL'
     *
     * @param realm not null
     * @param mealEntry the {@link MealEntry} object to map this entry to, not null
     *
     * @return the newly created entry
     */
    static Entry createEntryAsMeal(@NonNull final Realm realm, @NonNull final MealEntry mealEntry) {
        if(realm == null) {
            throw new IllegalArgumentException("'realm' may not be null");
        }
        if(mealEntry == null) {
            throw new IllegalArgumentException("'mealEntry' may not be null");
        }

        Entry entry = realm.createObject(Entry.class);
        entry.tag = ENTRY_MEAL;
        entry.mealEntry = mealEntry;
        return entry;
        }

/* Same methods for other tag types ... */

public class MealEntry extends RealmObject {

    @PrimaryKey @Required private String id;

    @Required private String title;

    /** The entry objects this meal-entry is added to */
    Entry entry;

    /** This time value describes when the user consumed this meal **/
    private int time;
// other fields

/**
* Creates a new MealEntry object in the realm.
 * <p>
 *     Note: It is important to use this factory method for creating {@link MealEntry} objects in realm.
 *     Under the hood, a {@link Entry} object is created for every MealEntry and linked to it.
 * </p>
 *
 * @param realm not null
 *
 * @return new MealEntry object which has been added to the <code>realm</code>
 */
public static MealEntry createInRealm(@NonNull Realm realm) {
    if(realm == null) {
        throw new IllegalArgumentException("'realm' may not be null");
    }

    MealEntry mealEntry = realm.createObject(MealEntry.class, UUID.randomUUID().toString());
    mealEntry.entry = Entry.createEntryAsMeal(realm, mealEntry);
    return mealEntry;
}

/**
     * Sets the time value for the <code>mealEntry</code> to the specified value.
     * <p>
     *     Note: This method is necessary in order to sync the new time value with the underlying
     *     {@link Entry} object that is connected with the <code>mealEntry</code>.
     * </p>
     *
     * @param mealEntry the {@link MealEntry} object to set the time for, not null
     *
     * @param time the new time value, must be in range of [0, 24*60] because of the format: hours*60 + minutes
     *
     */
    public static void setTimeForMealEntry(@NonNull MealEntry mealEntry, @IntRange(from=0, to=24*60) int time) {
        if(mealEntry == null) {
            throw new IllegalArgumentException("'mealEntry' may not be null");
        }

        mealEntry.setTime(time);

        Entry entry = mealEntry.entry;
        if(entry == null) {
            throw new IllegalStateException("'mealEntry' contains no object of type 'Entry'! Something went wrong on creation of the 'mealEntry'");
        }

        /* Syncs the entries time value with the time value for this MealEntry. */
        /* That´s important for sorting a list of all entries. */
        entry.setTime(time);
    }