在Android领域 - 如何选择由IDS（@PrimaryKey）的列表中选择多个对象？ [英] Realm on Android - How to select multiple objects by list of ids (@PrimaryKey)?

问题描述

我建立一个Android应用程序与数据库领域

I'm building an Android app with the Realm database.

我文章叫做 RealmObject 子类，有一个 ID 字段（它和 INT ，也是一个 @PrimaryKey ）。我想传递给查询 INT S（一设置， int的列表[] ，或其他）文章编号的，并且只检索这些条款。

I have a RealmObject subclass called Article which has an id field (it's and int and also a @PrimaryKey). I would like to pass to a query a list of ints (a Set, int[], or whatever) of article id's and retrieve only those articles.

在SQL会是这样的：

SELECT *
FROM `table`
where ID in (5263, 5625, 5628, 5621) 

我已经看到了它有可能做到这一点iOS中的这个计算器问题。

我怎样才能做到这在Android中？谢谢！

How can I do this in Android? Thanks!

编辑：只是为了告知，我也问过这个在GitHub库的这里。

Just to inform, I also asked this on the GitHub repo here.

推荐答案

这@ChristianMelchior答案返回所有文章，如果ID列表是空的。我希望它返回一个空 RealmResults＆lt;物品＆GT; 。这就是我最后做;

The answer from @ChristianMelchior returns all articles if the list of ids is empty. I want it to return an empty RealmResults<Article>. That's what I've ended up doing;

Set<Integer> articleIds = this.getArticleIds();
RealmQuery<Article> query = realm.where(Article.class);
if (articleIds.size() == 0) {
    // We want to return an empty list if the list of ids is empty. 
    // Just search for an id that does not exist.
    query = query.equalTo("id", -30000);
} else {
    int i = 0;
    for (int id : articleIds) {
        // The or() operator requires left hand and right hand elements. 
        // If articleIds had only one element then it would crash with
        // "Missing right-hand side of OR"
        if (i++ > 0) {
            query = query.or();
        }
        query = query.equalTo("id", id);
    }
}
return query.findAll();

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