android - RxJava : BehaviorSubject not receiving subsequent emissions from source Observable

Question

我在尝试使用 BehaviorSubject(通过 RxRelay.BehaviorRelay)存储来自连续 Observable 的最新发射时遇到问题.

“连续”是指源 Observable 旨在在底层数据集发生变化时发出数据。

BehaviorSubject 订阅了源 Observable。

看来，一旦我订阅了 BehaviorSubject，我似乎只会收到从源 Observable 发送到 BehaviorSubject 的第一个值>。源 Observable 似乎不再持续发射，事实上，停止发射更多项目。

所以，这里有一个有点做作的例子:

//A Singleton
public class DataManager {

    private Observable<List<Item>> itemsObservable;

    //A BehaviorRelay (BehaviorSubject)
    public BehaviorRelay<List<Item>> itemsRelay = BehaviorRelay.create();

    private DataManager() {

        //An Observable which emits when subscribed, and then subsequently when the underlying uri's data changes
        itemsObservable = SqlBrite.createQuery(Uri uri, ...);

        //In practice I would lazily subscribe to the relay.
        itemsObservable.subscribe(itemsRelay);
    }
}

现在，从某处订阅 BehaviorSubject:

// Subscribe to the BehaviorSubject
DataManager.getInstance.itemsObservable.subscribe(items -> {
    //Here, I would expect 'items' to be the most recent List<Item> emitted from the source Observable to the BehaviorSubject.
    //However, it seems like it's only ever the *first* item emitted from the source Observable to the BehaviorSubject.
    //It seems like the source Observable never emits to the BehaviorSubject more than once, despite the source's underlying 
    //dataset having changed (I am triggering this change in testing).
});

Answer 1

结果证明我的测试存在缺陷。支持 SqlBrite Observable 的 uri 未收到更改通知，因此 Observable 未发出任何新值。在 onResume 生命周期方法中重新订阅 Subject 也有一些误会。所有工作都按预期进行。