如何创建一个可以取消订阅和重新订阅的可观察序列?

编程入门行业动态更新时间:2024-10-18 01:31:39

本文介绍了如何创建一个可以取消订阅和重新订阅的可观察序列?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！问题描述

我有一个相当复杂的功能，我想被动地实现.是否启用此功能取决于以下内容

I have a fairly complex feature I want to implement reactively. Whether this feature is enabled depends on the following

已启用此功能的用户首选项(用户可以打开或关闭此功能)

活动已启动 (Activity#onStart()).如果您不熟悉 Android，这仅表示该视图对用户可见.

User preference for this feature has been enabled (user can toggle this feature on or off)

Activity is started (Activity#onStart()). If you aren't familiar with Android, this is just means the view is visible to the user.

以下是我已有的可观察对象.

Here are the following observables I already have.

Observable - 是否启用此功能的用户首选项.true 如果启用，false 如果禁用.

Observable - LifeCycleEvent 是一个与 Android 活动生命周期相关的枚举.

Observable<Boolean> - a user preference for whether this feature is enabled. true if enabled, false if disabled.

Observable<LifeCycleEvent> - LifeCycleEvent is an enum that relates to Android's activity lifecycle.

Observable 和 Observable 订阅后，启动一个流程密集型任务以启用我的功能.这两个 observable 需要成为

Observable<Void> and Observable<Void>, when subscribed to, kick off a process intensive task to enable my feature.. These two observables need to be

订阅当 #2 发出 LifeCycleEvent#isStarted() 返回 true 和 #1 发出 true 的事件(用户启用的功能)
取消订阅当 #2 发出 LifeCycleEvent#isStarted() 返回 false
在#2 发出LifeCycleEvent#isDestoryed() 返回true 的事件时取消订阅.我还需要在这里取消订阅 #1 和 #2，因为这意味着该类已准备好进行垃圾收集.
从 #1 发出 false 时取消订阅(用户未启用此功能)

subscribed to when #2 emits an event that LifeCycleEvent#isStarted() returns true and #1 emits true (user enabled feature)
unsubscribed to when #2 emits an event that LifeCycleEvent#isStarted() returns false
unsubscribed to when #2 emits an event that LifeCycleEvent#isDestoryed() returns true. I will also need to unsubscribe from #1 and #2 here because that means this class is ready for garbage collection.
unsubscribed from when #1 emits false (user did not enabled this feature)

我怎样才能最好地做到这一点?我有一个类将采用上述依赖项和一个名为 void startObserving() 的方法，它将启动观察过程(并在此实例的生命周期内调用一次.我想我需要以某种方式维护两个订阅(一个用于 #1 和 #2，另一个用于 #3).

How can I best do this? I have a single class that will take the above mentioned dependencies and a single method called void startObserving() that will kick the observation process off (and be called once for the lifetime of this instance. I think I will need to somehow maintain two subscriptions (one for #1 & #2, and another for #3).

推荐答案

哦，这是一个难题，我认为:

Oooh, this is a puzzler, I think:

Observable<Boolean> featureEnabled = ...; Observable<LivecycleEvent> lifecycle = ... .filter(event -> event.isStarted() !=null || event.isDestroyed()); Observable<Void> processA = ...; Observable<Void> processB = ...; Observable<Void> processes = Observable.merge(processA, processB); ObservablebineLatest(featureEnabled, lifecycle, (feature, event) -> Pair.of(feature && event.isStarted(), event.isDestroyed())) .takeUntil(pair -> pair.getRight()) .map(Pair::getLeft) .debounceUntilChanged() .switchMap(flag -> flag ? processes : Observable.empty()) .subscribe(....)