RxJava笔记 Subject

一、AsyncSubject
Observer会接收AsyncSubject的onComplete()之前的最后一个数据。

 AsyncSubject<String> asyncSubject = AsyncSubject.create();

        asyncSubject.onNext("asyncSubject1");
        asyncSubject.onNext("asyncSubject2");
        asyncSubject.onComplete();

        asyncSubject.subscribe(s -> System.out.println("asyncSubject: " + s));

结果：

asyncSubject: asyncSubject2

二、BehaviorSubject
Observer会先接收到 BehaviorSubject被订阅之前的最后一个数据， 再接收订阅之后发射过 来的数据。

 BehaviorSubject<String> behaviorSubject = BehaviorSubject.create();
        behaviorSubject.onNext("behaviorSubject1");
        behaviorSubject.onNext("behaviorSubject2");

        behaviorSubject.subscribe(s -> System.out.println("behaviorSubject: " + s));

        behaviorSubject.onNext("behaviorSubject3");
        behaviorSubject.onNext("behaviorSubject4");
        behaviorSubject.onComplete();

结果：

behaviorSubject: behaviorSubject2
behaviorSubject: behaviorSubject3
behaviorSubject: behaviorSubject4

三、ReplaySubject
ReplaySubject 会发射所有来自原始 Observable 的数据 给观察者，无论它 们 是何时订阅的。

 ReplaySubject<String> replaySubject = ReplaySubject.create();
        replaySubject.onNext("replaySubject1");
        replaySubject.onNext("replaySubject2");

        replaySubject.subscribe(s -> System.out.println("replaySubject: " + s));

        replaySubject.onNext("replaySubject3");
        replaySubject.onNext("replaySubject4");
        replaySubject.onComplete();

结果：

replaySubject: replaySubject1
replaySubject: replaySubject2
replaySubject: replaySubject3
replaySubject: replaySubject4

四、PublishSubject
Observer 只接收 PublishSubject 被订阅之后发送的数据。

 PublishSubject<String> publishSubject = PublishSubject.create();
        publishSubject.onNext("publishSubject1");
        publishSubject.onNext("publishSubject2");

        publishSubject.subscribe(s -> System.out.println("publishSubject" + s));

        publishSubject.onNext("publishSubject3");
        publishSubject.onNext("publishSubject4");
        publishSubject.onComplete();

结果：

publishSubjectpublishSubject3
publishSubjectpublishSubject4

五、总结
AsyncSubject：不论订阅发生在什么时候，只发射最后一个数据。
BehaviorSubject：发送订阅之前的一个数据和订阅之后的全部数据。
ReplaySubject：不论订阅发生在什么时候，都发射全部数据。
PublishSubject：发送订阅之后全部数据。