RxJava2 入门详细笔记（2）

六、过滤操作符

6.1、filter()

通过一定逻辑来过滤被观察者发送的事件，如果返回 true 则会发送事件，否则不会发送

 Observable.just(1, 2, 3, 4).filter(new Predicate<Integer>() { @Override public boolean test(Integer integer) throws Exception { return integer % 2 == 0; } }).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 07:57:48.196 12753-12753/? E/MainActivity: accept : 2 10-06 07:57:48.196 12753-12753/? E/MainActivity: accept : 4 

6.2、ofType()

过滤不符合该类型的事件

 Observable.just(1, 2, "Hi", 3, 4, "Hello").ofType(Integer.class).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 1 10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 2 10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 3 10-06 07:59:41.265 12857-12857/leavesc.hello.rxjavademo E/MainActivity: accept : 4 

6.3、skip()

以正序跳过指定数量的事件

 Observable.just(1, 2, 3, 4).skip(2).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 08:01:09.183 12971-12971/leavesc.hello.rxjavademo E/MainActivity: accept : 3 10-06 08:01:09.183 12971-12971/leavesc.hello.rxjavademo E/MainActivity: accept : 4 

6.4、skipLast()

以反序跳过指定数量的事件

 Observable.just(1, 2, 3, 4).skipLast(2).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 08:02:00.753 13079-13079/leavesc.hello.rxjavademo E/MainActivity: accept : 1 10-06 08:02:00.753 13079-13079/leavesc.hello.rxjavademo E/MainActivity: accept : 2 

6.5、distinct()

过滤事件序列中的重复事件

 Observable.just(1, 2, 1, 2, 3, 4, 3).distinct().subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 1 10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 2 10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 3 10-06 08:03:27.402 13189-13189/leavesc.hello.rxjavademo E/MainActivity: accept : 4 

6.6、distinctUntilChanged()

过滤掉连续重复的事件

 Observable.just(1, 2, 2, 1, 3, 4, 3, 3).distinctUntilChanged().subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 08:04:44.531 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 1 10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 2 10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 1 10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 3 10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 4 10-06 08:04:44.541 13294-13294/leavesc.hello.rxjavademo E/MainActivity: accept : 3 

6.7、take()

控制观察者接收事件的数量

 Observable.just(1, 2, 2, 1, 3, 4, 3, 3).take(3).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 08:05:43.520 13397-13397/? E/MainActivity: accept : 1 10-06 08:05:43.520 13397-13397/? E/MainActivity: accept : 2 10-06 08:05:43.520 13397-13397/? E/MainActivity: accept : 2 

6.8、debounce()

如果两个事件发送的时间间隔小于设定的时间间隔，则前一件事件不会发送给观察者

 Observable.create(new ObservableOnSubscribe<Integer>() { @Override public void subscribe(ObservableEmitter<Integer> emitter) throws Exception { emitter.onNext(1); Thread.sleep(900); emitter.onNext(2); } }).debounce(1, TimeUnit.SECONDS).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

10-06 08:08:59.337 13509-13523/leavesc.hello.rxjavademo E/MainActivity: accept : 2 

6.9、firstElement() && lastElement()

firstElement() 取事件序列的第一个元素，lastElement() 取事件序列的最后一个元素

 Observable.just(1, 2, 3, 4, 5).firstElement().subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

6.10、elementAt() & elementAtOrError()

elementAt() 可以指定取出事件序列中事件，但是输入的 index 超出事件序列的总数的话就不会触发任何调用，想触发异常信息的话就用 elementAtOrError()

 Observable.just(1, 2, 3, 4, 5).elementAt(5).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

以上代码不会触发任何

改用为 elementAtOrError()，则会抛出异常

 Observable.just(1, 2, 3, 4, 5).elementAtOrError(5).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept : " + integer); } }); 

Process: leavesc.hello.rxjavademo, PID: 13948 io.reactivex.exceptions.OnErrorNotImplementedException: The exception was not handled due to missing onError handler in the subscribe() method call. Further reading: https://github.com/ReactiveX/RxJava/wiki/Error-Handling | null at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704) at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701) at io.reactivex.internal.observers.ConsumerSingleObserver.onError(ConsumerSingleObserver.java:46) at io.reactivex.internal.operators.observable.ObservableElementAtSingle$ElementAtObserver.onComplete(ObservableElementAtSingle.java:115) at io.reactivex.internal.operators.observable.ObservableFromArray$FromArrayDisposable.run(ObservableFromArray.java:111) at io.reactivex.internal.operators.observable.ObservableFromArray.subscribeActual(ObservableFromArray.java:37) at io.reactivex.Observable.subscribe(Observable.java:12090) at io.reactivex.internal.operators.observable.ObservableElementAtSingle.subscribeActual(ObservableElementAtSingle.java:37) at io.reactivex.Single.subscribe(Single.java:3438) at io.reactivex.Single.subscribe(Single.java:3424) 

七、条件操作符

7.1、all()

判断事件序列是否全部满足某个事件，如果都满足则返回 true，反之则返回 false

 Observable.just(1, 2, 3, 4, 5).all(new Predicate<Integer>() { @Override public boolean test(Integer integer) throws Exception { return integer % 2 == 0; } }).subscribe(new Consumer<Boolean>() { @Override public void accept(Boolean aBoolean) throws Exception { Log.e(TAG, "accept: " + aBoolean); } }); 

10-06 08:16:10.212 14043-14043/leavesc.hello.rxjavademo E/MainActivity: accept: false 

7.2、takeWhile()

发射原始 Observable，直到指定的某个条件不成立的那一刻，它停止发射原始 Observable，并终止自己的 Observable

Observable.just(1, 2, 3, 4, 5, 1, 2).takeWhile(new Predicate<Integer>() { @Override public boolean test(Integer integer) throws Exception { return integer < 4; } }).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept: " + integer); } }); 

10-06 14:03:42.110 20095-20095/leavesc.hello.rxjavademo E/MainActivity: accept: 1 10-06 14:03:42.110 20095-20095/leavesc.hello.rxjavademo E/MainActivity: accept: 2 10-06 14:03:42.110 20095-20095/leavesc.hello.rxjavademo E/MainActivity: accept: 3 

7.3、skipWhile()

订阅原始的 Observable，但是忽略它的发射物，直到指定的某个条件变为 false 时才开始发射原始 Observable

 Observable.just(1, 2, 4, 1, 3, 4, 5, 1, 5) .skipWhile(new Predicate<Integer>() { @Override public boolean test(Integer integer) throws Exception { return integer < 3; } }) .subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "integer " + integer); } }); 

10-06 13:59:40.583 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 4 10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 1 10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 3 10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 4 10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 5 10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 1 10-06 13:59:40.593 19764-19764/leavesc.hello.rxjavademo E/MainActivity: integer 5 

7.4、takeUntil()

用于设置一个条件，当事件满足此条件时，此事件会被发送，但之后的事件就不会被发送了

Observable.just(1, 2, 4, 1, 3, 4, 5, 1, 5) .takeUntil(new Predicate<Integer>() { @Override public boolean test(Integer integer) throws Exception { return integer > 3; } }) .subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "integer " + integer); } }); 

10-06 08:54:24.833 17208-17208/? E/MainActivity: integer 1 10-06 08:54:24.833 17208-17208/? E/MainActivity: integer 2 10-06 08:54:24.833 17208-17208/? E/MainActivity: integer 4 

7.5、skipUntil()

当 skipUntil() 中的 Observable 发送事件了，原始的 Observable 才会发送事件给观察者

Observable.intervalRange(1, 6, 0, 1, TimeUnit.SECONDS) .skipUntil(Observable.intervalRange(10, 3, 1, 1, TimeUnit.SECONDS)) .subscribe(new Observer<Long>() { @Override public void onSubscribe(Disposable d) { Log.e(TAG, "onSubscribe"); } @Override public void onNext(Long along) { Log.e(TAG, "onNext : " + along); } @Override public void onError(Throwable e) { Log.e(TAG, "onError"); } @Override public void onComplete() { Log.e(TAG, "onComplete"); } }); 

10-06 08:51:16.926 16877-16877/leavesc.hello.rxjavademo E/MainActivity: onSubscribe 10-06 08:51:17.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 2 10-06 08:51:18.936 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 3 10-06 08:51:19.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 4 10-06 08:51:20.936 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 5 10-06 08:51:21.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onNext : 6 10-06 08:51:21.946 16877-16892/leavesc.hello.rxjavademo E/MainActivity: onComplete 

7.6、sequenceEqual()

判断两个 Observable 发送的事件是否相同，如果两个序列是相同的（相同的数据，相同的顺序，相同的终止状态），它就发射 true，否则发射 false

 Observable.sequenceEqual(Observable.just(1, 2, 3), Observable.just(1, 2, 3)) .subscribe(new Consumer<Boolean>() { @Override public void accept(Boolean aBoolean) throws Exception { Log.e(TAG, "accept aBoolean : " + aBoolean); } }); 

10-06 08:46:59.369 16492-16492/leavesc.hello.rxjavademo E/MainActivity: accept aBoolean : true 

7.7、contains()

判断事件序列中是否含有某个元素，如果有则返回 true，如果没有则返回 false

 Observable.just(1, 2, 3, 4).contains(2).subscribe(new Consumer<Boolean>() { @Override public void accept(Boolean aBoolean) throws Exception { Log.e(TAG, "accept aBoolean : " + aBoolean); } }); 

10-06 08:45:58.100 16386-16386/leavesc.hello.rxjavademo E/MainActivity: accept aBoolean : true 

7.8、isEmpty()

判断事件序列是否为空

 Observable.create(new ObservableOnSubscribe<Integer>() { @Override public void subscribe(ObservableEmitter<Integer> emitter) throws Exception { emitter.onComplete(); } }).isEmpty().subscribe(new Consumer<Boolean>() { @Override public void accept(Boolean aBoolean) throws Exception { Log.e(TAG, "accept aBoolean: " + aBoolean); } }); 

10-06 08:43:43.201 16278-16278/leavesc.hello.rxjavademo E/MainActivity: accept aBoolean: true 

7.9、amb()

amb() 接收一个 Observable 集合，但是只会发送最先发送事件的 Observable 中的事件，不管发射的是一项数据还是一个 onError 或 onCompleted 通知，其余 Observable 将会被丢弃

 List<Observable<Long>> list = new ArrayList<>(); list.add(Observable.intervalRange(1, 3, 2, 1, TimeUnit.SECONDS)); list.add(Observable.intervalRange(10, 3, 0, 1, TimeUnit.SECONDS)); Observable.amb(list).subscribe(new Consumer<Long>() { @Override public void accept(Long aLong) throws Exception { Log.e(TAG, "accept: " + aLong); } }); 

10-06 08:41:45.783 16053-16068/leavesc.hello.rxjavademo E/MainActivity: accept: 10 10-06 08:41:46.783 16053-16068/leavesc.hello.rxjavademo E/MainActivity: accept: 11 10-06 08:41:47.783 16053-16068/leavesc.hello.rxjavademo E/MainActivity: accept: 12 

7.10、defaultIfEmpty()

如果 Observable 没有发射任何值，则可以利用这个方法发送一个默认值

 Observable.create(new ObservableOnSubscribe<Integer>() { @Override public void subscribe(ObservableEmitter<Integer> emitter) throws Exception { emitter.onComplete(); } }).defaultIfEmpty(100).subscribe(new Consumer<Integer>() { @Override public void accept(Integer integer) throws Exception { Log.e(TAG, "accept: " + integer); } }); 

10-06 08:40:04.754 15945-15945/leavesc.hello.rxjavademo E/MainActivity: accept: 100 

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