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Rxjava2 操作符 - Utility

Rxjava2 操作符 - Utility

作者: joker_fu | 来源:发表于2017-10-31 21:57 被阅读165次

Delay —延迟一段指定的时间再发送来自Observable的项目

    private static void delay() {
        Observable
                .create(new ObservableOnSubscribe<Integer>() {
                    @Override
                    public void subscribe(@NonNull ObservableEmitter<Integer> e) throws Exception {
                        System.out.println("emit time: " + System.currentTimeMillis());
                        for (int i = 0; i < 5; i++) {
                            e.onNext(i);
                        }
                    }
                })
                .delay(1, TimeUnit.SECONDS)
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        System.out.println("onNext: " + integer + "time: " + System.currentTimeMillis());
                    }
                });
        while (true) ;
    }

输出结果:

emit time: 1509262337562
onNext: 0time: 1509262338568
onNext: 1time: 1509262338568
onNext: 2time: 1509262338568
onNext: 3time: 1509262338568
onNext: 4time: 1509262338568

Do — 注册一个动作作为原始Observable生命周期事件的一种占位符
主要有doAfterTerminate、doOnComplete、doOnDispose、doOnEach doOnError、doOnLifecycle、doOnNext、doOnSubscribe、 doOnTerminate、onTerminateDetach

    private static void doOnNext() {
        Observable
                .just(1, 2, 3)
                .doOnNext(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        System.out.println("doOnNext " + integer);
                    }
                })
                .doAfterTerminate(new Action() {
                    @Override
                    public void run() throws Exception {
                        System.out.println("doAfterTerminate");
                    }
                })
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        System.out.println("onNext " + integer);
                    }
                });
    }

输出结果:

doOnNext 1
onNext 1
doOnNext 2
onNext 2
doOnNext 3
onNext 3
doAfterTerminate

Materialize/Dematerialize — Materialize将数据项和事件通知都当做数据项发射,Dematerialize刚好相反。Dematerialize操作符是Materialize的逆向过程,它将Materialize转换的结果还原成它原本的形式。

ObserveOn — 指定Observable在一个特定的调度器上发送通知给观察者 (调用观察者的onNext, onCompleted, onError方法)

    private static void observeOn() {
        Observable
                .just(1, 2, 3)
                .observeOn(Schedulers.newThread())
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        System.out.println(Thread.currentThread() + " onNext " + integer);
                    }
                });
        while (true);
    }

输出结果:

Thread[RxNewThreadScheduler-1,5,main] onNext 1
Thread[RxNewThreadScheduler-1,5,main] onNext 2
Thread[RxNewThreadScheduler-1,5,main] onNext 3

Serialize — Observable可以异步调用它的观察者的方法,可能是从不同的线程调用。这可能会让Observable行为不正确,它可能会在某一个onNext调用之前尝试调用onCompleted或onError方法,或者从两个不同的线程同时调用onNext方法。使用Serialize操作符,你可以纠正这个Observable的行为,保证它的行为是正确的且是同步的。

Subscribe — 操作来自Observable的发射物和通知

SubscribeOn — 指定Observable在一个特定的调度器上运转

    private static void subscribeOn() {
        Observable
                .create(new ObservableOnSubscribe<String>() {
                    @Override
                    public void subscribe(@NonNull ObservableEmitter<String> e) throws Exception {
                        for (int i = 0; i < 3; i++) {
                            e.onNext(Thread.currentThread() + " - " + i);
                        }
                    }
                })
                .subscribeOn(Schedulers.io())
                .observeOn(Schedulers.newThread())
                .subscribe(new Consumer<String>() {
                    @Override
                    public void accept(String s) throws Exception {
                        System.out.println(Thread.currentThread() + " onNext " + s);
                    }
                });
        while (true) ;
    }

输出结果:

Thread[RxNewThreadScheduler-1,5,main] onNext Thread[RxCachedThreadScheduler-1,5,main] - 0

Thread[RxNewThreadScheduler-1,5,main] onNext Thread[RxCachedThreadScheduler-1,5,main] - 1

Thread[RxNewThreadScheduler-1,5,main] onNext Thread[RxCachedThreadScheduler-1,5,main] - 2

TimeInterval — 操作符拦截原始Observable发射的数据项,转换为发射表示相邻发射物时间间隔的对象。

    private static void timeInterval() {
        Observable
                .just(1, 2, 3, 4, 5, 6)
                .timeInterval()
                .subscribe(new SafeObserver<Timed<Integer>>(new Observer<Timed<Integer>>() {
                    @Override
                    public void onSubscribe(@NonNull Disposable d) {
                        System.out.println("onSubscribe");
                    }

                    @Override
                    public void onNext(@NonNull Timed<Integer> integerTimed) {
                        System.out.println(integerTimed.time() + " onNext " + integerTimed.value());
                    }

                    @Override
                    public void onError(@NonNull Throwable e) {
                        System.out.println("onError");
                    }

                    @Override
                    public void onComplete() {
                        System.out.println("onComplete");
                    }
                }));
    }

输出结果:

onSubscribe
1 onNext 1
1 onNext 2
0 onNext 3
0 onNext 4
0 onNext 5
0 onNext 6
onComplete

Timeout — 对原始Observable的一个镜像,如果过了一个指定的时长仍没有发射数据,它会发一个错误通知

    private static void timeout() {
        Observable
                .create(new ObservableOnSubscribe<Integer>() {
                    @Override
                    public void subscribe(@NonNull ObservableEmitter<Integer> e) throws Exception {
                        for (int i = 0; i < 5; i++) {
                            Thread.sleep(i * 200);
                            e.onNext(i);
                        }
                    }
                })
                .timeout(500, TimeUnit.MILLISECONDS)
                .subscribe(new Observer<Integer>() {
                    @Override
                    public void onSubscribe(@NonNull Disposable d) {
                        System.out.println("onSubscribe");
                    }

                    @Override
                    public void onNext(@NonNull Integer integer) {
                        System.out.println("onNext " + integer);
                    }

                    @Override
                    public void onError(@NonNull Throwable e) {
                        System.out.println("onError " + e.toString());
                    }

                    @Override
                    public void onComplete() {
                        System.out.println("onComplete");
                    }
                });
        while (true) ;
    }

输出结果:

onSubscribe
onNext 0
onNext 1
onNext 2
onError java.util.concurrent.TimeoutException

Timestamp —给Observable发送的项目加上一个时间戳

    private static void timeStamp() {
        Observable
                .just(1, 2, 3, 4, 5)
                .timestamp(TimeUnit.MILLISECONDS)
                .subscribe(new Consumer<Timed<Integer>>() {
                    @Override
                    public void accept(Timed<Integer> i) throws Exception {
                        System.out.println(i.value() + " - " + i.time());
                    }
                });
    }

输出结果:

1 - 1509456831220
2 - 1509456831221
3 - 1509456831221
4 - 1509456831221
5 - 1509456831221

Using — 创建与Observable具有相同寿命的一次性资源

using操作符接受三个参数:

  • 一个创建一次性资源的
  • 一个创建Observable
  • 一个释放资源的函数
    private static void using() {
        Observable
                .using(new Callable<Integer>() {
                    @Override
                    public Integer call() throws Exception {
                        System.out.println("one ");
                        return 5;
                    }
                }, new Function<Integer, ObservableSource<String>>() {
                    @Override
                    public ObservableSource<String> apply(@NonNull Integer integer) throws Exception {
                        System.out.println("two ");
                        return Observable.just("emit " + integer);
                    }
                }, new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        System.out.println("three ");
                    }
                })
                .subscribe(new Consumer<String>() {
                    @Override
                    public void accept(String s) throws Exception {
                        System.out.println("onNext " + s);
                    }
                });
    }

输出结果:

one
two
onNext emit 5
three

To — 将Observable转换为另一个对象或数据结构
具体有:blockingIterable blockingLatest blockingMostRecent blockingNext sorted to toFuture toList toMap toMultimap toSortedList

    private static void to() {
        Observable
                .just(1, 2, 3, 4, 5)
                .toList()
                .subscribe(new Consumer<List<Integer>>() {
                    @Override
                    public void accept(List<Integer> integers) throws Exception {
                        for (Integer integer : integers) {
                            System.out.println(integer);
                        }
                    }
                });
    }

输出结果:

1
2

3
4
5

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