RxJava 知識梳理(2) RxJava2 操作符實戰

澤毛發表於2017-12-21
RxJava

一、概述

本文中的所有示例均來自RxJava2這個大神的倉庫，這兩篇文章主要是對示例當中的用法進行一個記錄，方便以後進行查詢。

二、詳細示例

2.1 SimpleExampleActivity

這是一個最簡單的例子，被訂閱者發射了兩個資料（Cricket、Football），並且有一個訂閱者，發生訂閱時，會先回撥onSubscribe(Disposable d)，發射資料後，回撥onNext(String value)方法，最後回撥onComplete()。

    private void doSomeWork() {
        getObservable()
                 //被訂閱者在子執行緒進行操作.
                .subscribeOn(Schedulers.io())
                 //訂閱者在主執行緒處理結果.
                .observeOn(AndroidSchedulers.mainThread()) 
                .subscribe(getObserver());
    }

    private Observable<String> getObservable() {
        return Observable.just("Cricket", "Football");
    }

    private Observer<String> getObserver() {
        return new Observer<String>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(String value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

SimpleExampleActivity.png

2.2 MapExampleActivity

map操作符可以將一個型別的被訂閱者的資料傳給接收另一個型別的訂閱者，即Obervable<T>發射的資料可以傳給Obersever<U>，在轉換的中間，我們需要自己定義轉換的規則，即map(new Function<T, U>())。

    private void doSomeWork() {
        getObservable()
                // Run on a background thread
                .subscribeOn(Schedulers.io())
                // Be notified on the main thread
                .observeOn(AndroidSchedulers.mainThread())
                .map(new Function<List<ApiUser>, List<User>>() {

                    @Override
                    public List<User> apply(List<ApiUser> apiUsers) throws Exception {
                        return Utils.convertApiUserListToUserList(apiUsers);
                    }
                })
                .subscribe(getObserver());
    }

    private Observable<List<ApiUser>> getObservable() {
        return Observable.create(new ObservableOnSubscribe<List<ApiUser>>() {
            @Override
            public void subscribe(ObservableEmitter<List<ApiUser>> e) throws Exception {
                if (!e.isDisposed()) {
                    e.onNext(Utils.getApiUserList());
                    e.onComplete();
                }
            }
        });
    }

    private Observer<List<User>> getObserver() {
        return new Observer<List<User>>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(List<User> userList) {
                textView.append(" onNext");
                textView.append(AppConstant.LINE_SEPARATOR);
                for (User user : userList) {
                    textView.append(" firstName : " + user.firstName);
                    textView.append(AppConstant.LINE_SEPARATOR);
                }
                Log.d(TAG, " onNext : " + userList.size());
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

MapExampleActivity.png

2.3 ZipExampleActivity

zip是Observable的靜態方法，我們通過它傳入n個可以是不同型別的訂閱者，以及一個宣告將這n個被訂閱者組合成一個新的被訂閱者的函式，這個函式的返回值要和訂閱者的型別的Observer<T>的T一致。

    private void doSomeWork() {
        Observable.zip(getCricketFansObservable(), getFootballFansObservable(),
                new BiFunction<List<User>, List<User>, List<User>>() {
                    @Override
                    public List<User> apply(List<User> cricketFans, List<User> footballFans) throws Exception {
                        return Utils.filterUserWhoLovesBoth(cricketFans, footballFans);
                    }
                })
                // Run on a background thread
                .subscribeOn(Schedulers.io())
                // Be notified on the main thread
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getObserver());
    }

    private Observable<List<User>> getCricketFansObservable() {
        return Observable.create(new ObservableOnSubscribe<List<User>>() {
            @Override
            public void subscribe(ObservableEmitter<List<User>> e) throws Exception {
                if (!e.isDisposed()) {
                    e.onNext(Utils.getUserListWhoLovesCricket());
                    e.onComplete();
                }
            }
        });
    }

    private Observable<List<User>> getFootballFansObservable() {
        return Observable.create(new ObservableOnSubscribe<List<User>>() {
            @Override
            public void subscribe(ObservableEmitter<List<User>> e) throws Exception {
                if (!e.isDisposed()) {
                    e.onNext(Utils.getUserListWhoLovesFootball());
                    e.onComplete();
                }
            }
        });
    }

    private Observer<List<User>> getObserver() {
        return new Observer<List<User>>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(List<User> userList) {
                textView.append(" onNext");
                textView.append(AppConstant.LINE_SEPARATOR);
                for (User user : userList) {
                    textView.append(" firstName : " + user.firstName);
                    textView.append(AppConstant.LINE_SEPARATOR);
                }
                Log.d(TAG, " onNext : " + userList.size());
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

ZipExampleActivity.png

2.4 DisposableExampleActivity

    private final CompositeDisposable disposables = new CompositeDisposable();
    
    void doSomeWork() {
        disposables.add(sampleObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeWith(new DisposableObserver<String>() {
                    @Override
                    public void onComplete() {
                        textView.append(" onComplete");
                        textView.append(AppConstant.LINE_SEPARATOR);
                        Log.d(TAG, " onComplete");
                    }

                    @Override
                    public void onError(Throwable e) {
                        textView.append(" onError : " + e.getMessage());
                        textView.append(AppConstant.LINE_SEPARATOR);
                        Log.d(TAG, " onError : " + e.getMessage());
                    }

                    @Override
                    public void onNext(String value) {
                        textView.append(" onNext : value : " + value);
                        textView.append(AppConstant.LINE_SEPARATOR);
                        Log.d(TAG, " onNext value : " + value);
                    }
                }));
    }

    static Observable<String> sampleObservable() {
        return Observable.defer(new Callable<ObservableSource<? extends String>>() {
            @Override
            public ObservableSource<? extends String> call() throws Exception {
                SystemClock.sleep(2000);
                return Observable.just("one", "two", "three", "four", "five");
            }
        });
    }
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DisposableExampleActivity.png

2.5 TakeExampleActivity

take(n)操作，僅發射前n個資料。

    private void doSomeWork() {
        getObservable()
                // Run on a background thread
                .subscribeOn(Schedulers.io())
                // Be notified on the main thread
                .observeOn(AndroidSchedulers.mainThread())
                .take(3)
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.just(1, 2, 3, 4, 5);
    }

    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

TakeExampleActivity.png

2.6 TimerExampleActivity

Observable的靜態方法，它會建立Observable，並在等待指定的時間之後發射唯一的事件。

    private void doSomeWork() {
        getObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getObserver());
    }

    private Observable<? extends Long> getObservable() {
        return Observable.timer(2, TimeUnit.SECONDS);
    }

    private Observer<Long> getObserver() {
        return new Observer<Long>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Long value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果，可以發現即使我們沒有發射任何資料，也會有一個預設值回撥到onNext方法當中：

TimerExampleActivity.png

2.7 IntervalExampleActivity

interval和timer類似，也是Observable的靜態建立方法，它和timer的區別是：它並不是在計時結束後就發射唯一的事件，而是每隔一段時間，就發射一次事件，並且Observer會收到遞增的值。

    private void doSomeWork() {
        disposables.add(getObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeWith(getObserver()));
    }

    private Observable<? extends Long> getObservable() {
        return Observable.interval(0, 2, TimeUnit.SECONDS);
    }

    private DisposableObserver<Long> getObserver() {
        return new DisposableObserver<Long>() {

            @Override
            public void onNext(Long value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

IntervalExampleActivity.png

2.8 SingleObserverExampleActivity

SingleObserver屬於Observer的一種，它和普通Observer的不同，在於其回撥方法，它沒有onNext(T t)方法，而是隻有onSuccess(T t)方法。

    private void doSomeWork() {
        Single.just("Amit").subscribe(getSingleObserver());
    }

    private SingleObserver<String> getSingleObserver() {
        return new SingleObserver<String>() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onSuccess(String value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }
        };
    }
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執行結果：

SingleObserverExampleActivity.png

2.9 CompletableObserverExampleActivity

CompletableObserver也是屬於Observer的一種，它只有onComplete回撥，而沒有類似與onNext之間的引數回撥。

    private void doSomeWork() {
        Completable completable = Completable.timer(1000, TimeUnit.MILLISECONDS);
        completable
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getCompletableObserver());
    }

    private CompletableObserver getCompletableObserver() {
        return new CompletableObserver() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }
        };
    }
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執行結果：

CompletableObserverExampleActivity.png

2.10 FlowableExampleActivity

    private void doSomeWork() {
        Flowable<Integer> observable = Flowable.just(1, 2, 3, 4);
        observable.reduce(50, new BiFunction<Integer, Integer, Integer>() {
            @Override
            public Integer apply(Integer t1, Integer t2) {
                return t1 + t2;
            }
        }).subscribe(getObserver());
    }

    private SingleObserver<Integer> getObserver() {

        return new SingleObserver<Integer>() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onSuccess(Integer value) {
                textView.append(" onSuccess : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onSuccess : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }
        };
    }
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執行結果：

FlowableExampleActivity.png

2.11 ReduceExampleActivity

reduce是把發射序列內值進行兩兩比較，直到比較出最值，如果序列的長度小於2，那麼不會被回撥。

    private void doSomeWork() {
        getObservable().reduce(new BiFunction<Integer, Integer, Integer>() {
                    @Override
                    public Integer apply(Integer t1, Integer t2) {
                        return t1 + t2;
                    }
                }).subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.just(1, 2, 3, 4);
    }

    private MaybeObserver<Integer> getObserver() {
        return new MaybeObserver<Integer>() {
            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onSuccess(Integer value) {
                textView.append(" onSuccess : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onSuccess : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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2.12 BufferExampleActivity

buffer(a, b)，a表示陣列的最大長度，b表示步長。

    private void doSomeWork() {
        Observable<List<String>> buffered = getObservable().buffer(3, 1);
        buffered.subscribe(getObserver());
    }

    private Observable<String> getObservable() {
        return Observable.just("one", "two", "three", "four", "five");
    }

    private Observer<List<String>> getObserver() {
        return new Observer<List<String>>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(List<String> stringList) {
                textView.append(" onNext size : " + stringList.size());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : size :" + stringList.size());
                for (String value : stringList) {
                    textView.append(" value : " + value);
                    textView.append(AppConstant.LINE_SEPARATOR);
                    Log.d(TAG, " : value :" + value);
                }

            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

BufferExampleActivity.png

2.13 FilterExampleActivity

filter操作符需要傳入一個條件函式，僅當發射的資料滿足該條件時，訂閱者才會收到資料。

    private void doSomeWork() {
        Observable.just(1, 2, 3, 4, 5, 6)
                .filter(new Predicate<Integer>() {
                    @Override
                    public boolean test(Integer integer) throws Exception {
                        return integer % 2 == 0;
                    }
                })
                .subscribe(getObserver());
    }


    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : ");
                textView.append(AppConstant.LINE_SEPARATOR);
                textView.append(" value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext ");
                Log.d(TAG, " value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

FilterExampleActivity.png

2.14 SkipExampleActivity

skip(n)操作符，會跳過前n個結果。

    private void doSomeWork() {
        getObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .skip(2)
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.just(1, 2, 3, 4, 5);
    }

    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

SkipExampleActivity.png

2.15 ScanExampleActivity

scan操作符通過遍歷被訂閱者產生的結果，依次對每一個結果項按照指定規則進行運算，計算後的結果作為下一個迭代項引數，每一次迭代項都會把計算結果輸出給訂閱者。

    private void doSomeWork() {
        getObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .scan(new BiFunction<Integer, Integer, Integer>() {
                    @Override
                    public Integer apply(Integer int1, Integer int2) throws Exception {
                        return int1 + int2;
                    }
                })
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.just(1, 2, 3, 4, 5);
    }

    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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執行結果：

ScanExampleActivity.png

2.16 ReplayExampleActivity

relay(n)，使得即使在未訂閱時，被訂閱者已經發射了資料，訂閱者也可以收到被訂閱者在訂閱之前最多n個資料。

    private void doSomeWork() {
        PublishSubject<Integer> source = PublishSubject.create();
        ConnectableObservable<Integer> connectableObservable = source.replay(3); 
        connectableObservable.connect(); // connecting the connectableObservable
        connectableObservable.subscribe(getFirstObserver());
        source.onNext(1);
        source.onNext(2);
        source.onNext(3);
        source.onNext(4);
        source.onComplete();
        connectableObservable.subscribe(getSecondObserver());
    }

    private Observer<Integer> getFirstObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " First onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" First onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" First onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" First onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onComplete");
            }
        };
    }

    private Observer<Integer> getSecondObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                textView.append(" Second onSubscribe : isDisposed :" + d.isDisposed());
                Log.d(TAG, " Second onSubscribe : " + d.isDisposed());
                textView.append(AppConstant.LINE_SEPARATOR);
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" Second onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" Second onError : " + e.getMessage());
                Log.d(TAG, " Second onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" Second onComplete");
                Log.d(TAG, " Second onComplete");
            }
        };
    }
複製程式碼

執行結果：

ReplayExampleActivity.png

2.17 ConcatExampleActivity

Observable.concat(Observable a, Observable b)，連線兩個被訂閱者，訂閱者將會按照a->b的順序收到兩個被訂閱者所發射的訊息。

    private void doSomeWork() {
        final String[] aStrings = {"A1", "A2", "A3", "A4"};
        final String[] bStrings = {"B1", "B2", "B3"};

        final Observable<String> aObservable = Observable.fromArray(aStrings);
        final Observable<String> bObservable = Observable.fromArray(bStrings);

        Observable.concat(aObservable, bObservable)
                .subscribe(getObserver());
    }


    private Observer<String> getObserver() {
        return new Observer<String>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(String value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
複製程式碼

執行結果：

ConcatExampleActivity.png

2.18 MergeExampleActivity

merge和concat類似，也是用來連線兩個被訂閱者，但是它不保證兩個被訂閱發射資料的順序。

    private void doSomeWork() {
        final String[] aStrings = {"A1", "A2", "A3", "A4"};
        final String[] bStrings = {"B1", "B2", "B3"};

        final Observable<String> aObservable = Observable.fromArray(aStrings);
        final Observable<String> bObservable = Observable.fromArray(bStrings);

        Observable.merge(aObservable, bObservable)
                .subscribe(getObserver());
    }


    private Observer<String> getObserver() {
        return new Observer<String>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(String value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
複製程式碼

執行結果：

MergeExampleActivity.png

2.19 DeferExampleActivity

使用defer可以延遲被訂閱者的生成，也就是使得被訂閱者是在訂閱發生時才生成。

    private void doSomeWork() {
        Car car = new Car();
        Observable<String> brandDeferObservable = car.brandDeferObservable();
        car.setBrand("BMW");
        brandDeferObservable.subscribe(getObserver());
    }

    private Observer<String> getObserver() {
        return new Observer<String>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(String value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext : value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
複製程式碼

執行結果：

DeferExampleActivity.png

2.20 DistinctExampleActivity

distinct僅會發射序列當中之前沒有發射過的資料。

    private void doSomeWork() {

        getObservable()
                .distinct()
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.just(1, 2, 1, 1, 2, 3, 4, 6, 4);
    }


    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                Log.d(TAG, " onComplete");
            }
        };
    }
複製程式碼

執行結果：

DistinctExampleActivity.png

2.21 LastOperatorExampleActivity

    private void doSomeWork() {
        getObservable().last("A1") .subscribe(getObserver());
    }

    private Observable<String> getObservable() {
        return Observable.just("A1", "A2", "A3", "A4", "A5", "A6");
    }

    private SingleObserver<String> getObserver() {
        return new SingleObserver<String>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onSuccess(String value) {
                textView.append(" onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext value : " + value);
            }


            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }
        };
    }
複製程式碼

執行結果：

LastOperatorExampleActivity.png

2.22 ReplaySubjectExampleActivity

ReplaySubject使得無論訂閱者在何時訂閱，它們都能收到被訂閱者發射序列中的所有資料。

    private void doSomeWork() {
        ReplaySubject<Integer> source = ReplaySubject.create();
        source.subscribe(getFirstObserver());
        source.onNext(1);
        source.onNext(2);
        source.onNext(3);
        source.onNext(4);
        source.onComplete();
        source.subscribe(getSecondObserver());
    }

    private Observer<Integer> getFirstObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " First onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" First onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" First onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" First onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onComplete");
            }
        };
    }

    private Observer<Integer> getSecondObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                textView.append(" Second onSubscribe : isDisposed :" + d.isDisposed());
                Log.d(TAG, " Second onSubscribe : " + d.isDisposed());
                textView.append(AppConstant.LINE_SEPARATOR);
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" Second onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" Second onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" Second onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onComplete");
            }
        };
    }
複製程式碼

執行結果：

ReplaySubjectExampleActivity.png

2.23 PublishSubjectExampleActivity

如果使用了PublishSubject，那麼對於訂閱者來說，它們只會收到被訂閱者在訂閱之後發射的序列。

    private void doSomeWork() {
        PublishSubject<Integer> source = PublishSubject.create();
        source.onNext(1);
        source.onNext(2);
        source.onNext(3);
        source.subscribe(getSecondObserver());
        source.onNext(4);
        source.onComplete();
    }


    private Observer<Integer> getFirstObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " First onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" First onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" First onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" First onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onComplete");
            }
        };
    }

    private Observer<Integer> getSecondObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                textView.append(" Second onSubscribe : isDisposed :" + d.isDisposed());
                Log.d(TAG, " Second onSubscribe : " + d.isDisposed());
                textView.append(AppConstant.LINE_SEPARATOR);
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" Second onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" Second onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" Second onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onComplete");
            }
        };
    }
複製程式碼

執行結果：

PublishSubjectExampleActivity.png

2.24 BehaviorSubjectExampleActivity

如果使用了BehaviorSubject這個被訂閱者，那麼被訂閱者收到的序列和它訂閱的時間點有關，被訂閱者會收到發生訂閱之前最近一次的發射的值（如果之前沒有發射任何值，那麼有可能是一個種子/預設值），以及從訂閱時刻到整個序列完成的序列。

    private void doSomeWork() {
        BehaviorSubject<Integer> source = BehaviorSubject.create();
        source.subscribe(getFirstObserver()); // it will get 1, 2, 3, 4 and onComplete
        source.onNext(1);
        source.onNext(2);
        source.onNext(3);
        source.subscribe(getSecondObserver());
        source.onNext(4);
        source.onComplete();
    }


    private Observer<Integer> getFirstObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " First onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" First onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" First onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" First onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onComplete");
            }
        };
    }

    private Observer<Integer> getSecondObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                textView.append(" Second onSubscribe : isDisposed :" + d.isDisposed());
                Log.d(TAG, " Second onSubscribe : " + d.isDisposed());
                textView.append(AppConstant.LINE_SEPARATOR);
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" Second onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" Second onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" Second onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onComplete");
            }
        };
    }
複製程式碼

執行結果：

BehaviorSubjectExampleActivity.png

2.25 AsyncSubjectExampleActivity

如果使用了AsyncSubject這個被訂閱者，那麼它所有的訂閱者只會在被訂閱者整個序列發射完成之後才能收到值，並且僅僅會收到整個發射序列的最後一個值。如果訂閱者沒有發射任何一個值，那麼所有的被訂閱者都不會收到除完成之外的其它訊息。

    private void doSomeWork() {
        AsyncSubject<Integer> source = AsyncSubject.create();
        source.subscribe(getFirstObserver()); //第一個訂閱者.
        source.onNext(1);
        source.onNext(2);
        source.onNext(3);
        source.subscribe(getSecondObserver()); //第二個訂閱者.
        source.onNext(4);
        source.onComplete();
    }

    private Observer<Integer> getFirstObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " First onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" First onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" First onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" First onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " First onComplete");
            }
        };
    }

    private Observer<Integer> getSecondObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                textView.append(" Second onSubscribe : isDisposed :" + d.isDisposed());
                Log.d(TAG, " Second onSubscribe : " + d.isDisposed());
                textView.append(AppConstant.LINE_SEPARATOR);
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" Second onNext : value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onNext value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" Second onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" Second onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " Second onComplete");
            }
        };
    }
複製程式碼

執行結果：

AsyncSubjectExampleActivity.png

2.26 ThrottleFirstExampleActivity

throttleFirst用來解決抖動的問題，我們可以設定一段時間，之後它會發射固定時間長度之內的第一個事件，而遮蔽其它的事件。

    private void doSomeWork() {
        getObservable()
                .throttleFirst(500, TimeUnit.MILLISECONDS)
                // Run on a background thread
                .subscribeOn(Schedulers.io())
                // Be notified on the main thread
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                // send events with simulated time wait
                Thread.sleep(0);
                emitter.onNext(1); // deliver
                emitter.onNext(2); // skip
                Thread.sleep(505);
                emitter.onNext(3); // deliver
                Thread.sleep(99);
                emitter.onNext(4); // skip
                Thread.sleep(100);
                emitter.onNext(5); // skip
                emitter.onNext(6); // skip
                Thread.sleep(305);
                emitter.onNext(7); // deliver
                Thread.sleep(510);
                emitter.onComplete();
            }
        });
    }

    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : ");
                textView.append(AppConstant.LINE_SEPARATOR);
                textView.append(" value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext ");
                Log.d(TAG, " value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
複製程式碼

執行結果：

ThrottleFirstExampleActivity.png

2.27 ThrottleLastExampleActivity

throttleLast和throttleFirst類似，都是設定固定的時間長度，但是它發射的是這個時間段內的最後一個事件，而不是第一個事件。

    private void doSomeWork() {
        getObservable()
                .throttleLast(500, TimeUnit.MILLISECONDS)
                // Run on a background thread
                .subscribeOn(Schedulers.io())
                // Be notified on the main thread
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                // send events with simulated time wait
                Thread.sleep(0);
                emitter.onNext(1); // skip
                emitter.onNext(2); // deliver
                Thread.sleep(505);
                emitter.onNext(3); // skip
                Thread.sleep(99);
                emitter.onNext(4); // skip
                Thread.sleep(100);
                emitter.onNext(5); // skip
                emitter.onNext(6); // deliver
                Thread.sleep(305);
                emitter.onNext(7); // deliver
                Thread.sleep(510);
                emitter.onComplete();
            }
        });
    }

    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : ");
                textView.append(AppConstant.LINE_SEPARATOR);
                textView.append(" value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext ");
                Log.d(TAG, " value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
複製程式碼

執行結果：

ThrottleLastExampleActivity.png

2.28 DebounceExampleActivity

Observable.debounce(float value, Unit unit)，dounce，被訂閱者在收到要發射訊息的指令後，會等待一段時間，如果在這段時間內沒有新的訊息發射指令，那麼它會發射這條訊息，否則它會丟棄掉它，從這個新收到的值開始重新等待設定的時間長度。

    private void doSomeWork() {
        getObservable()
                .debounce(500, TimeUnit.MILLISECONDS)
                // Run on a background thread
                .subscribeOn(Schedulers.io())
                // Be notified on the main thread
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getObserver());
    }

    private Observable<Integer> getObservable() {
        return Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                // send events with simulated time wait
                emitter.onNext(1); // skip
                Thread.sleep(400);
                emitter.onNext(2); // deliver
                Thread.sleep(505);
                emitter.onNext(3); // skip
                Thread.sleep(100);
                emitter.onNext(4); // deliver
                Thread.sleep(605);
                emitter.onNext(5); // deliver
                Thread.sleep(510);
                emitter.onComplete();
            }
        });
    }

    private Observer<Integer> getObserver() {
        return new Observer<Integer>() {

            @Override
            public void onSubscribe(Disposable d) {
                Log.d(TAG, " onSubscribe : " + d.isDisposed());
            }

            @Override
            public void onNext(Integer value) {
                textView.append(" onNext : ");
                textView.append(AppConstant.LINE_SEPARATOR);
                textView.append(" value : " + value);
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onNext ");
                Log.d(TAG, " value : " + value);
            }

            @Override
            public void onError(Throwable e) {
                textView.append(" onError : " + e.getMessage());
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onError : " + e.getMessage());
            }

            @Override
            public void onComplete() {
                textView.append(" onComplete");
                textView.append(AppConstant.LINE_SEPARATOR);
                Log.d(TAG, " onComplete");
            }
        };
    }
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2.29 WindowExampleActivity

每隔ns集中發射這段時間內的資料，而不是一有資料就發射。

    protected void doSomeWork() {
        Observable.interval(1, TimeUnit.SECONDS).take(12)
                .window(3, TimeUnit.SECONDS)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getConsumer());
    }

    public Consumer<Observable<Long>> getConsumer() {
        return new Consumer<Observable<Long>>() {
            @Override
            public void accept(Observable<Long> observable) throws Exception {
                Log.d(TAG, "Sub Divide begin....");
                textView.append("Sub Divide begin ....");
                textView.append(AppConstant.LINE_SEPARATOR);
                observable
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe(new Consumer<Long>() {
                            @Override
                            public void accept(Long value) {
                                Log.d(TAG, "Next:" + value);
                                textView.append("Next:" + value);
                                textView.append(AppConstant.LINE_SEPARATOR);
                            }
                        });
            }
        };
    }
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