take()

Observable.just(1, 2, 3, 4, 5)

.subscribeOn(Schedulers.io())

// Be notified on the main thread

.observeOn(AndroidSchedulers.mainThread())

.take(3)

.subscribe(getObserver())

输出没错是123

我们面来看看源码

直接来看ObservableTake的subscribeActual，[不懂的同学请看我前面的学渣系列]

protected void subscribeActual(Observer super T> observer) {

source.subscribe(new TakeObserver(observer, limit));

}

这个source是ObservableSource的对象。 那么我们去找实现他的Observable

好吧 又回到了。

public final void subscribe(Observer super T> observer)

subscribeActual(observer);

其他的省略了

关键点一步，这回调用了谁的方法呢？ 下面来揭晓

是ObservableObserveOn的subscribeActual

@Override

protected void subscribeActual(Observer super T> observer) {

if (scheduler instanceof TrampolineScheduler) {

source.subscribe(observer);

} else {

Scheduler.Worker w = scheduler.createWorker();

source.subscribe(new ObserveOnObserver(observer, w, delayError, bufferSize));

}

}

看到了吗 又会调用

source.subscribe(new ObserveOnObserver(observer, w, delayError, bufferSize));

然后 又要调用的是ObservableSubscribeOn的subscribeActual

@Override

public void subscribeActual(final Observer super T> s) {

final SubscribeOnObserver parent = new SubscribeOnObserver(s);

s.onSubscribe(parent);

parent.setDisposable(scheduler.scheduleDirect(new Runnable() {

@Override

public void run() {

source.subscribe(parent);

}

}));

}

大家会好奇这两个地方为什么会被调用呢？

下面我给大家看一个地方

.subscribeOn(Schedulers.io())

.observeOn(AndroidSchedulers.mainThread())

O(∩_∩)O

你没有看错

public final Observable observeOn(Scheduler scheduler) {

return observeOn(scheduler, false, bufferSize());

}

public final Observable subscribeOn(Scheduler scheduler) {

ObjectHelper.requireNonNull(scheduler, "scheduler is null");

return RxJavaPlugins.onAssembly(new ObservableSubscribeOn(this, scheduler));

}

大家可以看到不。 这两个方法返回的也是Observable对象。 所以 他们会分别调用这两个对象subscribeActual方法。好吧，让我们来像下进行。

【下面是一个小扩展 给大家一个小小的感觉】

Observable.just(1, 2, 3, 4, 5)

.observeOn(AndroidSchedulers.mainThread())

.take(3)

.subscribe(getObserver())

看到有什么不同了吗？ 我注释掉了一个方法。我为什么要这么干？我注视掉了那么

source.subscribe 会调用谁呢？ 我直接给出来答案。大家可以思考一个 当我直接注释之后会调用just的subscribeActual

public final class ObservableFromArray extends Observable {

final T[] array;

public ObservableFromArray(T[] array) {

this.array = array;

}

@Override

public void subscribeActual(Observer super T> s) {

FromArrayDisposable d = new FromArrayDisposable(s, array);

s.onSubscribe(d);

if (d.fusionMode) {

return;

}

d.run();

}

相信大家看过我之前的应该可以看懂。

让我们回归正题当执行到ObservableSubscribeOn的subscribeActual的方法的时候

public void subscribeActual(final Observer super T> s) {

final SubscribeOnObserver parent = new SubscribeOnObserver(s);

s.onSubscribe(parent);

parent.setDisposable(scheduler.scheduleDirect(new Runnable() {

@Override

public void run() {

source.subscribe(parent);

}

}));

source.subscribe(parent); 看到这个方法了吗、首先它是异步的。另外执行

.source.subscribe(parent);的时候 ，实际上就执行了ObservableFromArray的subscribeActual

public void subscribeActual(Observer super T> s) {

FromArrayDisposable d = new FromArrayDisposable(s, array);

s.onSubscribe(d);

if (d.fusionMode) {

return;

}

d.run();

剩下的就好理解了，都是分别执行onnext等方法。

到这里task的大体思路介绍完毕

2下面开始timer 定时器

public Disposable scheduleDirect(@NonNull Runnable run, long delay, @NonNull TimeUnit unit) {

final Worker w = createWorker();

final Runnable decoratedRun = RxJavaPlugins.onSchedule(run);

w.schedule(new Runnable() {

@Override

public void run() {

try {

decoratedRun.run();

} finally {

w.dispose();

}

}

}, delay, unit);

return w;

}

重复的就不贴了。 都是差不多重复的。 只是给大家贴上关键代码

看到这里面了吗。delay 就是大家贴上的时间。 详细这个大家都是可以看明白的。，

3interval

做周期性操作，从翻译上大家就应该可以看明白

ComputationScheduler的schedulePeriodicallyDirect的方法

public Disposable schedulePeriodicallyDirect(@NonNull Runnable run, long initialDelay, long period, TimeUnit unit) {

PoolWorker w = pool.get().getEventLoop();

return w.schedulePeriodicallyDirect(run, initialDelay, period, unit);

}

NewThreadWorker的schedulePeriodicallyDirect的方法

public Disposable schedulePeriodicallyDirect(final Runnable run, long initialDelay, long period, TimeUnit unit) {

Runnable decoratedRun = RxJavaPlugins.onSchedule(run);

try {

Future> f = executor.scheduleAtFixedRate(decoratedRun, initialDelay, period, unit);

return Disposables.fromFuture(f);

} catch (RejectedExecutionException ex) {

RxJavaPlugins.onError(ex);

return EmptyDisposable.INSTANCE;

}

}

分别设置了 什么时候开始。多长时间执行一次

4buffer

Observable> buffered = getObservable().buffer(3, 2);

buffered.subscribe(getObserver());

ObservableBuffer的subscribeActual的方法

protected void subscribeActual(Observer super U> t) {

if (skip == count) {

BufferExactObserver bes = new BufferExactObserver(t, count, bufferSupplier);

if (bes.createBuffer()) {

source.subscribe(bes);

}

} else {

source.subscribe(new BufferSkipObserver(t, count, skip, bufferSupplier));

}

}

好吧到了关键的地方 source.subscribe是调用谁的地方

Observable.just("one", "two", "three", "four", "five");

所以是ObservableFromArray的subscribeActual方法

public void subscribeActual(Observer super T> s) {

FromArrayDisposable d = new FromArrayDisposable(s, array);

s.onSubscribe(d);

if (d.fusionMode) {

return;

}

d.run();

}

void run() {

T[] a = array;

int n = a.length;

for (int i = 0; i < n && !isDisposed(); i++) {

T value = a[i];

if (value == null) {

actual.onError(new NullPointerException("The " + i + "th element is null"));

return;

}

actual.onNext(value);

}

if (!isDisposed()) {

actual.onComplete();

}

}

看到这个for方法了吗 这个就是决定你跳过的数量的。

5filter

Paste_Image.png

这个相信大家很熟悉，对就是过滤

fromArray(1, 0, 6)

.filter(new Predicate() {

@Override

public boolean test(Integer integer) throws Exception {

return integer.intValue() > 5;

}

})

这里只是放出来关键代码

ObservableFilter的onNext

public void onNext(T t) {

if (sourceMode == NONE) {

boolean b;

try {

b = filter.test(t);

} catch (Throwable e) {

fail(e);

return;

}

if (b) {

actual.onNext(t);

}

} else {

actual.onNext(null);

}

}

这个b就是你的过滤条件。 下面的就是判断。 不符合的就不执行 actual.onNext(t);其实很简单的方式

6skip

和上面同理关键部分ObservableSkip的onNext方法

public void onNext(T t) {

if (remaining != 0L) {

remaining--;

} else {

actual.onNext(t);

}

}

7 scan

Paste_Image.png

RxJava的scan()函数可以看做是一个累加器函数。scan()函数对原始Observable发射的每一项数据都应用一个函数，它将函数的结果填充回可观测序列，等待和下一次发射的数据一起使用。

关键代码

@Override

public void onNext(T t) {

if (done) {

return;

}

final Observer super T> a = actual;

T v = value;

if (v == null) {

value = t;

a.onNext(t);

} else {

T u;

try {

u = ObjectHelper.requireNonNull(accumulator.apply(v, t), "The value returned by the accumulator is null");

} catch (Throwable e) {

Exceptions.throwIfFatal(e);

s.dispose();

onError(e);

return;

}

value = u;

a.onNext(u);

}

}

执行的时候value 会累加。 a.onNext(u);在发射出去

8 replay

PublishSubject source = PublishSubject.create();

ConnectableObservable connectableObservable = source.replay(2); // bufferSize = 3 to retain 3 values to replay

connectableObservable.connect(); // connecting the connectableObservable

connectableObservable.subscribe(getFirstObserver());

source.onNext(1);

source.onNext(2);

source.onNext(3);

source.onNext(4);

source.onComplete();

/*

* it will emit 2, 3, 4 as (count = 3), retains the 3 values for replay

*/

connectableObservable.subscribe(getSecondObserver());

replay 这个是缓存操作。

第二次订阅之后，就是缓存后面两个数据

9concat

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final String[] aStrings = {"A1", "A2", "A3", "A4"};

final String[] bStrings = {"B1", "B2", "B3"};

final Observable aObservable = Observable.fromArray(aStrings);

final Observable bObservable = Observable.fromArray(bStrings);

Observable.concat(aObservable, bObservable)

.subscribe(getObserver());

他的过程是

return RxJavaPlugins.onAssembly(new ObservableConcatMap(fromArray(sources), Functions.identity(), bufferSize(), ErrorMode.BOUNDARY));

concat操作符肯定也是有序的，实际上fromArray(sources)这么一个过程。

10merge

Paste_Image.png

final String[] aStrings = {"A1", "A2", "A3", "A4"};

final String[] bStrings = {"B1", "B2", "B3"};

final Observable aObservable = Observable.fromArray(aStrings);

final Observable bObservable = Observable.fromArray(bStrings);

Observable.merge(aObservable, bObservable)

.subscribe(getObserver());

无序的合并

11distinct 去除重复的

Paste_Image.png

enum HashSetCallable implements Callable> {

INSTANCE;

@Override

public Set call() throws Exception {

return new HashSet();

}

}

HashSet中 是不允许重复元素的

12last

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private void doSomeWork() {

getObservable().last("A1") // the default item ("A1") to emit if the source ObservableSource is empty

.subscribe(getObserver());

}

private Observable getObservable() {

return Observable.just("A1", "A2", "A3", "A4", "A5", "A6");

}

打印出来的是a6

ObservableFromArray的run方法

void run() {

T[] a = array;

int n = a.length;

for (int i = 0; i < n && !isDisposed(); i++) {

T value = a[i];

if (value == null) {

actual.onError(new NullPointerException("The " + i + "th element is null"));

return;

}

actual.onNext(value);

}

if (!isDisposed()) {

actual.onComplete();

}

}

ObservableLastSingle的onComplete

public void onComplete() {

s = DisposableHelper.DISPOSED;

T v = item;

if (v != null) {

item = null;

actual.onSuccess(v);

} else {

v = defaultItem;

if (v != null) {

actual.onSuccess(v);

} else {

actual.onError(new NoSuchElementException());

}

}

last方法会返回Single

13throttleFirst

Paste_Image.png

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 getObservable() {

return Observable.create(new ObservableOnSubscribe() {

@Override

public void subscribe(ObservableEmitter 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();

}

});

}

从这个可以理解到发送第一个之后。剩下的500之后才会接受第二个

14throttleLast

Paste_Image.png

从这个可以看出来，这是在一段时间内接受最后一个数据

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 getObservable() {

return Observable.create(new ObservableOnSubscribe() {

@Override

public void subscribe(ObservableEmitter 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();

}

});

}

15debounce

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 getObservable() {

return Observable.create(new ObservableOnSubscribe() {

@Override

public void subscribe(ObservableEmitter 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();

}

});

Paste_Image.png

这个接受的一一个时间跨度之内的数据

16window

Paste_Image.png

可以看出来大概 的意思就是截取被观察者组成一个新的被观察者

17delay

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