Rxjava源码解析--observeOn指定线程

基于rxjava1.1.0 rxandroid 1.0.1

用例代码↓
        Observable observable1 = Observable.create(new Observable.OnSubscribe() {
            public void call(Subscriber subscriber) {
                subscriber.onNext("1");
                subscriber.onCompleted();
            }
        });

        Subscriber subscriber1 = new Subscriber() {
            @Override
            public void onCompleted() {
            }

            @Override
            public void onError(Throwable e) {
            }

            @Override
            public void onNext(String s) {
                Log.e("haha",s);
            }
        };
 observable1.observeOn(AndroidSchedulers.mainThread()).subscribe(subscriber1);

observeOn源码精简↓
public final Observable observeOn(Scheduler scheduler) {
        return lift(new OperatorObserveOn(scheduler));
    }

AndroidSchedulers 源码↓
public final class AndroidSchedulers {
    private AndroidSchedulers() {
        throw new AssertionError("No instances");
    }

    private static final Scheduler MAIN_THREAD_SCHEDULER =
            new HandlerScheduler(new Handler(Looper.getMainLooper()));

    ①
    public static Scheduler mainThread() {
        Scheduler scheduler =
                RxAndroidPlugins.getInstance().getSchedulersHook().getMainThreadScheduler();
        return scheduler != null ? scheduler : MAIN_THREAD_SCHEDULER;
    }
}

lift精简源码↓
public final  Observable lift(final Operator operator) {
        ②
        //create Observable2  OnSubscribe2
        return new Observable(new OnSubscribe() {
            ③
            @Override
            public void call(Subscriber o) {
                Subscriber st = hook.onLift(operator).call(o);
                st.onStart();
                ⑤
                onSubscribe.call(st);//onSubscribe1.call(subscriber2)
            }
        });
    }

OperatorObserveOn源码片段↓
    ④
    @Override
    public Subscriber call(Subscriber child) {//child = subscriber1
        if (scheduler instanceof ImmediateScheduler) {
            // avoid overhead, execute directly
            return child;
        } else if (scheduler instanceof TrampolineScheduler) {
            // avoid overhead, execute directly
            return child;
        } else {
            ObserveOnSubscriber parent = new ObserveOnSubscriber(scheduler, child);
            parent.init();
            return parent;
        }
    }

        ⑥
        @Override
        public void onNext(final T t) {
            if (isUnsubscribed()) {
                return;
            }
            ⑦
            if (!queue.offer(on.next(t))) {
                onError(new MissingBackpressureException());
                return;
            }
            schedule();
        }

final Action0 action = new Action0() {
            @Override
            public void call() {
                pollQueue();
            }
        };

        protected void schedule() {
            if (counter.getAndIncrement() == 0) {
                recursiveScheduler.schedule(action);
            }
        }

pollQueue精简版↓
void pollQueue() {
        Object o = queue.poll();
        if (o != null) {
            ⑧
            child.onNext(on.getValue(o));
        } else {
            break;
        }
    }

OperatorObserveOn.ObserveOnSubscriber源码片段↓
public ObserveOnSubscriber(Scheduler scheduler, Subscriber child) {
            this.child = child;
            this.recursiveScheduler = scheduler.createWorker();
            if (UnsafeAccess.isUnsafeAvailable()) {
                queue = new SpscArrayQueue