RxJava 2.x 源码分析（二） 线程切换原理

在RxJava的使用过程中，通常会用subscribeOn来指定可观察者Observable的线程，用observerOn来指定观察者Observer的线程。本文将分析RxJava2.x的线程切换原理

先来看一个例子

Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(@NonNull ObservableEmitter<Integer> e) throws Exception {
                mRxOperatorsText.append("Observable emit 1" + "\n");
                Log.d(TAG, "Observable emit 1" + "\n");
                e.onNext(1);
                mRxOperatorsText.append("Observable emit 2" + "\n");
                Log.d(TAG, "Observable emit 2" + "\n");
                e.onNext(2);
                mRxOperatorsText.append("Observable emit 3" + "\n");
                Log.d(TAG, "Observable emit 3" + "\n");
                e.onNext(3);
                //e.onComplete();
                mRxOperatorsText.append("Observable emit 4" + "\n");
                Log.d(TAG, "Observable emit 4" + "\n" );
                e.onNext(4);
                Log.d(TAG, "subscribe: ThreadName="+Thread.currentThread().getName());
            }
        }).subscribeOn(Schedulers.io()) //将发射者切换到io线程
                .observeOn(AndroidSchedulers.mainThread()) //将接收者切换到主线程
                .subscribe(new Observer<Integer>() {
            private int i;
            private Disposable mDisposable;

            @Override
            public void onSubscribe(@NonNull Disposable d) {
                mRxOperatorsText.append("onSubscribe : " + d.isDisposed() + "\n");
                Log.d(TAG, "onSubscribe : " + d.isDisposed() + "\n" );
                mDisposable = d;
                Log.d(TAG, "onSubscribe: ThreadName="+Thread.currentThread().getName());
            }

            @Override
            public void onNext(@NonNull Integer integer) {
                mRxOperatorsText.append("onNext : value : " + integer + "\n");
                Log.d(TAG, "onNext : value : " + integer + "\n" );
                Log.d(TAG, "onNext: ThreadName="+Thread.currentThread().getName());
                i++;
                if (i == 2) {
                    // 在RxJava 2.x 中，新增的Disposable可以做到切断的操作，让Observer观察者不再接收上游事件
                    mDisposable.dispose();
                    mRxOperatorsText.append("onNext : isDisposable : " + mDisposable.isDisposed() + "\n");
                    Log.d(TAG, "onNext : isDisposable : " + mDisposable.isDisposed() + "\n");
                }
            }

            @Override
            public void onError(@NonNull Throwable e) {
                mRxOperatorsText.append("onError : value : " + e.getMessage() + "\n");
                Log.d(TAG, "on