代碼一：
observable.subscribeOn(Schedulers.io())
.map(new ResultFunc<Observable>())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(spSubscriber);
map會調用以下方法，mapper參數就是new ResultFunc<Observable>(),RxJavaPlugins.onAssembly(new ObservableMap<T, R>(this, mapper))這句話中的this,就是代碼一中的observablesubscribeOn,
代碼二 ：
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public final <R> Observable<R> map(Function<? super T, ? extends R> mapper) {
ObjectHelper.requireNonNull(mapper, "mapper is null");
return RxJavaPlugins.onAssembly(new ObservableMap<T, R>(this, mapper));
}
把this,對象保存爲source,並註冊了function函數
代碼三：
public ObservableMap(ObservableSource<T> source, Function<? super T, ? extends U> function) {
super(source);
this.function = function;
}
然後執行代碼一中的subscribe方法，進行觀察者註冊,
代碼四：在subscribe方法中會調用subscribeActual(observer)方法，這個方法是父類的抽象方法，因爲當前的子類爲ObservableMap,所以會去調用
代碼五
@SchedulerSupport(SchedulerSupport.NONE)
@Override
public final void subscribe(Observer<? super T> observer) {
ObjectHelper.requireNonNull(observer, "observer is null");
try {
observer = RxJavaPlugins.onSubscribe(this, observer);
ObjectHelper.requireNonNull(observer, "Plugin returned null Observer");
subscribeActual(observer);
} catch (NullPointerException e) { // NOPMD
throw e;
} catch (Throwable e) {
Exceptions.throwIfFatal(e);
// can't call onError because no way to know if a Disposable has been set or not
// can't call onSubscribe because the call might have set a Subscription already
RxJavaPlugins.onError(e);
NullPointerException npe = new NullPointerException("Actually not, but can't throw other exceptions due to RS");
npe.initCause(e);
throw npe;
}
}
在代碼五中，source會去註冊source的subscribe,因爲代碼四中的subscribe是ObservableMap的(這個地方有疑問),這個source就是代碼一中的observable,這樣子就把代碼五中包裝一層new MapObserver<T, U>(t, function)的又成功註冊給了source,當source發出onNext時，就會先觸發MapObserver的onNext
代碼五：
@Override
public void subscribeActual(Observer<? super U> t) {
source.subscribe(new MapObserver<T, U>(t, function));
}
在MapObserver的onNext方法中會去調用轉換方法mapper.apply(t),並且把轉換後的結果v返回,最後在調用代碼一中的 spSubscriber方法，實現了結果調用。
代碼六：
@Override
public void onNext(T t) {
if (done) {
return;
}
if (sourceMode != NONE) {
actual.onNext(null);
return;
}
U v;
try {
v = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper function returned a null value.");
} catch (Throwable ex) {
fail(ex);
return;
}
actual.onNext(v);
}
完。