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转换相关的操作符 以及 官方介绍
RxJava 之 flatMap 系列 转换操作符 官方介绍 ：Transforming Observables
flatMapflatMapCompletableflatMapIterableflatMapMaybeflatMapObservableflatMapPublisherflatMapSingleflatMapSingleElement
以下介绍我们就直接具体实现，中间流程请参考 RxJava之create操作符源码解析。
flatMap
- 官方示例：
输出：Observable.just("A", "B", "C") .flatMap(new Function(A, 1) (B, 1) (C, 1) (C, 2) (B, 2) (A, 2) (A, 3) (B, 3) (C, 3) - 返回对象的
ObservableFlatMap的subscribeActual方法：public void subscribeActual(Observer t) { if (ObservableScalarXMap.tryScalarXMapSubscribe(source, t, mapper)) { return; } source.subscribe(new MergeObserver -
MergeObserver的onNext方法：public void onNext(T t) { // safeguard against misbehaving sources ... subscribeInner(p); } void subscribeInner(ObservableSource p) { for (;;) { if (p instanceof Callable) { ... drain(); ... } else { InnerObserver -
InnerObserver的onNext方法：public void onNext(U t) { if (fusionMode == QueueDisposable.NONE) { parent.tryEmit(t, this); } else { parent.drain(); } } -
MergeObserver的drain()方法：
最终还是调用了 传进来的void drain() { if (getAndIncrement() == 0) { drainLoop(); } } void drainLoop() { final Observer child = this.downstream;//1.0 int missed = 1; for (;;) { ... SimplePlainQueue svq = queue; if (svq != null) { for (;;) { ... U o = svq.poll(); if (o == null) { break; } child.onNext(o);//1.1 } } ... if (d && (svq == null || svq.isEmpty()) && n == 0 && nSources == 0) { Throwable ex = errors.terminate(); if (ex != ExceptionHelper.TERMINATED) { if (ex == null) { child.onComplete();//1.2 } else { child.onError(ex);//1.3 } } return; } ... } }observer的 对应方法。
flatMapCompletable
官方示例：
Observable source = Observable.just(2, 1, 3);
Completable completable = source.flatMapCompletable(new Function() {
@Override
public CompletableSource apply(final Integer x) throws Exception {
return Completable.timer(x, TimeUnit.SECONDS)
.doOnComplete(new Action() {
@Override
public void run() throws Exception {
System.out.println("Info: Processing of item \"" + x + "\" completed");
}
});
}
});
completable.doOnComplete(
new Action() {
@Override
public void run() throws Exception {
System.out.println("Info: Processing of all items completed");
}
})
.blockingAwait();
输出：
Info: Processing of item "1" completed
Info: Processing of item "2" completed
Info: Processing of item "3" completed
Info: Processing of all items completed
flatMapIterable
官方示例：
Observable.just(1, 2, 3, 4)
.flatMapIterable(new Function>() {
@Override
public Iterable apply(Integer integer) throws Exception {
switch (integer % 4) {
case 1:
return Arrays.asList("A");
case 2:
return Arrays.asList("B", "B");
case 3:
return Arrays.asList("C", "C", "C");
default:
return Arrays.asList();
}
}
})
.subscribe(new Consumer 输出：
A
B
B
C
C
C
flatMapMaybe
官方示例：
Observable.just(9.0, 16.0, -4.0)
.flatMapMaybe(new Function>() {
@Override
public MaybeSource apply(Double x) throws Exception {
if (x.compareTo(0.0) < 0) {
return Maybe.empty();
} else {
return Maybe.just(Math.sqrt(x));
}
}
})
.subscribe(new Observer 输出：
3.0
4.0
onComplete
flatMapObservable
官方示例：
Single source = Single.just("Kirk, Spock, Chekov, Sulu");
Observable names = source.flatMapObservable(new Function>() {
@Override
public ObservableSource apply(String text) throws Exception {
return Observable.fromArray(text.split(","))
.map(new Function() {
@Override
public String apply(String s) throws Exception {
return s;
}
});
}
});
names.subscribe(new Consumer() {
@Override
public void accept(String name) throws Exception {
System.out.println("onNext: " + name);
}
});
输出：
onNext: Kirk
onNext: Spock
onNext: Chekov
onNext: Sulu
flatMapPublisher
官方示例：
Single source = Single.just("Kirk, Spock, Chekov, Sulu");
Flowable names = source.flatMapPublisher(new Function>() {
@Override
public Publisher apply(String text) throws Exception {
return Flowable.fromArray(text.split(","))
.map(new Function() {
@Override
public String apply(String s) throws Exception {
return s;
}
});
}
});
names.subscribe(new Consumer() {
@Override
public void accept(String name) throws Exception {
System.out.println("onNext: " + name);
}
});
输出：
onNext: Kirk
onNext: Spock
onNext: Chekov
onNext: Sulu
flatMapSingle
官方示例：
Observable.just(4, 2, 1, 3)
.flatMapSingle(new Function>() {
@Override
public SingleSource apply(final Integer integer) throws Exception {
return Single.timer(integer, TimeUnit.SECONDS)
.map(new Function() {
@Override
public Object apply(Long aLong) throws Exception {
return integer;
}
});
}
})
.blockingSubscribe(new Consumer 输出：
1
2
3
4
flatMapSingleElement
官方示例：
Maybe source = Maybe.just(-42);
Maybe result = source.flatMapSingleElement(new Function>() {
@Override
public SingleSource apply(Integer x) throws Exception {
return Single.just(Math.abs(x));
}
});
result.subscribe(new Consumer() {
@Override
public void accept(Integer integer) throws Exception {
System.out.println(integer);
}
});
输出：
42
以上