讀了RxJava系列(一)的童鞋們,應(yīng)該大致明白了Rxjava的普遍寫法是做什么的了,但是真正的Rxjava的內(nèi)部結(jié)構(gòu)呢?
常見的Rxjava代碼形式:
Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(ObservableEmitter<String> emitter) throws Exception {
emitter.onNext("1");
emitter.onNext("2");
emitter.onNext("3");
emitter.onComplete();
}
}).subscribe(new Observer<String>() {
@Override
public void onSubscribe(Disposable d) {
}
@Override
public void onNext(String s) {
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
}
});
代碼分析:
Observable.create
public static <T> Observable<T> create(ObservableOnSubscribe<T> source) {
ObjectHelper.requireNonNull(source, "source is null");
return RxJavaPlugins.onAssembly(new ObservableCreate<T>(source));
}
通過new ObservableCreate<T>(source)可以知道實(shí)際上就是new了一個ObservableCreate類,ObservableCreate的結(jié)構(gòu):
public final class ObservableCreate<T> extends Observable<T> {
final ObservableOnSubscribe<T> source;
public ObservableCreate(ObservableOnSubscribe<T> source) {
this.source = source;
}
@Override
protected void subscribeActual(Observer<? super T> observer) {
CreateEmitter<T> parent = new CreateEmitter<T>(observer);
observer.onSubscribe(parent);
try {
source.subscribe(parent);
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
parent.onError(ex);
}
}
static final class CreateEmitter<T>
extends AtomicReference<Disposable>
implements ObservableEmitter<T>, Disposable {
private static final long serialVersionUID = -3434801548987643227L;
final Observer<? super T> observer;
CreateEmitter(Observer<? super T> observer) {
this.observer = observer;
}
@Override
public void onNext(T t) {
只截取了重要的部分,可以看到subscribeActual方法中調(diào)用了source.subscribe(parent)方法,但是subscribeActual方法又是誰調(diào)用的呢?
.subscribe
public final void subscribe(Observer<? super T> observer) {
ObjectHelper.requireNonNull(observer, "observer is null");
try {
observer = RxJavaPlugins.onSubscribe(this, observer);
ObjectHelper.requireNonNull(observer, "The RxJavaPlugins.onSubscribe hook returned a null Observer. Please change the handler provided to RxJavaPlugins.setOnObservableSubscribe for invalid null returns. Further reading: https://github.com/ReactiveX/RxJava/wiki/Plugins");
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;
}
}
可以看到在調(diào)用訂閱方法的時候,調(diào)用了subscribeActual方法,
source.subscribe(parent);
然后下游在onNext,onError,onComplete中就獲取到了數(shù)據(jù)
static final class CreateEmitter<T>
extends AtomicReference<Disposable>
implements ObservableEmitter<T>, Disposable {
private static final long serialVersionUID = -3434801548987643227L;
final Observer<? super T> observer;
CreateEmitter(Observer<? super T> observer) {
this.observer = observer;
}
@Override
public void onNext(T t) {
if (t == null) {
onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
return;
}
if (!isDisposed()) {
observer.onNext(t);
}
}
@Override
public void onError(Throwable t) {
if (!tryOnError(t)) {
RxJavaPlugins.onError(t);
}
}
@Override
public boolean tryOnError(Throwable t) {
if (t == null) {
t = new NullPointerException("onError called with null. Null values are generally not allowed in 2.x operators and sources.");
}
if (!isDisposed()) {
try {
observer.onError(t);
} finally {
dispose();
}
return true;
}
return false;
}
@Override
public void onComplete() {
if (!isDisposed()) {
try {
observer.onComplete();
} finally {
dispose();
}
}
}
@Override
public void setDisposable(Disposable d) {
DisposableHelper.set(this, d);
}
@Override
public void setCancellable(Cancellable c) {
setDisposable(new CancellableDisposable(c));
}
@Override
public ObservableEmitter<T> serialize() {
return new SerializedEmitter<T>(this);
}
@Override
public void dispose() {
DisposableHelper.dispose(this);
}
@Override
public boolean isDisposed() {
return DisposableHelper.isDisposed(get());
}
@Override
public String toString() {
return String.format("%s{%s}", getClass().getSimpleName(), super.toString());
}
}
同時下游通過Disposable 中dispose方法,來決定之后的數(shù)據(jù)要不要發(fā)送到下游.
總結(jié):
1>new一個匿名類ObservableCreate,重寫了subscribe這個方法,然后該類的構(gòu)造函數(shù)需要ObservableOnSubscribe接口
2>調(diào)用該類實(shí)現(xiàn)的父類的方法subscribe來調(diào)用subscribeActual,進(jìn)而調(diào)用observer.onSubscribe(parent)與匿名類ObservableCreate的subscribe方法
小記:本來是打算寫的詳細(xì)一點(diǎn),但是發(fā)現(xiàn)本身很簡單.....
