RxJava 基礎用法案例分享原始碼解析【附程式碼】-java教程-PHP中文網

本文詳述RxJava的基礎用法， RxJava是一個用法很簡單的神奇框架,但內部實作有點複雜,程式碼邏輯有點繞。網路上關於RxJava源碼分析的文章,源碼貼很少且不全，下面羅列了完整的源碼解析，供參考。

1.RxJava 基礎用法

Observable.create(new Observable.OnSubscribe () { @Override public void call(Subscriber subscriber) { } }).subscribe(new Observer () { @Override public void onCompleted() {

}

@Override public void onError(Throwable e) {

}

@Override public void onNext(Object o) {

} }); 登入後複製 2.先看 .subscribe(new Observer () )這個方法

public final Subscription subscribe(final Observer observer) { if (observer instanceof Subscriber) { return subscribe((Subscriber )observer); } if (observer == null) { throw new NullPointerException("observer is null"); } return subscribe(new ObserverSubscriber (observer)); } 登入後複製 這裡只是將傳進來的observer 參數參數進行了簡單的封裝（ObserverableSubscriber）

繼續看subscribe 方法

public final Subscription subscribe(Subscriber subscriber) { return Observable.subscribe(subscriber, this); } 登入後複製 static Subscription subscribe(Subscriber subscriber, Observable observable) { // validate and proceed if (subscriber == null) { throw new IllegalArgumentException("subscriber can not be null"); } if (observable.onSubscribe == null) { throw new IllegalStateException("onSubscribe function can not be null."); /* * the subscribe function can also be overridden but generally that's not the appropriate approach * so I won't mention that in the exception */ }

// new Subscriber so onStart it subscriber.onStart();

/* * See https://github.com/ReactiveX/RxJava/issues/216 for discussion on "Guideline 6.4: Protect calls * to user code from within an Observer" */ // if not already wrapped if (!(subscriber instanceof SafeSubscriber)) { // assign to `observer` so we return the protected version subscriber = new SafeSubscriber (subscriber); }

// The code below is exactly the same an unsafeSubscribe but not used because it would // add a significant depth to already huge call stacks. try { // allow the hook to intercept and/or decorate RxJavaHooks.onObservableStart(observable, observable.onSubscribe).call(subscriber); return RxJavaHooks.onObservableReturn(subscriber); } catch (Throwable e) { // special handling for certain Throwable/Error/Exception types Exceptions.throwIfFatal(e); // in case the subscriber can't listen to exceptions anymore if (subscriber.isUnsubscribed()) { RxJavaHooks.onError(RxJavaHooks.onObservableError(e)); } else { // if an unhandled error occurs executing the onSubscribe we will propagate it try { subscriber.onError(RxJavaHooks.onObservableError(e)); } catch (Throwable e2) { Exceptions.throwIfFatal(e2); // if this happens it means the onError itself failed (perhaps an invalid function implementation) // so we are unable to propagate the error correctly and will just throw RuntimeException r = new OnErrorFailedException("Error occurred attempting to subscribe [" + e.getMessage() + "] and then again while trying to pass to onError.", e2); // TODO could the hook be the cause of the error in the on error handling. RxJavaHooks.onObservableError(r); // TODO why aren't we throwing the hook's return value. throw r; // NOPMD } } return Subscriptions.unsubscribed(); } } 登入後複製 這裡面只需要注意

RxJavaHooks.onObservableStart(observable, observable.onSubscribe).call(subscriber); 登入後複製 public static Observable.OnSubscribe onObservableStart(Observable instance, Observable.OnSubscribe onSubscribe) { Func2 f = onObservableStart; if (f != null) { return f.call(instance, onSubscribe); } return onSubscribe; } 登入後複製 RxJavaHooks.onObservableStart(observable, observable.onSubscribe) 这个方法返回的是它的第二个参数，也就是Observable它自己的onSubscribe 对象， 所以在subscribe 方法里面调用了 onSubscribe.call(subscriber)方法 登入後複製 這裡的subscriber 就是傳進來的參數

protected Observable(OnSubscribe f) { this.onSubscribe = f; } 登入後複製 public static Observable create(OnSubscribe f) { return new Observable (RxJavaHooks.onCreate(f)); } 登入後複製 ##可以看出onSubscribe 物件 是create 傳進來的參數，那麼整個流程就很清楚了

只有呼叫了subscribe 方法整個流程才會執行：subscribe ===>呼叫 onSubscribe.call(observer ) 方法 同時也把observer 傳遞進去了

RxJava 基礎用法案例分享原始碼解析【附程式碼】

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