RxJava2.0 操作符之 -- 异常操作符

onErrorReturn

让 Observable 遇到错误时发射一个特殊的项并且正常终止

Observable.create(new ObservableOnSubscribe() {
    public void subscribe(@NonNull ObservableEmitter e) throws Exception {
            e.onNext(1);

 throw new RuntimeException("error");

  }
}).onErrorReturn(new Function, Integer>() {
    public Integer apply(@NonNull Throwable throwable) throws Exception {
        return 5;
  }
}).subscribe(RxUtils.getObserver());
​

	onSubscribe
	Thread:Thread[main,5,main]
	onNext:1
	Thread:Thread[main,5,main]
	onNext:5
	Thread:Thread[main,5,main]
	onComplete
	Thread:Thread[main,5,main]
​

onErrorResumeNext

让 Observable 在遇到错误时开始发射第二个 Observable 的数据序列。

	Observable.create(new ObservableOnSubscribe() {
		public void subscribe(@NonNull ObservableEmitter e) throws Exception {
			e.onNext(3);
	 throw new RuntimeException("error");
	  }
	}).onErrorResumeNext(new Function, ObservableSourceextends Integer>>() {
		public ObservableSourceextends Integer> apply(@NonNull Throwable throwable) throws Exception {
			return Observable.just(5,6,7);
	  }
	}).subscribe(RxUtils.getObserver());
​

	onSubscribe
	Thread:Thread[main,5,main]
	onNext:3
	Thread:Thread[main,5,main]
	onNext:5
	Thread:Thread[main,5,main]
	onNext:6
	Thread:Thread[main,5,main]
	onNext:7
	Thread:Thread[main,5,main]
	onComplete
	Thread:Thread[main,5,main]
​

onExceptionResumeNext

和 onErrorResumeNext 类似，onExceptionResumeNext 方法返回一个镜像原有 Observable 行为的新 Observable，也使用一个备用的 Observable，不同的是，如果 onError 收到的 Throwable 不是## 一个 Exception，它会将错误传递给观察者的 onError 方法，不会使用备用的 Observable。

Observable.create(new ObservableOnSubscribe() {
    public void subscribe(@NonNull ObservableEmitter e) throws Exception {
        e.onNext(3);
 throw new RuntimeException("error");
  }
}).onExceptionResumeNext(Observable.just(5,6,7)).subscribe(RxUtils.getObserver());
​

onSubscribe
Thread:Thread[main,5,main]
onNext:3
Thread:Thread[main,5,main]
onNext:5
Thread:Thread[main,5,main]
onNext:6
Thread:Thread[main,5,main]
onNext:7
Thread:Thread[main,5,main]
onComplete
Thread:Thread[main,5,main]
​

retry

如果原始 Observable 遇到错误，重新订阅它期望它能正常终止

Observable.create(new ObservableOnSubscribe() {
    public void subscribe(@NonNull ObservableEmitter e) throws Exception {
        try {
            for (int i = 0; i < 10; i++) {
                if (i == 4) {
                    throw new Exception(
                            "this is number 4 error！");
  }
                e.onNext(i);
  }
            e.onComplete();
  } catch (Throwable ex) {
            e.onError(ex);
  }
    }
}).retry(2).subscribe(RxUtils.getObserver());
​

onSubscribe
Thread:Thread[main,5,main]
onNext:0
Thread:Thread[main,5,main]
onNext:1
Thread:Thread[main,5,main]
onNext:2
Thread:Thread[main,5,main]
onNext:3
Thread:Thread[main,5,main]
onNext:0
Thread:Thread[main,5,main]
onNext:1
Thread:Thread[main,5,main]
onNext:2
Thread:Thread[main,5,main]
onNext:3
Thread:Thread[main,5,main]
onNext:0
Thread:Thread[main,5,main]
onNext:1
Thread:Thread[main,5,main]
onNext:2
Thread:Thread[main,5,main]
onNext:3
Thread:Thread[main,5,main]
onError:java.lang.Exception: this is number 4 error！
Thread:Thread[main,5,main]
​

retryWhen

retryWhen 和 retry 类似，区别是，retryWhen 将 onError 中的 Throwable 传递给一个函数，这个函数产生另一个 Observable，retryWhen 观察它的结果再决定是不是要重新订阅原始的

Observable。如果这个 Observable 发射了一项数据，它就重新订阅，如果这个 Observable 发射的是 onError 通知，它就将这个通知传递给观察者然后终止。

Observable.create(new ObservableOnSubscribe() {
    public void subscribe(@NonNull ObservableEmitter e) throws Exception {
        try {
            for (int i = 0; i < 10; i++) {
                if (i == 4) {
                    throw new Exception(
                            "this is number 4 error！");
  }
                e.onNext(i);
  }
            e.onComplete();
  } catch (Throwable ex) {
            e.onError(ex);
  }
    }
}).retryWhen(new Function, ObservableSource>() {
       public ObservableSource apply(@NonNull Observable throwableObservable) throws Exception {
           return Observable.just(12,13);
  }
   }).subscribe(RxUtils.getObserver());
 try {
        Thread.sleep(Integer.MAX_VALUE);
  } catch (InterruptedException e1) {
        // TODO Auto-generated catch block
  e1.printStackTrace();
  }
​

onSubscribe
Thread:Thread[main,5,main]
onNext:0
Thread:Thread[main,5,main]
onNext:1
Thread:Thread[main,5,main]
onNext:2
Thread:Thread[main,5,main]
onNext:3
Thread:Thread[main,5,main]
onNext:0
Thread:Thread[main,5,main]
onNext:1
Thread:Thread[main,5,main]
onNext:2
Thread:Thread[main,5,main]
onNext:3
Thread:Thread[main,5,main]
onComplete
Thread:Thread[main,5,main]

Process finished with exit code 1

​