RxDogTag是一个用于标记RxJava2观察者中的原始订阅点的实用程序，其目标是在出现未处理错误的情况下显示其订阅位置以便稍后进行错误报告/调查。这仅适用于未实现onError（）的RxJava观察者。
请看如下经典的RxJava错误：
Observable.range(0,10).subscribeOn(Schedulers.io()).map(i->null).subscribe();这是RxJava并发中非常常见的问题，没有标识的话，会产生如下的异常信息：
io.reactivex.exceptions.OnErrorNotImplementedException:TheexceptionwasnothandledduetomissingonErrorhandlerinthesubscribe()methodcall.Furtherreading:https://github.com/ReactiveX/RxJava/wiki/Error-Handling|Themapperfunctionreturnedanullvalue.atio.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)atio.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)atio.reactivex.internal.observers.LambdaObserver.onError(LambdaObserver.java:77)atio.reactivex.internal.observers.BasicFuseableObserver.onError(BasicFuseableObserver.java:100)atio.reactivex.internal.observers.BasicFuseableObserver.fail(BasicFuseableObserver.java:110)atio.reactivex.internal.operators.observable.ObservableMap$MapObserver.onNext(ObservableMap.java:59)atio.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeOnObserver.onNext(ObservableSubscribeOn.java:58)atio.reactivex.internal.operators.observable.ObservableScalarXMap$ScalarDisposable.run(ObservableScalarXMap.java:248)atio.reactivex.internal.operators.observable.ObservableJust.subscribeActual(ObservableJust.java:35)atio.reactivex.Observable.subscribe(Observable.java:12090)atio.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeTask.run(ObservableSubscribeOn.java:96)atio.reactivex.Scheduler$DisposeTask.run(Scheduler.java:578)atio.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:66)atio.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:57)atjava.util.concurrent.FutureTask.run(FutureTask.java:266)atjava.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)atjava.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)atjava.lang.Thread.run(Thread.java:748)Causedby:java.lang.NullPointerException:Themapperfunctionreturnedanullvalue.atio.reactivex.internal.functions.ObjectHelper.requireNonNull(ObjectHelper.java:39)atio.reactivex.internal.operators.observable.ObservableMap$MapObserver.onNext(ObservableMap.java:57)...14more你很难从这份报告中清楚的了解实际的状况。
而启用了RxDogTag后，相同的错误变成：
io.reactivex.exceptions.OnErrorNotImplementedException:Themapperfunctionreturnedanullvalue.Causedby:java.lang.NullPointerException:Themapperfunctionreturnedanullvalue.at[[Inferredsubscribepoint]].(:0)atcom.uber.anotherpackage.ReadMeExample.complex(ReadMeExample.java:55)at[[Originaltrace]].(:0)atio.reactivex.internal.functions.ObjectHelper.requireNonNull(ObjectHelper.java:39)atio.reactivex.internal.operators.observable.ObservableMap$MapObserver.onNext(ObservableMap.java:57)atio.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeOnObserver.onNext(ObservableSubscribeOn.java:58)atio.reactivex.internal.operators.observable.ObservableScalarXMap$ScalarDisposable.run(ObservableScalarXMap.java:248)atio.reactivex.internal.operators.observable.ObservableJust.subscribeActual(ObservableJust.java:35)atio.reactivex.Observable.subscribe(Observable.java:12090)atio.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeTask.run(ObservableSubscribeOn.java:96)atio.reactivex.Scheduler$DisposeTask.run(Scheduler.java:578)atio.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:66)atio.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:57)atjava.util.concurrent.FutureTask.run(FutureTask.java:266)atjava.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)atjava.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)atjava.lang.Thread.run(Thread.java:748)这样我们就知道这个错误对应的代码是 ReadMeExample.java:55.这并非找出问题根源的银弹，但至少你知道错误在哪里。
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