出現異常：io.reactivex.exceptions.UndeliverableException
出現原因：呼叫了多次onError，正常來說，出現一次onError會走正常Observer處理，其他的會走Error handling ,可以通過以下捕捉多次的error：

RxJavaPlugins.setErrorHandler(new Consumer<Throwable>() {
            @Override
            public void accept(Throwable e) {
                if (e instanceof
 
 UndeliverableException) {
                    e = e.getCause();
                }
                if ((e instanceof IOException)) {
                    // fine, irrelevant network problem or API that throws on cancellation
                    return;
                }
                if (e instanceof
 
 InterruptedException) {
                    // fine, some blocking code was interrupted by a dispose call
                    return;
                }
                if ((e instanceof NullPointerException) || (e instanceof IllegalArgumentException)) {
                    // that's likely a bug in the application
 

                    Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
                    return;
                }
                if (e instanceof IllegalStateException) {
                    // that's a bug in RxJava or in a custom operator
                    Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
                    return;
                }
                Logger.l("Undeliverable exception");
            }
        });