使用RxJava时，有时会出现：io.reactivex.exceptions.UndeliverableException异常。
出现这个异常的原因大概是：调用了多次onError。正常来说第一次onError会走正常Observer处理，其他的会走ErrorHandler。可以通过如下方法捕捉多次的error，此方法只需要在Application中执行一次即可。

private void setRxJavaErrorHandler() {
    RxJavaPlugins.setErrorHandler(new Consumer<Throwable>() {
        @Override
        public void accept(Throwable e) {
            if (e instanceof UndeliverableException) {
                e = e.getCause();
                Log.d(TAG, "UndeliverableException=" + e);
                return;
            } else if ((e instanceof IOException)) {
                // fine, irrelevant network problem or API that throws on cancellation
                return;
            } else if (e instanceof InterruptedException) {
                // fine, some blocking code was interrupted by a dispose call
                return;
            } else if ((e instanceof NullPointerException) || (e instanceof IllegalArgumentException)) {
                // that's likely a bug in the application
                Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
                return;
            } else if (e instanceof IllegalStateException) {
                // that's a bug in RxJava or in a custom operator
                Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
                return;
            }
            Log.d(TAG, "unknown exception=" + e);
        }
    });
}