Example of how to swallow an error without ending the parent stream

rx-transformers-swallow-error.java

public static <T, R> Observable.Transformer<T, R> switchMapSwallowError(Func1<T, Observable<R>> onwardCall) {
  return new Observable.Transformer<T, R>() {

    private R previousValue = null;

    @Override
    public Observable<R> call(Observable<T> observable) {
      return observable.switchMap(
          a -> onwardCall.call(a)
              .doOnNext(value -> previousValue = value)
              .onErrorReturn(e -> previousValue)
      );
    }
  };
}
BehaviorSubject<Void> tigger = BehaviorSubject.create();
trigger.compose(switchMapSwallowError(aVoid->makeNetworkCall())).subscribe(next->{
},e->{})
tigger.onNext(null)//causes call to makeNetworkCall 
tigger.onNext(null)//causes call to makeNetworkCall which if it throws an error will return previous value
tigger.onNext(null)//causes call to makeNetworkCall