在RxJava中使用else语句

Question

The code below is simply checking null control and make mView.handleUrl(data) method work if all conditions are provided.

if( intent != null && intent.getExtras() != null ){
        String data = null;
        if( ( data = intent.getExtras().getString( AdvImagePagerFragment.ARG_PANAROMIC_IMAGE_DATA ) ) != null ){
            mView.handleUrl( data );
        }
    }

When I use code with RxJava I write code below.

 Single.just( intent )
                .filter( intent1 -> intent1 != null && intent1.getExtras() != null )
                .map( intent12 -> intent12.getExtras() )
                .filter( bundle -> bundle.getString( AdvImagePagerFragment.ARG_PANAROMIC_IMAGE_DATA  ) != null )
                .map( bundle -> bundle.getString( AdvImagePagerFragment.ARG_PANAROMIC_IMAGE_DATA ) )
                .subscribe( s -> mView.handleUrl( s ) );

Both code I write are working same. However the problem is starting when I try to add new condition to my code. For example, I can want to make some new operatins if the intent is null.

Example code;

if( intent != null && intent.getExtras() != null ){
        String data = null;
        if( ( data = intent.getExtras().getString( AdvImagePagerFragment.ARG_PANAROMIC_IMAGE_DATA ) ) != null ){
            mView.handleUrl( data );
        } else { // START Added a new condition
           mView.showError();
        }
    }

But I cannot write this code by using RxJava filter methods. As soon as filter return false, the operation is being completed. What is the solution in RxJava to add new conditions.

Answer 1

As a subscriber to that stream you are interested for 2 cases: if data is null and if data is not null. That means, that you cannot filter out the stream just like you have done previously.

    Single.just(sourceIntent)
            .map(intent -> {
                String data = "";
                Bundle bundle = intent.getExtras();
                if (bundle != null) {
                    data = bundle.getString(KEY, "");
                }
                return data;
            })
            .subscribe(data -> {
                if ("".equals(data)) view.showError();
                else view.handleUrl(data);
            });

Answer 2

Try this :-

Single.just( intent )
            .filter( intent1 -> intent1 != null && intent1.getExtras() != null )
            .map( intent12 -> intent12.getExtras() )
            .map( bundle -> bundle.getString( AdvImagePagerFragment.ARG_PANAROMIC_IMAGE_DATA ) )
            .map(string -> string == null ? "show_error" : string)
            .subscribe(new DisposableMaybeObserver<String>() {
                @Override
                public void onSuccess(String s) {

                }

                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onComplete() {

                }
            })

onNext(String s) {if (s.equalsIgnoreCase("show_error")) { //handle error }} like this:-

.subscribe(new DisposableMaybeObserver<String>() {
                @Override
                public void onSuccess(String s) {
                     if (s.equalsIgnoreCase("show_error")) {
                      //handle error 
                    mView.showError();
                    }
                    else
                     {
                           mView.handleUrl( data );
                        }
                }

                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onComplete() {

                }
            });

Hope this helps .

Answer 3

To split an observable into multiple observables based on some condition you should use groupBy operator .

Here is a nice example .

In your case you don't need it since you want to show an error and there is a separate mechanism for errors in Rx.

You can do something like:

Single.just( intent )
            .filter( intent1 -> intent1 != null && intent1.getExtras() != null )
            .map( intent12 -> intent12.getExtras() )
            .flatMap( bundle -> 
              String imageData = bundle.getString( AdvImagePagerFragment.ARG_PANAROMIC_IMAGE_DATA);
              if (imageData != null) {
                return Observanle.just(imageData); 
              } else {
                return Observable.error(new RuntimeException("something is wrong));
              }
            ).subscribe(s -> mView.handleUrl( s ),
                        error -> mView.showError( error ));