title: EditText validation on ViewModel using RxJava2
body: <p>I'm trying to use RxJava to perform a validation on a EditText when I click a button but I'm having a hard time moving the validation to the ViewModel which would make testing much easier. I'm using RxBindings from Jake Wharton to get the UI input and RxJava2's Flowable.combineLatest with a PublishSubject to trigger the Flowable when I click a button on a AlertDialog. Here's what I got so far:</p>
  
  <pre><code>private Flowable&lt;CharSequence&gt; projectTitleObservable;
  private final PublishSubject&lt;CharSequence&gt; createProjectClicked = PublishSubject.create();
  
  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
      final Context context = getActivity();
  
      View dialogView = LayoutInflater.from(context).inflate(R.layout.new_project, null);
  
      ButterKnife.bind(this, dialogView);
  
      projectTitleObservable = RxTextView.textChanges(projectNameEditText).toFlowable(BackpressureStrategy.LATEST);
  
      ConnectableFlowable &lt;CharSequence&gt; connectableFlowable = Flowable.combineLatest(createProjectClicked.toFlowable(BackpressureStrategy.LATEST), projectTitleObservable, (ignored, title) -&gt; {
          boolean validTitle = !TextUtils.isEmpty(title);
          if (!validTitle) {
              projectNameEditText.setError("Project must have a name");
          }
  
          Timber.d("Hey, lambdas work! Look -&gt; " + title);
          return title;
      })
              .publish();
  
      connectableFlowable.subscribe(test -&gt; Timber.d(test.toString()));
  
      return new AlertDialog.Builder(context)
              .setTitle("Add new Project")
              .setView(dialogView)
              .setPositiveButton(android.R.string.ok, (dialogInterface, i) -&gt; {
                  Timber.d("Ok clicked!");
                  createProjectClicked.onNext("It works!");
              })
              .setNegativeButton(android.R.string.cancel, (dialogInterface, i) -&gt; Timber.d("Cancel clicked!"))
              .create();
  }
  </code></pre>
  
  <p>I'm only publishing and subscribing on the same place to make sure it actually works before moving the ConnectableFlowable to the ViewModel. The only log I got was the "Ok clicked!" which for me it means it was never subscribed. Any idea on why it's not subscribing?</p>