ViewObservable.text() does not work with Observable.delay()

[ronshapiro]

I think I was a little too optimistic when I wrote ViewObservable.text() to emit the view itself, because it doesn't capture any value in it's original state, which is problematic when using transformations like .delay(). Here's one example:

ViewObservable.text(myTextView)
        .map(TextView::getText)
        .delay(500, TimeUnit.MILLISECONDS)
        .filter(delayedText -> TextUtils.equals(delayedText, myTextView.getText())
        .subscribe(delayedText -> Log.d(TAG, "TextView paused editting at: " + delayedText);

This block is attempting to find when the user has not typed a new character in a .5 second window, but it doesn't work because the .map() also gets delayed and the call to TextView.getText() returns the most recently updated text, not the text .5 seconds ago. Using ViewObservable.input() instead of the first two lines does work.

My goal when I wrote ReactiveX/RxJava#1545 was to provide flexibility to get a CharSequence as opposed to just a String from ViewObservable.input(TextView) but I figured just emitting the TextView itself was more flexible. This is likely problematic for lots of Rx operations where you want to emit immutable values, especially when they are shared across multiple threads.

I tried looking at #5 but I'm not sure this works for all cases. I think it's probably good to have a different solution that captures the text change value immediately and also emits a CharSequence. Anyone have any suggestions on the best way to ideally avoid breaking changes?

[zsxwing]

delay(delay, unit, AndroidSchedulers.mainThread()) can solve your problem. It will run the work in the UI thread.

[nsk-mironov]

It was my mistake to make ViewObservable.input to return Observable<String> instead of Observable<CharSequence> and I agree that it should Observable<CharSequence>. But I don't like the idea that a TextView itself should be emitted. Then reason I made ViewObservable.clicks to return Observable<View> is that there is no any another value to emit when the View is clicked. Of course, it could be Observable<Void> but it seems a bit weird for me.

I think we should change the return type of ViewObservable.input to Observable<CharSequence> (and probably rename to ViewObservable.text) and remove the existing ViewObservable.text method. I know that it's a breaking change, but it shouldn't be difficult to migrate.

[ronshapiro]

I did a little bit more investigation into this and delay(delay, unit, AndroidSchedulers.mainThread()) did not work either. The Scheduler parameter only schedules the delaying, but the issue is the mutable value being emitted since .getText() can return an Editable.

If you include an extra map to .map(CharSequence::toString() or .map(SpannableString::new) before the .delay(), everything works as intended. I think the best solution is to return a cloned CharSequence via new SpannableString(CharSequence), or to return the instance directly and include a disclaimer that it may be mutable.