Hello!

hi! sorry for the delay!

how can I help you today?

I'm working with chrome custom tabs today

I have never used those, so my ability to help may be limited

ok. I'll describe the problem.

Activity A needs to kick off a chrome custom tab(CCT). When the CCT is closed, my app should return to Activity B.

Or, Activity A should know that the CCT ended and finish itself

Activity B is decided by a TaskStackBuilder that was created earlier.

I don't know exactly what "ended" or "closed" means with respect to the CCT

if you mean that the user was in the CCT, then pressed BACK, Activity A will know that it was restarted via lifecycle events

CCT opens a chrome tab. There's an x in the top left that can be pressed to return to the activity that launched the CCT

OK, same thing: Activity A can detect via lifecycle events that it was restarted

assuming that Activity A also tracks whether it started the CCT, it can then know if it was restarted as part of coming back from the CCT

ok so I can just set a boolean to check if the CCT was launched, then check that boolean in Activity A's onResume?

yes, though you will want to track that boolean in the saved instance state Bundle, in case a configuration change occurs while the CCT is in the foreground

ok

all right I'll go with this solution.

I have one more question about LiveData

I know a lot more about LiveData than CCT, so that's promising! :-)

I'm working on this SDK design, and trying to avoid exposing our custom Deferred objects.

I seem to recall us discussing that in a past chat

so, the app layer will call some method like user_get_contacts

actually

app layer will call getCallSurvey(int callId)

normally, this method would return a Deferred object

I've implemented it to return a MutableLiveData object

a ViewModel object makes the call

and an Activity registers itself as an observer through the ViewModel.

the actual data is a String directing the user to a survey in CCT

this all works right now

but what if the server can't give the url because I don't have the right auth token or the request times out or something like that?

Does the LiveData type need to be a new class like "Result" that can also have an exception in it?

yes

this API is in Java (with a planned Xamarin consumer) IIRC, right?

right

in that case, your LiveData either is of some overall Result class that can hold all the states, or it is of some interface with implementations for the possible states

in the former approach, Result would hold the String, the Throwable (for the error), and some indication of which of those this Result represents (e.g., a boolean or enum value)

got it

in the latter approach, Result is in interface with something like ContentResult and ErrorResult implementations, and the consumer uses instanceof to determine which is which

if this were Kotlin, sealed classes is the typical approach

BTW, before I forget: from an API design standpoint, have your API expose LiveData, not MutableLiveData, unless callers can post stuff

the actual object might be a MutableLiveData, but have the method signature return the LiveData supertype

implementation hiding, and all that

yeah that makes sense.

we already have this Result logic in place. I'll try to refactor that.

ok. I've got a good direction to go in now.

thank you for the help!

you're welcome!

ok I'm off to work. Have a good day.

you too!