hello, Aaron!

how can I help you today?

Hey Mark. I have 4-5 questions I've saved up, I'll go one at a time in ascending order of difficulty

1. pages 514-523 of Busy Coder's Guide says data in a bundle persists across process terminations, and that Android's default implementation of onSaveInstanceState() automatically stores obviously user mutable data like EditText into the bundle without any action on the developer's part. But when I create an empty activity project with just an EditText, text I type in does not survive terminating the app with the back button. This seems at odds with the book's information. What am I missing?

BACK destroys the activty

onSaveInstanceState() is no longer involved, as you destroyed the logical instance of the activity

onSaveInstanceState() is for configuration changes (e.g., screen rotation) and short-term process termination (e.g., user presses HOME, then returns to the app 20 minutes later)

Ok, got it

Ok it seems there is a distinction between process termination and activity destruction that I need to research further.

they are not really related

see the "Android's Process Model" chapter (starting on page 421 of Version 8.12 of the book)

Got it.

2. Why does EmPubLite use the 3rd party MaterialTabs library instead of 1st party TabLayout? Is the point just to demonstrate using an external library or is there some other reason?

TabLayout requires appcompat, as it is part of the Design Support library; EmPubLite was set up to not use appcompat

Ok, should have realized that. Got it

3. Regarding the StackOverflow with Retrofit example, in that code you have the fragment itself implement the Callback. What's the best practice when you have multiple calls in your Retrofit interface? Java doesn't allow implementing one interface with multiple generic types. I found some example code where the implementation is done by creating a new Callback object inside enqueue() but this seems sloppy... Best alternative?

actually, anonymous inner classes (or their lambda expression equivalents) are fairly common

or, you could hook up RxJava and the RxJava call factory for Retrofit, and use RxJava chains

you're certainly welcome to create dedicated Java classes for those callbacks as well, if you prefer, but I suspect that is relatively uncommon

Ok, I'm probably not ready to learn RxJava quite yet, but good to know that the inner classes are acceptable.

4. Having finished most of your tutorials, the app I'm working on now is a Reddit client performing REST calls through Retrofit. First I create a retrofit object with the necessary base URL to get my OAuth token, but thereafter the base URL changes to Reddit's base API URL. Do I create a second retrofit object with the second base URL, or attempt to change the base URL of the first one, or do I do something altogether different? Best practice?

I have not worked with Reddit's API personally. But it feels like there are effectively two APIs: the OAuth one and the "real" one. In that case, I would have two separate Retrofit interfaces and two separate Retrofit objects.

they might share a common OkHttpClient, to use a common connection pool, thread pool, etc.

Ok, I saw some sample code online, I forget the exact method used but I believe they were specifying their own Http Client for the retrofit instance, which is something that isn't demonstrated in your book. Is that what you mean, manually specifying the client, or are you referring to something that would be performed automatically behind the scenes? I just want to make sure I understand well enough to research the same thing you are describing

"Is that what you mean, manually specifying the client" -- yes, via setClient()

Might be a poorly formed question on my part, this is all new to me

Ok

Will look into it.

Great :)

That's it for my questions. The final issue, which I am not sure is within scope of your support here, is a bug I cannot figure out which is actually related to the anonymous inner classes I created for my callbacks. I have tried to debug it without much luck. It would certainly be helpful to get your input, but I understand if reviewing more in depth code is outside what you can offer for the chat, no problem if so

if you are willing to have your code be public, I can look at it

otherwise, I can't see it :)

Sure thing. Let me commit the latest code to my Github. Will post the link momentarily

is there something specific that I should be looking at?

The code in question is in AllPostsFragment, which is a fragment that is handed to RedditFragmentPagerAdapter for use in a ViewPager (which currently only has one page)

In onViewCreated(),

I build the first retrofit instance for obtaining the OAuth token

And implement an anonymous inner class for the callbacks.

yup, I see it

But it appears that none of the code executes, neither success nor failure cases

um, OK

and you are sure that you are creating the fragment and onViewCreated() is being called? for example, "marco" is getting logged?

Yes. Marco and polo are both logged

And additionally,

If I pull the code out of the inner class and have the fragment implement the callback the way you do it in your book, it works fine

But when I put it in the anonymous inner class, it doesn't seem to be executed at all.

OK, that's strange

I tried stepping through it with the debugger but just not experienced enough to figure it out

So yeah.

Not sure what is going on

If this would be a better question to post to Stackoverflow or something, I can do that

I use the anonymous inner class callback pattern with Retrofit in some of the book examples, so it definitely works

oh

you're not holding on to any of this

your Retrofit instance and your RedditInterface instance are both local variables

so as soon as onViewCreated() returns, those variables go out of scope

that's probably not helping your cause

Ohh, that makes sense!

try making auth and riAuth fields on the fragment

and see if that helps

when the fragment itself is the callback, that object hangs around, and perhaps that's enough to keep it all working

Huh. I made auth and riAuth members of the fragment instead of local variables in onViewCreated(). The result is the same. Still nothing is logged from onResponse or onFailure.

hmmmmm...

I don't know where this is going wrong then, off the cuff

Alright. Do you think posting a question on Stack Overflow is a reasonable next step?

you might first compare and contrast your code with https://github.com/commonsguy/cw-omnibus/tree/v...

this is one of a few versions of my Stack Overflow client

the ones in the DataBinding directory use the anonymous inner class callback pattern -- see https://github.com/commonsguy/cw-omnibus/blob/v...

Ok, will take a look. Thanks. I'll let you know if it turns out to be something interesting

I also have a few general points of feedback on the book now that I'm mostly through the tutorials, which I will send you via email in a bit

Thanks a lot for your help!

you're welcome!