hello, Scott!

how can I help you today>

(great -- a typo in my second entry of the chat...)

Hey! I'm in an office hour for an online software design class right now. I do want to ask you a question though. How much longer will you be available?

today's office hours run from 7:30-8:30pm US Eastern

so, I'll be here for a bit less than an hour

ok. I'll give this thing like 10 more minutes and then just cut it off if it's still going.

I'll be asking you about recyclerviews and the new paging library stuff.

it's driving me crazy

OK, though I haven't worked with the Paging library in a year, so I'll be rusty

ok. I just started my semester with Georgia Tech's online masters in computer science program, and that was our introduction office hour by the professor. Should be a cool program!

but my JOB is android development and I'm reeeally suckin at it this week.

that's OK -- the week is almost over! :-)

next week is sure to be much better!

eh. The week will merge into the weekend unless I get this stuff worked out

Next week I go into debt!

So I'm using this paging library because one of our clients wants a contact list of 15000 users

in a single scrolling list? their fingers will get blisters

yep

there are many complications with this implementation

I'm not using Room. Everybody's using Room and all examples use Room and it's a little hard to work that out. I think I've gotten past that though.

(BTW, hello Pao -- I will be with you shortly!)

Hi

Okay

conversely, I have had limited experience with the Paging library outside of Room

I'm using the PositionalDataSource

it has loadInitial and loadRange

everything is fine when I get my first initial set of data in there until the PagedListAdapter calls tries to bind the view of the last item loaded

so, I have a screen that shows 8 or 9 items. paging library requests 90 initial items because my page size is 30 and it multiplies that by 3 by default for the first batch.

I get the 90 items and give them back to the adapter. It binds the viewable items, but then asks for the last item for some reason.

asks for it in an individual loadRange() call?

public void onBindViewHolder(RecyclerView.ViewHolder vh, int position) {

in there

it'll ask for 0-9, then 90 for some reason

oh, OK, so in the RecyclerView logic

right

in that RecyclerView method, I use getItem to get the actual data model for binding

it asks for 90, and not 89? have you loaded 90 by this point?

this is like you do in your city pop example

the position it asks for is 90

I have given it 90 items at this point

yeah, but those should be indexes 0 through 89

I know :(

unless it called loadRange() on your DataSource, you don't have a 90

asking for item 90 triggers loadRange, and that's where my problem is

because it loads 90 - 120 and then my RecyclerView jumps to the 90th item

not sure what to tell you

are you using the AndroidX edition, or the older Arch Components edition

AndroidX

they haven't updated it since January (https://developer.android.com/jetpack/androidx/...)

it's possible this is a bug

but, I have had limited experience with PositionalDataSource, and I recall it driving me nuts when I was using it

I think it's more likely I've done something dumb

I have another list that doesn't have this problem

have you played with different page sizes? say, dropping it to 20 instead of 30?

yeah

OK, I'm back to "not sure what to tell you"

I just don't have enough recent experience with this particular library to be able to tell you where you might have gone wrong

especially since it's a custom DataSource

hmm. how about some general advice on troubleshooting?

let me take a question from Pao first, and I can try to provide more troubleshooting advice when I swing back to you

Pao: your turn! how can I help you today?

sure thing

Hi, I just want to ask if there's a tool or a better way to debug a gradle build.

I actually posted this question in Stackoverflow. Is it okay to share it here?

sure

Here it is https://stackoverflow.com/questions/57604294/is...

well, the problem is coming from kapt -- how many kapt dependencies do you have?

though to your broader question, there's no real debugging option, because a Gradle script does not run when you do a build -- it ran before, creating an object model describing the build

when we do a build, Gradle is working off of that object model, not off of the script that created it

Honestly, I really can't tell how many it is because there are several modules that use it in the project.

Basically, there's no better way to debug it?

none that I know of

the specific annotation processor appears to be from data binding -- I didn't know they had an annotation processor

Oh my. I think that's it for me. Thanks Mark!

regardless, the data binding version is tied to your Android Gradle Plugin version

they just released 3.5.0 of the data binding libraries, in conjunction with Android Studio 3.5.0

and 3.5.0 of the Android Gradle Plugin

so, if you're on an older version, perhaps try upgrading to 3.5.0 and see if you get past what is probably a bug

Yeah, I just encountered it because I used the latest version. I'll play around and try to isolate the problem. Thanks.

good luck!

let me swing back to Scott, and I'll return to you in a bit

Scott: back to you!

Thank you.

well

I've been trying to implement this paging library stuff for like 2 weeks now

about the only thing that popped to mind, from a troubleshooting standpoint, is to log the crap out of your PositionalDataSource and RecyclerView.Adapter

you might consider Hugo (https://github.com/JakeWharton/hugo), to basically dump the parameters and return values

and see if anything leaps out at you

I've done tons of logging already. I need to know why the RecyclerView is asking for that item.

my next step was to attach a debugger and walk it back

I'll try that later tonight.

it just gets in the weeds of all these libraries and is a bunch of code for me to read through and try to understand

agreed

is there a better way to do that?

trying to read through recyclerview and see how it works?

reading in AndroidStudio is pretty nice, but if there's a better way that would be helpful

that's probably about as good as it will get

I mean, the source is the source

all right let's just switch gears then if you have time

Web browser and the IDE are usually the two easiest ways to view it

sure, got 15 minutes!

I got pretty far into implementing Room last weekend, but gave up late Sunday night because I thought I wouldn't have time to finish.

are you using plain SQLiteDatabase now, or something else?

I need to get a release candidate out this upcoming Sunday

nothing

meaning, no persistence?

correct

OK

we reload contacts every time the user comes back to the app.

well

it's stored in memory, but that doesn't last very long

I don't have a sense of how big of a deal it is to implement Room

I kinda felt like I could do it in a weekend, then I had a realization that there was no way that was enough time.

I've never implemented a database

yeah, I'd hold off for now

I feel like I need to be learning Kotlin too

at some point, it'll become fairly necessary

yeah

that point is not this weekend :-)

I recommend trying to learn Kotlin within the next year

how can I weave that into my job?

*Elements of Kotlin* and *Elements of Kotlin Coroutines* are part of your Warescription

oh here's a good question!

I don't know enough about your job to really answer that, but in three years' time, Java will be considered "tech debt", IMHO

I'm supposed to be writing an sdk/api (?) of the core of our app for another company to use.

they will use it in a xamarin project.

so I'm planning on making the core of the app into its own module, and then having our implementation of that in the app module

I don't know how to build just the sdk part of it for distribution though

without packaging our app with it

your SDK will be the library module

your own app module will be able to use it via implementation project(:whatever-you-call-it)

but the library module can also have the Gradle bits to be able to publish versioned artifacts to a Maven repository

(where "a Maven repository" is a fancy way of saying "a filesystem with some specific requirements")

do you have a sample project that has this setup?

there's quite a bit written about publishing open source libraries that you can use as a starting point, though your Maven repository wouldn't be Maven Central or JCenter like they use

my open source libraries need an overhaul in this area, so I don't have an up-to-date recipe in my own stuff, unfortunately

ok.

it's on my to-do list for this fall sometime

cool

I've got until end of October for this, so maybe I'll come back to you with more specific questions about the process

OK

this paging library stuff though...

it's burning my little butt!

all right I'll head off now.

I am not certain how popular it is, particularly outside of the Room-supplied DataSource

I recall when I worked with it that I thought Google bit off a bit more than they could chew, in terms of a generalization

interesting. Well I would have had to do it myself without it.

in your case, it's still probably the best solution, but I am not surprised that it is a pain for you to debugt

don't know how that would have gone

that's encouraging (seriously)

Have a good night!

you too!

BTW, this transcript will be posted to https://commonsware.com/office-hours/ shortly

and the next chat is Saturday at 4pm US Eastern