Office Hours — Today, March 15

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Mar 15
3:50 PM
Mark M.
has entered the room
3:55 PM
Mark M.
turned on guest access
Janice
has entered the room
Mark M.
hello, Janice!
how can I help you today?
Janice
Hi Mark. Have to start off with a message of thanks for your books
Mark M.
you're welcome!
Janice
I received a Grow with Google Udacity scholarship, and I have been talking them up all over the Slack group
I have a question more about how to think about an Android problem rather than how to actually code it.
I'm working on an app for a local non-profit. The users will have very limited data plans so I need to take that into account.
They want to display a list of contacts of staff members (list and detail view) as well as events (also list-detail view).
I'll be grabbing those resources from a Google Calendar and a Google Sheet (easiest way for someone non-technical to update information)
I'm using Room architectural component and I've gotten to the Repository.
4:00 PM
Janice
I know this is where I need to coordinate both retrieving this information from the cloud and persisting it to the db
Mark M.
so far, so good
Janice
View paste 
Here are the questions:
1.  Since I don't want to use push notifications I will need to ping calendar and sheet periodically to look for updates.  This may sound remedial, but what would be the optimal numbers of times per day to do that?
Mark M.
you would have to ask your users what a good profile would be
Janice
2. the contacts are unlikely to change very often, so I'm not terribly worried about how to merge any new information in with old information. The calendar events, though, are a different matter.
Mark M.
with regards to polling frequency: for example, if they will only be updating the data during business hours on weekdays, there's no sense in checking for updates much outside of that window
how frequently you check within that window may be up to the OS as much as you, given Doze mode on Android 6.0+
Janice
Makes perfect sense.
this is where my newbie kicks in (I've been learning Android for 2+ years, but this is the first time I'm combining cloud data with a SQLite db)
Mark M.
so, maybe check once an hour, bearing in mind that it might wind up being less frequent, and perhaps giving users control via manual refresh or a settings screen to change the polling frequency
Janice
Also makes sense.
Mark M.
in terms of the calendar events, are you directly accessing the online calendar, or is it syncing with the local device calendar and you're using CalendarContract for accessing the local copy?
4:05 PM
Janice
Sorry. I'm formulating question and It's taking longer than I would like.
Directly accessing the online calendar
The non-profit keeps a Google calendar which is available for anyone to see
Not CalendarContract. I was going to use the Calendar API.
Then store those events in the local db.
Mark M.
is the calendar data read-only on the device, or are you accepting local changes and pushing them to the calendar?
Janice
Yes, on the device it will be read only. No local changes.
Mark M.
if there aren't a ton of entries, you could take the brute-force approach of completely overwriting the local copy on every update
Janice
Keeping in mind the data saving aspects, and sorry if this is a stupid question, is it wiser to . . . .
Yes, that was the question I was about to ask. Exactly it.
Mark M.
I don't know the Google Calendar API, so I don't know if they offer some sort of per-event last-updated timestamp or something
Janice
I'm nervous about having to update changed events.
Mark M.
at the level of an individual event, I'd just delete the local copy and replace it with what you download
Janice
Again, you anticipated my question.
Mark M.
in terms of bandwidth, ideally you could ask the Calendar API "what events have changed since such-and-so time", or the equivalent
Janice
Never thought about this, but I wonder how much data per event (on average)
Mark M.
but, again, I don't know that API, so I don't know what the options are there
usually a calendar entry is small (e.g., vCalendar/iCalendar specs), though Google could have additional stuff that could be large
for example, if you can attach a photo or something to an event
Janice
No, no worries about not knowing the API. I can figure that out. Mostly the problem is that I'm coding in a vacuum (by myself) and sometimes I get stuck in a mental loop
4:10 PM
Janice
So if I limit my query to only specific fields (excluding photos) I limit the size of the event. Makes sense.
Mark M.
if they offer that, and you don't need the larger data, that's one way to help ensure low bandwidth
Janice
The calendar API does offer that.
One last question, please?
Mark M.
sure!
Janice
So with the repository we no longer have to worry about AsyncTask and lifecycle events.
But. Is an Asynctask long enough in duration to do such a task, or should a service be used?
Best practices wise?
I've seen AsyncTask used this way, but that could result in an ANR, yes?
Mark M.
a repository shouldn't need AsyncTask, as a repository shouldn't need to do work on the main application thread
the repository should use other stuff (plain threads, SchedueledExecutorService, RxJava, etc.) for background I/O
Janice
But Asynctask has a separate thread built in ..
Oh.
Mark M.
the point of AsyncTask is to do work on the main application thread after the background work is done
Janice
Huh. Didn't occur. But it should have
Mark M.
with the repository, those things are more decoupled
Janice
Yes, it is, and I feel stupid now.
Mark M.
so the repository can be pure background, and you use other stuff (e.g., LiveData) to get the data to the main application thread when needed
anyway, in terms of whether you need a service... that depends
Janice
Yes, I'm using LiveData and Observers
depends on?
Mark M.
if the work is likely to take more than a few seconds, a service is probably a good idea
if the work is likely to be much shorter than that, a service is probably unnecessary
4:15 PM
Mark M.
the risk is if you kick off the background work, the user switches to some other app, and Android decides to terminate your process to free up system RAM
Janice
So, again, taking into account the users (low income teens) will have "starter" phones, an assuming a possible connection speed, a service could be warranted?
Mark M.
the longer the user is away, the more likely it is that your process gets terminated
Lynn Z.
has entered the room
Lynn Z.
Hello!
Janice
Isn't there a way to prioritize the app while the service is out doing work? I thought there was, but my memory fails
Mark M.
hello, Lynn! I will be with you shortly!
Janice
Sorry. Prioritize the app's outstanding service
Mark M.
Janice: well, a service helps keep your process around
which is why if the work may take more than a few seconds, a service may be a good idea
Ed T.
has entered the room
Mark M.
but, it depends on the work as much as anything
Janice
Thank you.
Mark M.
(BTW, hello, Ed! I'll be with you shortly, after Lynn!)
Janice
You have helped immensely.
Mark M.
Janice: great! let me take questions from the others, and I'll return to you in a bit
Lynn Z.
here it comes:
Janice
All done. Thank you so much Mark!
Lynn Z.
View paste 
I have delivered a signed APK to a client who uses an MDM to wrap the app for enterprise deployment.
The wrapping tool has a known ‘limitation’ (ahem bug) where it blacklists certain characters from filenames in the APK
There are some files in my APK which fall into this category.  7 files begin with a ‘$’ - 1 is [generated from?] my ic_launcher_background.xml and the other 6 are coming from the design library.
Mark M.
Lynn: your turn! do you have a question!
Lynn Z.
hmm pasting it is not very friendly to others viewing
Mark M.
Lynn: if you return and have a question, chime in
Ed: do you have a question?
4:20 PM
Ed T.
I do, thanks Mark
Janice
has left the room
Lynn Z.
Hmm, i pasted my pretyped question. you don't see it? I'll type instead
Ed T.
I see it after a 'refresh'. fyi
Mark M.
OK, if *anyone* has a question, go right ahead
Lynn Z.
I have delivered a signed APK to a client who uses and MDM to wrap the app for enterprise deployment. The wrapping tool has a known 'limitation' (bug?) where it blacklists certain characters
from filenames in the APK so fails to wrap it
THere are filenames in my APK that start with a '$' and are the culprit
Mark M.
wow, sorry -- having update problems here
Lynn Z.
1 is from my adaptive icon file $ic_launcher_background__0.xml and the other 6 are from the design library $avd_show/hide_password__0/1/2.xml
how can i remove these? should I? why are they there?
(it's ok, i'm getting a typing exercise)
Ed T.
lol
Lynn Z.
thanks for patience Ed!
Mark M.
that's a strange filename
or, more accurately, a strange directoy
er, directory
Lynn Z.
Can I remove files during the build process come from a 3rd party library? do these files event belong there?
these are files
Mark M.
beats me -- they don't look familiar, but I haven't rummaged through an APK looking for something like that recently either
is $avd_show directly in the APK root, or in some subdirectory?
4:25 PM
Lynn Z.
in the res/drawable-v21 directory
Mark M.
what version of the Support Libraries are you using?
Lynn Z.
ugh, i am now having refresh problems and cant see anything I just typed...
Mark M.
yeah, Campfire isn't having a good day -- which is odd, as they are fairly reliable
Lynn Z.
they are in the res/drawable-v21 folder
Mark M.
what version of the Support Libraries are you using?
Lynn Z.
View paste 
/res/drawable-v21/$avd_show_password__2.xml
/res/drawable-v21/$avd_show_password__1.xml
/res/drawable-v21/$avd_show_password__0.xml
/res/drawable-v21/$avd_hide_password__2.xml
/res/drawable-v21/$avd_hide_password__1.xml
/res/drawable-v21/$avd_hide_password__0.xml
can you see this pasted ^
Mark M.
yes
Lynn Z.
27.0.1
and presumably my apps file: /res/drawable/$ic_launcher_background__0.xml
sorry, 27.0.2
Mark M.
they are vector drawables and animation resources, it appears
Lynn Z.
View paste 
    implementation 'com.android.support:design:27.0.2'
right, but what of the $xxx __0.xml versions?
Mark M.
again, they are vector drawables and animation resources
the design library itself does not have those resources
so the $ stuff must be added by AAPT2 or something
this probably isn't going to be unique for you
Lynn Z.
where do they come from and why would they be in the APK ?
Mark M.
most likely, they are derived from other resources
Lynn Z.
google has proved to be not helpful to me...
Mark M.
for example, the design library has res/drawable-v21/avd_hide_password.xml
4:30 PM
Ed T.
that t-shirt would sell well :-)
Lynn Z.
right, i've located it (ha! good idea Ed)
Mark M.
that appears to be converted into three resources in the APK, two of which have the $ prefix
looks like perhaps it's one file per frame of an animated vector
regardless, it's not going to be unique for you
Lynn Z.
I know the real fix is to get Citrix to fix their MDM wrapping tool, but that's not happening anytime soon probably
Mark M.
so the MDM folk eventually have to fix their stuff
Lynn Z.
hmm so, when would those 'frames' be generated?
Mark M.
at build time, presumably
you might try researching what specific class in the design library uses those
then, see if you are using that class
Lynn Z.
plus, with a name like avd_*** I would think it would be emulator resources
Mark M.
if not, try more aggressively minifying your resources to see if you can get rid of it
but, if you're using the class that needs the resources... you're probably stuck
I think that's "animated vector drawable"
Lynn Z.
no way for me to exclude resources that come from 3rd party lib right?
Mark M.
= avd
not directly, but the minification process might remove them if you do not need them
frankly, I haven't fussed with that much, so I don't know its limits
Lynn Z.
ohhhh there just aren't enough acronyms! they should have called it $avd to fix collision haha wait, they did haha
Mark M.
let me take a question from Ed, and I will return to you shortly
Lynn Z.
no problem!
Mark M.
Ed: sorry for all the delays! do you have a question?
Ed T.
no worries
question is around a RecyclerView
I get how it works and I've done a few of the 'plain' items
4:35 PM
Ed T.
my approach has been to have a 'list' layout
and an 'item' layout
Recycler is the only thing in the List layout
and then my 'row' is in the item and I 'bind' that with the Adapter / Holder
did I describe it well enough?
Mark M.
so far, so good
Ed T.
my question is next
so I need a 'floating' header
so if I had a list of animals
I need a header for 'Reptile'
'Mammal'
things like that
and that header needs a click even that describes that 'group'
am I on the right path and is this doable ?
I'm not sure how I bind something that isn't always 'there'
Mark M.
well, there are a number of libraries that offer header support within RecyclerView
https://github.com/S64/android-sticky-recycler
Ed T.
thanks Mark!
Mark M.
https://github.com/TellH/RecyclerStickyHeaderView
and probably others, pulling from https://android-arsenal.com/tag/199
I also demonstrate headers in the book
though mine might not be "floating"
Ed T.
the book is so large... it doesn't play well with my reader. :(
Mark M.
what reader?
Ed T.
it doesn't need to float, so say...
'Preview'
on OSX
Mark M.
try real Adobe Reader
4:40 PM
Ed T.
thanks Mark! I'm good. Appreciate the help
will do on the reader item
Mark M.
FWIW, my header example is: https://github.com/commonsguy/cw-omnibus/tree/v...
the headers are just additional views, nothing special
let me switch back to Lynn, and I'll return to you in a bit
Lynn: back to you! do you have another question?
Lynn Z.
well, how would I go about trying to find which class is causing that resource to get pulled in?
Mark M.
look at the source code
we know it has something to do with passwords
Lynn Z.
right, so I know I'm not ever using that eyeball that is used for show/hide password
Mark M.
are you using TextInputLayout?
Lynn Z.
checking...
4:45 PM
Lynn Z.
I am
4:45 PM
Lynn Z.
yes, sir
Mark M.
my guess is that TextInputLayout indirectly uses those resources
Ed T.
most Enterprise systems scrub files for 'clear text' passwords. You could easily do a hash via Java but you would need to bundle a key to decrypt it. Not ideal but it would keep a simple 'sniff' test from failing....
not sure if that is your issue... and Mark is the Android guru. ;-)
Mark M.
since this isn't their own resource, but one from a library, I don't think it's that easy to change
Lynn Z.
I can't very well not use it... also, lets say I could get rid of the $avd_show/hide_password files, that still leaves the $ic_launcher_background__0.xml file in my drawable directory
Mark M.
that might be tied to adaptive icons
though I'm not seeing that resource file in the projects that I'm looking at
Lynn Z.
right, i'm sure it is because I created it in order to support adaptive icons (not the $ file version, the 'normal' version)
Mark M.
again, the build tools are what are creating these files
Lynn Z.
do you see it when you analyze an apk?
it's not there until you create an apk
Mark M.
not in the couple of projects that I looked at
but my launcher icon might be set up differently
Lynn Z.
er, in apk, not in source directory. (i may have created it incorrectly too)
workaround has been to create unsigned apk, decompress, remove offending files, recompress and then sign APK ugh
4:50 PM
Mark M.
does the resulting app run?
Lynn Z.
not maintainable as a workflow and unknown consequences of removing those files. I'm still waiting to hear if they can run it. I can install it on a device, but I need to see if they can wrap and deploy
Mark M.
I mean, I doubt that those files are there for grins
Lynn Z.
exaaactly
Mark M.
something expects them to exist
so while physically removing them might be possible... I can't imagine that being a viable approach
Lynn Z.
yeah.. I know... which is why I bought my subscription yesterday :)
Mark M.
so... I really don't know what to tell you
I mean, other than unwinding the adaptive icon and trying to avoid TextInputLayout
Lynn Z.
I'll try the optimizations suggested and breathe on the client to breathe on the MDM folks
thank you
Mark M.
sorry I didn't have a magic bullet for this one
Ed: back to you! do you have another question?
Lynn Z.
no worries. You've made me feel better about how much time I've spent on it. how soon are the chat file archives available? (today's chat)
Mark M.
within a few minutes of the end of the chat -- it's a manual thing that I do when the chat ends
Lynn Z.
gotchya
4:55 PM
Lynn Z.
Thanks again for some clues (and sanity verifications). Until next time...
Mark M.
you're welcome!
Lynn Z.
has left the room
Mark M.
Ed: any other questions?
5:00 PM
Mark M.
that's a wrap for today's chat
the transcript will be posted to https://commonsware.com/office-hours/ shortly
the next chat is Saturday, 7:30pm US Eastern
have a pleasant day!
Ed T.
has left the room
Mark M.
turned off guest access

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Office Hours

People in this transcript

  • Ed Tidwell
  • Janice
  • Lynn Zeglin
  • Mark Murphy