Office Hours — Today, December 12

← Thursday, December 10

Dec 12
3:50 PM
Mark M.
has entered the room
3:55 PM
Mark M.
turned on guest access
Kai H.
has entered the room
Mark M.
hello, Kai!
how can I help you today?
Steve
has entered the room
Kai H.
Hello, Mark.
Before Android 11 the user could choose an external storage location for the app
Mark M.
and, hello, Steve!
Steve
hi, Mark!
Kai H.
Like the SD-Card. I choosing the SD-Card as an external storage location still possible? Have there been any changes?
Mark M.
(Steve: Kai arrived a bit before you, so I'll be with you shortly!)
Steve
sure. thanks, Mark
Mark M.
Kai: if by "choose" you mean via ACTION_OPEN_DOCUMENT and similar actions, yes, that is still allowed, though the user cannot choose the root of removable storage for ACTION_OPEN_DOCUMENT_TREE
I have material on this in *Elements of Android R*
Kai H.
I was hoping this was possible without any ACTION_OPEN_* action
Mark M.
then, what specifically do you mean by "choose"?
4:00 PM
Kai H.
Display a dialog with possible storage locations (internal, external, sd-card(s)) and then choose one.
And then (some) data of the app will be written there.
Mark M.
but, um, where is the dialog coming from? do you mean a dialog that you are creating yourself?
Kai H.
Yes.
Mark M.
I think that's possible for a few more months via android:requestLegacyExternalStorage="true", but, long-term, that's impractical, other than the locations unique to your app (getExternalFilesDirs() and kin on Context)
I didn't test removable storage much with Android 11, in part because none of the Pixels have an micro SD card slot, and testing with a USB C thumb drive, frankly, is annoying
Kai H.
Would you get sd-cards and the like with getExternalFilesDirs?
I do testing with an emulator.
Dunno if that counts
Mark M.
with the plural form, yes (getExternalFilesDirs())
Kai H.
So I guess that answers my question. Should be good enough for us.
Mark M.
that will return one location per storage volume, where your app can read and write, no permissions required
Kai H.
It's not important if it's app-unique, the important part is that the user is able to choose a medium, as some want to use more storage than the phone has internally.
Mark M.
then, hopefully, getExternalFilesDirs() will suffice for your needs
Kai H.
thank you.
Mark M.
let me take a question from Steve, and I'll be back to you in a bit
4:05 PM
Mark M.
Steve: your turn! how can I help you today?
Steve
I'll paste in my question:
View paste 
We want to record users speaking into an Android phone to produce two output files: (1) one file containing both microphone and camera output, to play back to the user; and (2) a second file containing microphone output only, to transmit to an NLP service for analysis.

However, we can only either (3) record a single file with both microphone and camera output, or (4) record two files, one with microphone output and one with camera output.

Is there a way that we could either create (1) and (2) in parallel, or create (1) and then extract the microphone output from the file to create (2)?
Mark M.
I don't know of a way to create (1) and (2) in parallel, though advanced media stuff is out of my depth
Steve
ok
Mark M.
for your other option, historically I think people have wound up using stuff like ffmpeg
and that has issues (native binaries, not really designed for this sort of use)
it's possible there is some newer option for that of which I am unaware -- again, this isn't really my cup o' tea
if you have a server, you could always consider uploading the full video and ripping out the voice recording on the server
as you have a lot more horsepower and options there, albeit with a much larger upload
and, on Android 11, you might peek at MediaParser
I'm not certain if it can do what you need, but it's the closest thing that I am seeing in the SDK, given a quick scan
Steve
great, i'll take a look
4:10 PM
Mark M.
but, alas, that's all I have at my fingertips
Steve
thanks, Mark
Mark M.
happy to help!
Steve
I have a second, unrelated question
Mark M.
let me take another question from Kai, and I'll return to you for your second one shortly
Steve
of course
Mark M.
Kai: back to you! do you have another question?
Kai H.
Yes
When taking a picture, did you ever experience a phone saving the rotation data in EXIF and then having a picture rotated "the wrong way" when using some programs?
Mark M.
do you know if those programs pay attention to EXIF headers?
Kai H.
I figured not.
One of the programs is the server users upload pictures to that can be taken with our app :D
And when viewing the pictures on Windows, some honor the flag, some ask, some don't
Mark M.
push come to shove, you can rotate the image yourself, either on the phone or on that server
IOW, you check to see if the EXIF header is there and if it is, create a new image rotated based on that header, and save that rotated image
4:15 PM
Kai H.
Ok
Mark M.
I might have code in *The Busy Coder's Guide to Android Development* for that -- I know I wrote some for my early camera libraries
the biggest downside is that you might get an OutOfMemoryError, if you cannot hold two copies of the image
and, of course, if you do the work on the server, you have more power and more options
but that's really the only way to defend yourself against software that ignores those headers
Kai H.
So you encountered that sometime too. Good to know.
Mark M.
oh, yeah, it's reasonably common, particularly for Android apps where developers aren't using a decent image-loading library
in my camera libraries, I offered options for rotating the image, just to deal with that problem
let me take Steve's second question, and I'll be back to you afterwards
4:20 PM
Mark M.
Steve: back to you! hit me with your next question! :-)
Steve
I'm getting back into Android development after not doing it for a couple of years. My Android devices are old. Do you have any suggestions on an inexpensive Android device I could buy that would be good for development?
Kai H.
Is 300 $ inexpensive?
What is the price range, what does it have to have?
Mark M.
Samsung's low end devices are fairly decent (e.g., Galaxy A20/A21), but, as Kai suggested, more parameters might help
Steve
The app I'm working on now needs to be able to record AV, but that's about it in terms of anything like special features
Mark M.
just using the normal device camera and microphone?
Steve
yes. i don't need anything special
i'm willing to get something with fewer parameters to spend less money - i'd prefer well under $300
4:25 PM
Mark M.
pretty much anything that has the Play Store on it works for development
Steve
ok. the Samsung devices you mentioned would probably be fine. i'll look into those. thanks
Mark M.
Nokia also has a bunch of entry-level devices (e.g., 5.3)
Steve
great - i'll look into those as well
Mark M.
the thing to watch out with Nokia is some of those are fairly low-spec, with Android One -- that may be specifically useful if you expect your user base to be working with low-spec phones, but it can be annoying during ordinary development
Steve
k
Mark M.
and, of course, there's always buying used on eBay or similar sites
Steve
sure
Mark M.
for example, I just picked up a Pixel 3a XL, in preparation for next year's Android R release
used for $120
Steve
i see. i'll definitely keep that in mind
Mark M.
so, sub-$200 options exist, and sub-$300 shouldn't really be a big problem
Steve
great, thanks
Kai H.
The OnePlus have pretty good value and can usually be brought up to the latest Android versions with custom roms.
4:30 PM
Steve
thanks, Kai. i'll look into those as well
Mark M.
they aren't as widespread in the US, though I saw one pop up in Amazon when I was poking around while answering the question
make sure it has the Play Store on it, though, as I forget if OnePlus is purely a Google Play ecosystem firm or whether they also ship devices without Play
it might still be useful for development even without the Play Store, but there are risks of stumbling blocks
Steve
sure. i'll keep that in mind
Mark M.
let me take another question from Kai, and I'll return to you in a bit
Kai: back to you! do you have another question?
Steve
thanks
Kai H.
I read your book about Kotlin Coroutines and got the impression that LiveData is going out already, being replaced by Flows, which are already being replaced by Channels iirc.
Mark M.
you have part of that backwards
flows are replacing channels, not the other way around
Kai H.
Ok
Mark M.
I think it may even be more accurate to say "flows are wrapping around channels, and most developers will only wind up using flows"
I get a bit lost in the coroutines statements of what is and is not being deprecated
4:35 PM
Kai H.
It has just been like half a year that I looked into LiveData. It seems that things are getting replaced VERY quickly.
Is that just the normal flow of (android|developer) things or do you think there will be some kind of (temporary) stabilisation at one point?
Mark M.
LiveData debuted in 2017, so that's not super-new
and, coroutines isn't an option for Java developers
LiveData's timing wasn't stellar in terms of long-term usage
in 2017, Google had not yet endorsed Kotlin, and I forget if the first coroutines even existed
so, it's more that JetBrains is living up to the "jet" portion of their name and are moving fairly rapidly
Kai H.
They do SO much it's really staggering.
Mark M.
and, along the way, flows are stealing LiveData's thunder
yeah, JetBrains has tremendous momentum
so, LiveData itself isn't going anywhere
Kai H.
With a lot of quite good products, covering a very wide areay.
Mark M.
however, you will see more and more developers skipping it in favor of StateFlow, either to stick purely with coroutines or with an eye toward Kotlin/Multiplatform
4:40 PM
Kai H.
Let's say I have an old Java code base and I want to implement new features in a "modern" way, with like 20 % in Kotlin. What's the best way to deal with that?
Mark M.
that's kinda broad
can you narrow the scope of "deal with that"?
Kai H.
I mean considering LiveData/Channels/Flows/...
Mark M.
at 20% Kotlin? stick with LiveData
otherwise, you may find yourself needing to ratchet up that percentage faster than you want
of the three items you cited, channels are not really worth thinking too much about now for new development
Kai H.
So LiveData if I really want to stick with Java, Flows if I am open to do "as much Kotlin as needed"?
Mark M.
that's a reasonable summary
Kai H.
Thank you
Mark M.
though the first part might be more of "LiveData if I'm not in position to convert legacy Java and I don't want to run the risk of painting myself in a corner"
LiveData can work equally well with Java and Kotlin; coroutines work great with Kotlin... and aren't really something that Java can use much
Kai H.
Well. It's more that I would be very afraid of breaking the undocumented unspecified functionality currently represented by a lot of AsyncTasks than not being in the position ;-)
4:45 PM
Mark M.
the problem is that some of that code that contains those AsyncTasks might need to interoperate with some of your new stuff
it will be less risky if the new stuff is using LiveData, so you do not necessarily have to switch languages for the AsyncTask-laden code
bear in mind that, unlike framework classes, LiveData comes from libraries, and so has a long lifespan
it is possible that some framework change in Android 17 will break today's LiveData, but outside of that, LiveData will still work 6 years from now
it may not be as popular
but, popularity is only one criterion
Kai H.
Yes
Mark M.
let me take another question from Steve
Steve: do you have another question?
Steve
yes
following up on my media question:
4:50 PM
Steve
do you have any suggestions on resources that might help me figure out a solution?
Mark M.
not specifically in terms of media
Steve
ok
Mark M.
obviously, there are your standard Q-and-A options (Stack Overflow, reddit, etc.)
Steve
sure
Mark M.
and it is possible that there is some dedicated Android media programming site that I do not know of
Steve
i appreciate your help, Mark. thanks so much!
Mark M.
I have seen that there are some specific books on the subject, but traditionally-published books have a short half-life, so those media books might be out of date already
outside of that, I cannot think of anything specific to your problem spare
er, space
Steve
i haven't found most Android books helpful for that reason
thanks so much!
Mark M.
you're welcome!
we're running out of chat time, so it's open season -- if either of you have a question, go right ahead!
Kai H.
When refactoring AsyncTask, I guess testing them means wrapping their main functionality into a function and then testing that function? Which means that function can also be moved other means of background work?
Steve
has left the room
Mark M.
Kai: if that's practical, then yes, that's a nice approach
all too often, AsyncTasks are not well-isolated
and so testing their current functionality is hard
AsyncTasks often pre-date modern Android architecture considerations, so you'll have activities and fragments directly executing the AsyncTasks
4:55 PM
Mark M.
in fact, a retained fragment was kinda the go-to approach for running AsyncTasks and dealing with configuration changes
Kai H.
We use a "static task" inside an Activity/Fragment usually.
And have a class hierarchy of AsyncTasks.
Mark M.
any last questions?
5:00 PM
Kai H.
:D
X)
Mark M.
I'm going to take that as a "no"
:-)
anyway, that's a wrap for today's chat
next one is Tuesday, 8:30am US Eastern
have a pleasant evening!
Kai H.
Same
Have a good time.
Kai H.
has left the room
Mark M.
turned off guest access

← Thursday, December 10

 

Office Hours

People in this transcript

  • Kai H.
  • Mark Murphy
  • Steve