hello, Ray

Hello

how can I help you today?

I was wondering if you had an opinion on the best way to show/hide a notification when an app is swapped between foregound and background. Like with Google Music, if you've used it

Hello

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

Ray: I guess I don't really understand the question

We'd like to show a notification when the app is closed and hide it if the app is opened

no, I got that part

We've considered using the package manager to check if the app is in front, using a counter/flag in onstart and onstop and the trim memory but these seem like hacky approaches

yeah, well, you'll wind up with one of them

there really is no "the app is moved to the background" event

there is onUserLeaveHint(), but it will not cover all cases

onTrimMemory() is the closest literal match, when you get the TRIM_MEMORY_BACKGROUND flag (or whatever that value is)

Yes, I saw your answer on SO but unfortunately onUserLeaveHint() wouldn't be suitable

Ok, just making sure we hadn't missed anything, thanks

Android's "basket of loosely-coupled components" architecture has its pros and cons, and you're tripping over a con

if the service will be running in either case (e.g., Google Music playing music), I'd go with onTrimMemory() in the service itself

Ah ok, thanks, I'll recommend it

otherwise, onTrimMemory() in a custom Application class would be a central spot

the only thing I have not experimented with is timing on when onTrimMemory() is called, as to how quickly it is invoked once you move to the background

let me take a question from Ales, and I'll be aback with you in a bit

Ales: your turn! do you have a question?

In our tests it seems to be near instant, however it was occasionally called while the app was open but this wasn't a problem for us

(Ray: onTrimMemory() will be called, but I would not expect the _BACKGROUND flag to be passed in while you are in the foreground)

Ales: do you have a question?

Hi again :) so my question is somewhat more general. I use Parse.com for notification and data storage. I'm quite ok with the library. However recently I got stuck with some issue on the service implementation.

I can try to help with general stuff, but I have never used Parse personally

so I won't know much about any particular APIs, etc. of theirs

doesn't matter

as I need custom notification, I use Broadcast receiver and want to start wakeful service

this is on some sort of push message?

but I somehow come into a problem, that bindService call won't call any of the method of the callback

well, WakefulIntentService is not designed to be use with bindService()

IntentService in general is not designed to be used with bindService()

yeah, I was afraid of that :)

the thing is I really would like to have Service with certain data access methods filled by Parse queries and so on

have it on single longer living object, I would guess that service is ok

well, IntentService is designed for transactional work: do something, then shut down

but there are two user cases... one is on notification I would like to delegate from the broadcast receiver to wakeful service

that is as you pointed out probably correct approach

yes, that's a typical model for push-style notifications

but for data access I would rather have bound service

then perhaps you have two services

but I don't understand how to avoid duplication of code in such case

well, inheritance would be out, so composition would be a better design pattern

I need to access data even from the wakeful service :(

yeah

have the common stuff implemented in a general class

have each service use an instance of the common-stuff class

sure. Sounds great. I like that you clear up that Wakeful service is not intened for such use

so that I don't need to burn time on this dead end

yes, that end is pretty dead :-)

:)

let me take a question from Ray, and I'll be back with you in a bit

sure

Ray: your turn! do you have another question?

Yes, just one, do you have a copy of the slides from yesterdays security presentation please. My computer rebooted when I tried to open them

it's just a PDF, so I would hope that the slides themselves did not cause the reboot

No, it's the computer, it's old

Thank you, regarding the _BACKGROUND flag comment, yes you're probably right. We were using the UI_TRIMMED flag which is caused on every onStop.

yeah if you got BACKGROUND when not in the background, I'd consider that a bug

which isn't out of the question, of course

True

Ales: back to you, then -- do you have another question?

Can you please recommend me from your experience some ORM that is suitable for Android and also can be used to build ContentProvider?

I have not used any ORM personally

the ContentProvider generators that I have seen have been focused on the ContentProvider itself, not using an ORM with one

having a ContentProvider implemented using an ORM is probably inefficient, as you need to be handing back Cursor objects anyway

having a ContentProvider be consumed ORM-style might be interesting, but I don't know of any ORMs that do that

but, then again, I have not looked

yes, I think that's the root for my question

I think ORMs are good for querying, but they generally don't play well with CP

it's more that CP is probably out of scope in the eyes of the ORM authors

What other options are interesting for storing unstructured data?

I have been intrigued by Couchbase Mobile

which is a JSON document store

there are a few other NoSQL options out there for Android

and for smaller data sets, it may be just as easy to use them fully in RAM, serializing them as needed to something (JSON, XML, whatever)

I've seen MapDB, which is basically persistent variant of NavigableMap

but it's quite low-level

yes, there are a few of those key-value stores floating around as well

one more thing related to storage, is there any option to use encrypted data?

and does it worth it?

if you're using SQLite today, SQLCipher for Android is an easy migration

as to whether or not it is "worth it", it depends on who you are trying to defend against

encryption solutions like SQLCipher are designed to defend the user's data against those who might try to steal that data

I would need to protect some sort of private keys

so something itself is participating in secure operations :)

who owns the keys? are they the user's keys? are they your keys to some back-end service?

in this particular case it's bitcoin `wallet` private key

so, it's the user's key

yeah

because presumably it is their wallet

yes

SQLCipher could work, though it's a bit of overkill

I think there are encrypted versions of SharedPreferences available

I have one, which is backed by SQLCipher, but that doesn't solve the size issue (SQLCipher is kinda big)

I think that there are others that just use javax.crypto

yeah

mapdb supports xtea encryption

the challenge with javax.crypto is getting everything right (e.g., key stretching), as it's rather low-level

so I can give it a try

I'm not familiar with xtea

(BTW, Ray, if you have another question, just chime in)

sure, Ray go ahead

Don't worry, I don't have any more questions. Thanks for your time

I would like to thank you a lot for your book

and also the examples

you are very welcome

great job

thanks!

BTW, if you did not catch yesterday's announcement, Version 6.0 is ready for download

I've seen right before I joined chatroom :)

I'm from Europe so there is time shift few hours I guess. You've morning right?

yes

Can you share please some general opinions about Android and robustness of the platform?

I mean, I quite fight it :)

fighting the platform isn't unique to Android

I have been fighting platforms for ~3 decades

beyond that, this chat is really more for problem-solving

if you have any other concrete questions, go right ahead

Maybe one, on one of my prototype I tried to use Navigation drawer, however I found it quite clumsy and state was spreading throughout the application quite a lot. Is there some general pattern which allows me to manage complexity of state in action bar, navigation drawer and fragments?

that is difficult to answer in the abstract

you may wind up having some dedicated Parcelable state object that everyone participates with, and that is used with onSaveInstanceState()

things that cannot really be put in a Parcel (e.g., large bitmaps) wind up being managed by a retained fragment to handle configuration changes, but then will need to get reloaded if the process is terminated (e.g., user returns to you through recent-tasks list)

interesting, I'll take a look at this approach.

I think it's all from me, thank you very much for your time. See you next time Mark.

note that the chat transcript will be posted to http://commonsware.com/office-hours/ shortly after the chat ends