hello, Guarav!

how can I help you today?

Hi all

hello, Luca!

Luca: I think Guarav is just lurking -- do you have a question?

Yes

I'm using some global singleton classes that are eager initialized with the app context inside onCreate of the Application class, i have read on some stackoverflow questions that sometimes static variables can become null on low memory and when you resume the app onCreate is not recalled. Can that happen to my singleton classes too?

"sometimes static variables can become null on low memory" -- your process can be terminated at any point when you are not in the foreground

"when you resume the app onCreate is not recalled" -- if your process was terminated, onCreate() will be called on relevant components (e.g., the activity that the user is launching)

i need the onCreate of the Application class

that too will be called when your process is starting up

ok i have other questions

On some Android code i have noticed singleton classes that uses a retained fragment to preserve the instance instead of a static variable. What is the difference?

(Guarav: if you have a question, let me know)

hi mark

singletons should have nothing to do with fragments

by which, I mean that a fragment should not be a singleton, nor should a singleton reference a fragment

a fragment can reference a singleton

the objective is to avoid singletons where possible -- that's standard Java advice, to reduce the odds of memory leaks

i wanted to ask you that.. through fragments .. is it easier.. for me to make a dasbhoard.. kind of view..

like that of linked in

or Google plus

Guarav: I have no idea, as I do not use LinkedIn nor Google+

I am just asking that for a dashboard kind of page

Guarav: I would not expect fragments to necessarily be involved in "a dashboard kind of page"

I certainly would not expect fragments to somehow make it easier

the main thing is that i have seven fragments..

but, again, there are many definitions off "a dashboard kind of page", and therefore I may be thinking of something other than what you are thinking of

which i need to go to .. as per the requirement

but i needed a central navigator..

For example there is a chat fragment.. Details fragment etc

and.. i needed to have a page.. or activity from where i can go to each fragment and come back

i hope it makes sense

and I apologize for not able to answer you before mark..

hello

Guarav: I have no means of answering your question, sorry

no problem thanks

(Jeff: Hi! be with you shortly!)

i think i am not able to communicate properly

no rush - take your time

Luca: to wrap up from your previous question, to retain data through a configuration change, use onSaveInstanceState() or a retained fragment, not a singleton

Jeff: OK, your turn -- do you have a question?

hi Mark

I was about to put my app in the store and tested on the new Droid Mini running 4.2.2. Of course, a problem occurred which I'm struggling with.

setting the camera parameter rotation to 90 degrees results in a Camera error 100 in takePicture()

setting the rotation parameter to 0 eliminates the error but the captured image is rotated 90 counter-clockwise

are you using the Camera class directly yourself, or are you seeing this using my CWAC-Camera library?

camera class directly

in general, working with the camera is full of device-specific quirks

which is why I am working on CWAC-Camera, to try to hide those problems

you might try to run my demo app on the Droid Mini and see if it works or similarly crashes

what I really worry about is solving this device's problem but the next one hits

that's a good idea - I'll try your demo app

I feel your pain :-)

I could give up setting parameters but I think most users will use portrait mode

if the demo app works in all orientations, then I must be doing something right to address this issue, and perhaps you can switch to use my library, or figure out what I'm doing differently than you

and so I'll be capturing images that are wrong

if the demo app crashes, then it's on me to get my hands on the Mini and fix it

note that not every device will actually honor the orientation properly -- I have to manually rotate the image for some devices in my library code

I'll try your demo app

(tell me when i can speak)

Luca: your turn now -- go ahead

yes - I change the orientation. this is the first time that parameters caused error 100

go ahead Luca

thanks Mark

I know that i have to use retained fragment to preserve data or asynctask for callbacks. But for something like a SQLiteOpenHelper i think that a singleton linked to an application is better, i'm right?

correct

ok

In my application i'm using both sqlcipher and openssl (the latter to encrypt big files). I have some small files (10-20k) that i need to encrypt too, is better to use a blob column in sqlcipher or encrypted files?

for security reasons, you really don't want to hold onto the user's passphrase in memory any longer than necessary

using encrypted files would require you to hold onto their passphrase, for encrypt/decrypt operations

hence, from a security standpoint, it will be better to store those in SQLCipher

that's not necessarily the most convenient solution

IOCipher would be a "middle ground" alternative

it gives you an API that looks like standard Java file I/O, but the contents are stored in SQLCipher

I hope to be covering IOCipher in the next book update, or else the one after that

i have already looket at iocipher but there are some issues like that the file must be less of the amount of ram

*looked

you will have the same problem with BLOB columns

if you need to have files bigger than that, storing them separately, encrypted, will be your only option that I can think of

Jeff: do you have another question?

Luca: do you have another question?

i'm already using openssl to encrypt big files with success and i'm using sqlcipher to store references and some other data, i wanted to understand if for small files related to a table row is better to use a blob

given your need to keep the passphrase around, I cannot say whether one approach is better than the other for small files

if either of you have additional questions, chime in

ok, regarding the passphrase thing i didn't understand.. to query the sqlcipher database i need the password anyway to call "getReadableDatabase" and "getWritableDatabase"

correct, but ideally you do that quickly after obtaining the passphrase from the user

whereas normally with SQLite, you might just hold onto the SQLiteOpenHelper instance and get the database from it when needed, with SQLCipher, you want to hold onto the SQLiteDatabase object, so you only need to use the passphrase once

sqlcipher will not hold the password in memory to encrypt/decrypt pages?

it will not hold the original passphrase entered by the user

it will have the hashed passphrase

at least, that is my understanding based on some discussions with the SQLCipher authors

ok now i have understand what you mean, but i think that is not my case because my "password" is the key that i use to encrypt normal files with openssl. This key is initially decrypted through the passphrase entered by the user

if you have another question, go right ahead

I'm using the MediaStore to get thumbnails of images stored on the device and i know that thumbnails are cached on external storage, i took a look at the Gallery app code and i have noticed that it generates thumbnail in memory from the original image without using MediaStore. Why that? Maybe because thumbnail sizes of MediaStore are not good for views dimension in Gallery?

"Why that?" -- you would have to ask Google

I have never examined the Gallery source in any detail

and hence I have no idea why they would have made any particular implementation decision

ok the last question, what is the difference between external and internal uri of MediaStore?

do you mean INTERNAL_CONTENT_URI and EXTERNAL_CONTENT_URI?

yes

I am not certain

the description of INTERNAL_CONTENT_URI does not make much sense to me

I have only ever used EXTERNAL_CONTENT_URI

I have not run experiments to see what I would get back if I used INTERNAL_CONTENT_URI, sorry

for example if i start a gallery intent to pick a media item, the returned content uri will be always something on EXTERNAL_CONTENT_URI?

I would assume so, but I have not done that specific bit of analysis, sorry

ok

thank you for all your answers

bye!

hello, Jose!

Jose, the chat is close to ending: do you have a quick question?

I am afraid I completely forgot about this session

well, that may have been my fault

it was originally scheduled for yesterday

I had to move it due to a conflict

I wanted to ask you about some architecture-design topics

but I am afraid it's too little time

probably

hopefully next week

and already looking forward to attend to your talk at the apps world europe

in london

I apologize for having had to move the session

cool!

im also a "speaker" there ^^

well... taking part in an open table discussion, not a speaker per se but

ah, the design one, right?

yeah

alas, I will not be able to attend that one, as I have an evening "In the Brain" session with Skills Matter that evening

well I would be surprised if we could tell anything you don't know already

well, I am certainly not a design expert

me neither, I'm trying to get better at it

:-)

well, with luck, you'll get a chance to hop in an upcoming chat, and we can cover your architecture questions

the next ones are Tuesday at 7:30pm and Thursday at 10am (both times Eastern)

but that's a wrap for today's chat

have a pleasant day!