hello EGHDK

Hey Mark, I haven't been on here in a while, but I have a boatload of questions in regards to heirarchy viewer.

how can I help you today?

go right ahead

Well, to start off, only emulators can run it, correct?

Not retail devices

by default, yes

(BTW, hi, Sherman -- be with you shortly!)

Hi Mark... thanks

A rooted device can run heirarchy viewer correct?

EGHDK: however, if you add Romain Guy's ViewServer to your project, you can use Hierarchy View then

Exactly. But I want to know more about SECURE MODE

that's a firmware issue, well outside my area of expertise

Okay, you can help sherman. I will come back with another question. hah

OK

Sherman: do you have a question?

yep I do... let me know if you don't usually provide this kind of help... this is my first office hours

so, i am trying to build an app that involves mapping of information pulled from a web service that i have built

this data (XML/JSON) will be parsed and used my Google maps v2

by*

and then details will be modified

and then the data will be synced all at once back to the webserver and so on and so forth

i am wondering about a strategy to implement the syncing in android?

um

that's rather broad

hehe... okay

and 95% of it has nothing to do with Android, but rather with your Web service

well, no...

imagine the file is already generated and it is on android

or on the device already

is there some kind of pattern that i can refer to for what i am trying to do?

since I am now rather lost, I cannot point you to a pattern

if I "imagine the file is already generated and it is on android", then there is no "syncing in android" that you need a strategy for

syncing, at least when used in mobile development, usually refers to synchronizing data between a mobile client and some server

okay

so, are you trying to figure out how to update your file locally on the device?

so syncing data between a mobile client and a server

or are you trying to figure out how to synchronize data from a device to a server?

i guess i am trying to synchronize data from device to server

are you writing the Web service? or is it one somebody else wrote?

it would be a REST api that i wrote

for a server that i wrote

then what part(s) of "a strategy to implement the syncing in android" are you unsure of, so we can narrow down this discussion?

so, i am going to pull a set of data from my server

it is probably going to be a XML/JSON

do i load that data into a SQLite database of some sort to manipulate the data?

that's one possibility

then when i update the data, how should i be sending this information back?

using your REST API that you are writing

right... so is that the best idea?

if by "that" you mean SQLite, I can't answer that, as I have no idea what your criteria are for "best"

if you are doing lots of piecemeal work with the data, or doing bulk updates of some specific facet (what would amount to a column), a database is awesome

if you are mostly just reading the data in and serializing it back out, and the "out" format would be what you are sending via REST to the server, you might just keep it in the files

Okay Mark, so using a rooted device with hierarchy viewer is possible. I would also be able to see the id's of these views correct?

EGHDK: I presume a rooted device can work with Hierarchy View. I have never tried it, nor do I have any idea what limitations, if any, there may be.

but, if it works at all, presumably it gives you the same data as you would get with an emulator

Hi Mark

Sherman: in many respects, an Android device is not that different from a single-page Web application, particularly one using some sort of client-side storage

hence, if you have Web development experience, you might ponder how you would write the single-page application, then work on finding the proper Android analogues

Mark: i was doing some reading and they mentioned building a content provider to do this sort of thing... do i need to do that?

you do not "need" to do that, though there may be use cases where you find it helpful (e.g., sharing data with other apps)

EGHDK/Sherman: let me take a question from Ron, and I'll be back with you shortly

Ron: do you have a question?

Yes, My app needs a tab bar on the bottom. I've been implementing with TabHost, but not TabActivity. I have a few questions. First, I know TabActivity is deprecated. Is TabHost within an Activity?

TabHost is a ViewGroup. It can be used from a regular activity, and I demonstrate that (IIRC) in my TabHost coverage in the book

Question #2: (Not sure if I've asked you this or not) But what is the technical term for when you do (setContentView()) is that called inflating the layout? Also, when you say Button btn = (Button) findViewById(R.id.btn1) is that called "inflating the button"? I help people learn intro android, and I have to tell them to do that a lot, and I feel like there should be a term for it.

EGHDK: behind the scenes, setContentView() will use a LayoutInflater to inflate the layout. findViewById() finds views by their ID. I would not call that "inflating the button", as it has nothing necessarily to do with inflation.

Sherman: do you have another question?

I do.

Question #3: Is there currently [or was there] a difference between opening up an application that had already been launched through the "recent apps" vs the apps launcher icon

Sherman: go ahead

EGHDK: I will be with you in a bit

I am following along with your tutorials and I am trying to understand DatabaseHelper and ModelFragment (with analogues to web development)

No problem. I'm just listing them as I type! Take your time!

would DatabaseHelper be the only class that would interface with my associated SQLite db?

in the way I wrote that specific tutorial, yes

that's not the only implementation pattern that is available

you could use the aforementioned ContentProvider, and have it be the primary access point to the database

in what situation would it be looking at another implementation pattern?

you could use an ORM framework, like ORMLite, in which case the models work with the ORMLite framework to interact with the database

etc.

you would be looking at another implementation pattern as part of your normal course of design and implementation

just because *one* set of tutorials shows *one* way of doing things does not mean that it is the *only* way of doing thngs

er, things

just as the existence of GWT doesn't mean that all client-side Web development is done in Java (translated by a GWT compiler into JavaScript)

right... is there a place where i can find other ways of doing things? obviously i don't know how things are done in Android at this point.

I cover using a ContentProvider in a couple of chapters later in the book

I do not cover ORM frameworks at this time

my book is less on high-level design decisions and more laying out the tools in the toolbox that you have at your disposal

is there a reason for that? Are ORMs resource intensive?

I do not cover ORM frameworks at this time because I can only type so fast :-)

historically, ORM frameworks' overhead was a fair bit, given the weak power of the devices

nowadays, the overhead is much more manageable

okay... i am just trying to build my first app and i am having trouble linking things together so i am using your tutorial as a way of doing things that works

and there's nothing wrong with using the tutorials as an example

there is a wide gulf between "example" and "the one and only approach"

of course.

occasionally, in Android, there is only one approach to a problem, and I try to call that out

otherwise, as the Perl people like to say, "there's more than one way to do it"

so, in the case of the tutorial, I think (IIRC) that I isolated the database access in DatabaseHelper

and that's not an uncommon approach, for small apps with only a table or two

you did yes.

Sherman: let me take questions from Ron and EGHDK, and I'll be back with you in a bit

Ron: do you have another question?

yep

Following up on my question.. Yes, I was reading pages 2021-2024 of V4.7. So you're saying that this usage is supported and not deprecated? One thing I was looking for from TabActivity was the onTabSelected method or some way of knowing the user is in the current tab.

yes, TabHost and TabWidget are not deprecated

now, a bottom tab bar is an anti-pattern on Android

Anti-pattern?

http://developer.android.com/design/patterns/pu... (see "Don't use bottom tab bars)

tabs in Android go at the top

EGHDK: "finding the view by it's ID"

OK, political issue at work that I'll need to deal with. iOS apparently rejects tab buttons at the bottom and they want the apps to look similar.

I mean iOS rejects them at the top.

whoever "they" is needs to get a clue

Create and initialize the view by finding it's id? Would that also be correct?

heh

And yes Ron, don't use tabs on the bottom!

the only people who will see the iOS and Android app at the same time is the mysterious "they"

Exactly

they should be aiming for something that is natural for each platform, not trying to enforce some ill-conceived "look similar" rule

EGHDK: findViewById() does not create anything

Regardless of that how do I know the user has selected the tab for my activity?

what do you mean by "the tab for my activity"?

The same reason iOS rejects tabs on top, Android "rejects" them on bottom.

there is only one activity in this discussion AFAIK

I use setContent and an Intent to go off to another Activity, but not a TabActivity.

What would you tell a beginner android student when they have to type out: Button btn = (Button) findViewById(R.id.btn1); Sorry If I'm being picky, but I'd like to pick your brain.

Ron: *that* is deprecated

Ron: you asked, originally, if you could use TabHost and TabWidget in a regular activity, and that is possible and is still supported

activities-in-tabs is what was deprecated (ActivityGroup and its TabActivity subclass)

EGHDK: it's the same as finding a DOM node by its ID (e.g., using a CSS selector), or finding a file by a filename, or finding a building by its street address, or finding a book by its ISBN, or...

In this app, each tab would represent an entirely different interactive user interface...

Okay, I just want to make sure I'm explaining it right. I've been doing this for a while... but I'm still no expert. heh.

Ron: you would implement that using views or, more likely, fragments

e.g., use FragmentTabHost instead of TabHost

Question #3: Is there currently [or was there] a difference between opening up an application that had already been launched through the "recent apps" vs the apps launcher icon

Sherman: if you have other questions, chime in -- we're kinda in a free-for-all mode now

no problem... just taking it all in

EGHDK: by default, there should be no difference. If you tinker with launchMode in the manifest, there might be a difference, but I haven't experimented much in that area

Perfect.

i'm still trying to understand ModelFragment and it's role in EmPubLite app... how do I know if I need a class like that in my app?

Sherman: ModelFragment is designed to help retain data across configuration changes (e.g., screen rotations)

I wonder if you can answer this fairly quickly. You said "occasionally, in Android, there is only one approach to a problem, and I try to call that out" Can you think of any off the top of your head? I find that statement really interest. Maybe blog post idea?

Sherman: I cover configuration changes and various ways of dealing with them in the book -- using setRetainInstance(true) on a fragment (like a dedicated ModelFragment) is one approach

Sherman: here's a recent blog post on the topic: http://www.androiddesignpatterns.com/2013/04/re...

EGHDK: "Can you think of any off the top of your head?" -- AlarmManager for wake-up-the-device-based-on-time events

EGHDK: "Maybe blog post idea?" -- I'm not sure how

Ron: if you have additional questions, or ones I missed, chime in

Cool. Alright, last two questions. 1. Will you be attending Google I/O 2. Do you still have the links to the presentation you gave at BABBQ?

1. No

2. They should be on http://www.slideshare.net/commonsguy

http://www.slideshare.net/commonsguy/whats-new-... and http://www.slideshare.net/commonsguy/making-mon... were the two I did at the BBQ IIRC

so say i have a map

"i have a map"

and i have like 200 markers i want to put onto that map

oh, no, wait, you didn't mean that literally...

:-)

hah

would i should probably try to retain that information between screen rotations?

Awesome thanks mark. That hotdog reference you made still makes me laugh till today (and it still makes sense) I'm signing off. Thanks for your time.

EGHDK: you're very welcome

Sherman: is the data for the 200 markers *only* going to be used by this *one* activity?

yes

well...

data for all 200.. yes... but eventually i will need information from 1 single marker

in another activity

OK

you have two issues to consider: how will this one activity get to the 200 markers' worth of data, and how will other activities get to data as needed

as usual, there are several approaches

this one activity will pull this information from

DataHelper?

you could say that each activity will go to the database to get the data as needed

in that case, the activity with the map and 200 markers would probably use a retained fragment to hold onto the marker data

whether that is a dedicated ModelFragment-style approach, or just part of another fragment that needed to be retained for other reasons, is up to you

then your other activities would need to work with the same singleton DatabaseHelper

the other major approach says that you cache the 200 markers' worth of data in memory

this saves repeated database I/O, at the cost of managing the memory

you'd probably use some sort of singleton MarkerManager (or whatever) that loads the data as needed and hands it out to requesters

in that case, you don't need to retain anything in the map activity, as it can just grab the cached copy after the configuration change

is database I/O considered an "expensive" operation in Android?

well, it's disk I/O, and disk I/O can be slow

particularly for lots of data, or complex operations, or on devices with low-end on-board flash

and if i was to cache the 200 markers in memory what would I be looking at to do that?

again, you'd have some sort of singleton responsible for managing the cache, which the activities would then use as needed

okay... my advantage is that I know only Nexus 7s are going to be accessing this

What is it called when you have to change the type of something in java?

Like (Int) when using Math?

EGHDK: if you mean (float)value, that's "casting"

so something like a CacheHelper?

Sherman: you can call it whatever you want

Mark: Yes! I meant casting. Haha I couldn't remember the term. Thanks

and that's a wrap for today's chat

thanks Mark.

this transcript will be archived at http://commonsware.com/office-hours/ shortly

next chat is Thursday at 10am Eastern

have a pleasant day, all!

u too!