howdy, David!

how can I help you today?

Hi Mark!

Well, I'm fighting a PagerView + TabHost with Fragments, following this example: http://developer.android.com/intl/es/reference/...

David: do you have a question?

Yep, sorry, was searching for the link

actually, that sample doesn't show TabHost anymore, IIRC

the question is: Is is possible to prevent the FragmentPagerAdapter from loading all the Fragments?

FragmentPagerAdapter will load three fragments at the outset, and the rest only as the user swipes

it will ensure that it has one fragment to each side after the first swipe, so it can handle the animations crisply

you can *increase* the number of fragments it holds onto, but you cannot decrease beyond three

Yeah, I noticed. The problem is that I'm using the same fragment for each page, only changing the arguments. I download json data and present a list. What is happening is that each one is trying to update the same list, and therefore everything crashes :)

"same fragment"? do you mean the same fragment *class*, or the same fragment *object*?

This is the first time I'm working with fragments, so I know my "solution" could not be the best. Or even right...

fragment class, sorry

then they can't be updating the same ListView, because each fragment object would have its own

so the problem must be elsewhere...

either that, or you are not talking to the right fragments at the right time (e.g., you keep trying to update the first fragment)

the fragment starts requesting and processing data on "onActivityCreated", so I'm not even "talking" to the fragment

(BTW, howdy, Peri -- be with you in a moment)

thanks

David: how have you determined that "each one is trying to update the same list"?

Until now I was convinced that I was "sharing" the lists because I was retrieving the views by id, but as you said, each one has its own...

where and how are you "retrieving the views by id"?

are you calling findViewById() on the layout inflated by the fragment in onCreateView()?

on "onActivityCreated", like listView = (PullToRefreshListView) view.findViewById(R.id.live_scores_listview);

and where is "view" coming from in that code?

onActivityCreated() does not have a "view" parameter

is that from onCreateView()?

a reference from onCReateView

well, that seems OK

it would be bad if you were calling findViewById() on the activity

as the activity will have several ListViews with the same ID, all coming from the same layouts

so long as you are scoping findViewById() to be from the fragment, then you should be working with independent ListViews

why don't you grab a stack trace showing your crash, and I'll take a question from Peri in the meantime

Peri: do you have a question?

Hi, yes.

Bye the way, I figured out how to deal with the Intent nesting.

The best solution, I think, was simply to unnest it and use a state variable at the parent level. Works fine now.

well, now that you mention it, I'll make sure every findViewById is called correctly...

Sure, I'll back with more info.

Today, I'm starting on my export function. I want to output xml and have never dealt with xml before. First off, I'd like to make sure I have character encodeing straight in my minde.

Thanks

If I understand correctly, what's most commonly used is UTF-8, right? Is that a 2 byte encoding that encompasses all possible chars in the world?

UTF-8 is the most popular encoding, though Wikipedia can probably give you a better formal definition for it than I can :-)

Ok, I'll go back and read that. So, is it true that Java by default encodes all chars as UTF-8 and as well the android works that way?

Java doesn't do any encoding "by default"

certain Java *classes* might employ default encoding rules

but that would depend on the classes in question

Well, this is diverging from xml. But I need to understand this better first.

if you are generating XML, find a class/library that helps you and ensures the encoding is right, the escaping is right, etc.

What it really comes down to is text displayed to the user and user input.

neither of which are UTF-8 encoded, until they are perhaps written to a file or stream

When I define strings in the resource files, what do I need to do to make them UTF-8?

just type them, usually

I'm missing something. If I use my text editor to type them, everything is an 8-bit char.

not in any modern text editor

I've pasted 16-bit characters into things as weak as gedit on Linux for quite some time

now, something like Notepad might only use 8-bit ASCII encoding

these are questions for the people who are providing you with the tools and the classes that you are using

they aren't really Android development questions

Well, how about the eclipse editor? I use an external editor which (at least by default) displays 8 bit char, and evidentally the files are compatible between the two editors.

AFAIK, the XML editors in Eclipse will save files as UTF-8 encoded

but that's a question for an Eclipse expert

Hmm. Ok, I look at the eclipse docs.

I am not an Eclipse expert, nor an i18n expert

So, back to xml.

hold on one moment -- let's give David another shot

I tried using the XmlSerializer, but found it too lame - in particular, it doesn't escape quote characters.

David: do you have another question, or a follow-up from your first one?

Ok, no problem.

hmmm... OK, no sign of David

Peri: back to you

I haven't written an XML file from Java in several years -- I do mostly JSON

but I presume there are other libraries for XML construction than the XmlSerializer

So, I decided to write my own xml writer.

Ok, you're not the person to ask about this. That's fine.

Next question.

I'm still vascillating on whether to use internal or external storage.

On early models, apparently internal storage was limited so people had to use external for large things.

correct

Anymore (at least ver >= 4.0) is that an issue?

no

pretty much everything made in 2011 and beyond will have 1GB or more of internal storage

and Android 3.0 pretty much eliminated a lot of the internal vs. external space issues

So, I can put as large a file as total space available will allow. There's no partitioning between internal and external?

on Android 3.0+, internal and external usually share a partition, and therefore share space

Ok, that answers that part.

on Android 1.x/2.x, internal and external were separate partitions

We talked about the benefits of internal vs external before.

Bascially, if it's internal, it hides it from most users - all those who have not "rooted" their device, right?

correct

That is desirable to me. (I wish I could protect from everyoine, but oh well). Are there any other advantages?

on Android 1.x/2.x, external storage was not always available

if the storage was mounted as a drive or volume on a host PC, Android did not have access to it

that too was corrected, after a fashion, in Android 3.0

Anything else, at least regarding 4+ ?

not really

Super. May I ask another question? David?

David: do you have another question?

Hi again, no more question right now

Ok, here goes.

OK, chime in if you think of one

ok

I'd like to do a ListView incremental search, just like the one for the Contacts app.

I've tried to figure out how to do this to no avail.

Other than writing all of it from scratch.

what part of it have you had problems with?

there are a lot of pieces

There's something called a TextWatcher. During onTextChanged, I think I'm supposed to call adapter.getFilter().filter(s) where s is the text that changed. Nothing happens.

Oh, wiat, there was a preliminary part to this.

I don't understand how you get the search icon to appear.

the search icon in Contacts is an action bar item

Ok, so I need to add the search icon myself - it's not part of ListView?

or do you mean the icon to the left of "Find contacts" in the EditText?

ListView definitely does not have a search icon

The one in the action bar

on my Galaxy Nexus, the search icon is a simple action bar item, in the split action bar

@android:drawable/ic_menu_search, most likely

Ok, so then I should tie the TextWatcher to that search box, right?

what "search box"?

The EditText that appears when you tap the search icon (sorry to be vague)

first, you will need to add that EditText (custom action bar nav, most likely)

Right, I understand.

that would be what you would tie the TextWatcher to, to find out about what the user types in

And then the rest is as I said above - call adapter.getFilter().filter(s) ?

I think so, assuming you have set up the filter already

Excellent! I'll try this out.

I don't have a sample for this, and it's been probably two years since I played with filtering a ListView

I'll make a point to try to add material on this to my book, probably for the early February release

If I get it working, I can send you some code if you like :)

something I should have done a while back

oh, that's OK, there's probably plenty of samples around

and I think I have a sample here somewhere, just gotta find it

(too much code, too little time...)

You would think. Didn't find any good ones, though.

I have one very brief question, if you still have time.

sure, ~20 minutes left in the chat

(David: again, if you come up with a question, jump in)

According to some google documentation, there are four recommended sizes for icons. I am using icons as buttons and, on the nexus 7, they are appearing at a reasonable size. If I follow this standard, will they be a reasonable size on all devices?

"According to some google documentation, there are four recommended sizes for icons" -- that depends entirely on the use of the icon

As a button.

I want to be sure it is large enough to touch, but not much larger.

48dp is probably the right size for the button overall

I haven't seen this page. I guess I need to read it.

the button background will add some implicit padding

you'll have to experiment a bit

somewhere around 36dp is probably the desired size for the icon

Icons aren't declared in dp though. They're actual pixels. How do I experminet? I did try it on one other device (and it was ok).

I could make up various emulator configurations, but they might not be realistic.

the emulator should be OK, so long as you scale the emulator window to be an appropriate size

in terms of the icons, you get your pixels by converting dp to px

36dp = 36px at mdpi

Right, but I can invent any screen resolution I want and that might not be a realistic experiment.

36dp = 72px at xhdpi

the tools will guide you to common screen resolutions, densities, sizes

Ok, well let's just wait and see. It will probably be ok. I'll hear about it otherwise, I'm sure. :)

you put your icons in the appropriate density resource sets (e.g., res/drawable-hdpi/)

for whichever densities you wish to support

Yes, I did.

then if you have done your calculations correctly, they should be fine, and you can use the emulators to basically confirm your theory

Alright, I'm done for today. Thanks so much.

you are very welcome

Ok, so now I'm pretty sure the problem is not what I thought :)

David: welcome to the joys of debugging :-)

Haha, been there, but this is some "legacy" code and I think the network system was not ready for concurrent requests...

I'll have to chat with the previous developer tomorrow...

Thanks for your help, Mark

oh, OK

If I get more weird errors, I'll come back ;)

bye!

bye!

howdy, EGHDK!

how can I help you in the remaining 8 minutes of the chat? :-)

Hey Mark. I wanted to personally ask you this question, but I got stuck at work, but hope you don't get pissed if i just direct you to my SO question.

go ahead

I have to go soon (as do you), but I'd appreciate any advice. http://stackoverflow.com/questions/13839883/get...

Hopefully my question makes sense.

you really need to provide a stack trace, per the comment on the question

"causes it to crash" is not enough for anyone to really go on to give you a haned

er, hand

Hahaha, okay, uhm so you have to realize I'm new to programming. So, even though I kinda know what stack trace means... I kinda don't.

hahaha

ah, OK

I know I get a StackOverflow error. lol

when you crash, a Java stack trace is written to LogCat

First time I've seen that.

you access LogCat as a view in Eclipse

Yes, I can read logcat pretty well.

Is the entire crash report (20 or so redlines) considered the stack trace?

probably

it will cite an exception, then a bunch of references to classes/methods/lines

Okay, so I'm looking for the exception, and everything after that.

yes

frequently, the stack trace will have one or more "Caused by" lines in the middle

you want all of that too

So stack trace = logcat error report.

well, stack trace is a Java concept

been around for 15 years or so

and is also seen in other programming languages

conversely, LogCat is used for a lot more than stack traces

Gotcha. Cool. Just making sure I get it right. It's hard to ask these kind of questions on SO or something lol.

yeah, I can understand that

I have a chapter in the book, relatively early on, that gets into some of this

Gotcha. I will post a stack trace later on tomorrow. Have to go back to work. I appreciate the clarification though.

"Debugging Crashes"

Yeah, fragmentactivities are a bitch.

But thanks again. I will gather some more questions for you for tomorrow possibly.

Take care

OK, tomorrow's chat is 10am Eastern

Yep. I have an exam at 11, so I need to see if I'll be able to make it. Talk to you soon nonetheless. Night!

see ya!