hello, tinoper!

how can I help you today?

hi all

hello, Gabriele!

tinoper: do you have a question?

tinoper: I will come back to you in a bit to see if you have a question

Gabriele: your turn! do you have a question?

I'm playing with ArrayPagerAdapter, but probably I don't understand something. I'm looping over getExistingFragment, to check if a Fragment exists, if not I'm doing add(new SimplePageDescriptor(...)) and then looping again (or getting the last added) trying to get this fragment, but it's null, why?

I expected my fragment to get created, after calling add()

no, add() arranges for the page to be added

it will not actually be added until the ViewPager requests it

that will trigger your createFragment() call

and so you know at that point in time that the fragment is created, because you are creating it

hm, if createFragment don't get called, where can the problem be?

I have no idea

well, rephrase that

it will only be called when the fragment is needed

suppose your ViewPager has 5 pages in it

and you are presently showing page 0

and you add() a page, which is the 6th page

the fragment won't be created then, because there's no need for the fragment just yet, just as the fragment for position 4 won't have been created yet

oh true, when I swipe and the next page is mine, it gets called

right

if you need the fragment in advance, you're welcome to create it, then return the already-created fragment in createFragment()

ArrayPagerAdapter, like FragmentPagerAdapter, is responsible for the FragmentTransaction

and so you wouldn't want to put the fragment in the UI itself, but you could create it

the real vision is that your PageDescriptor serves in this role instead, so that you create the descriptors in advance, and only create the fragments if/when needed

I see

after createFragment has been called, I'm doing: SubFragment f = ((SubFragment)mAdapter.getExistingFragment(i));, to get this fragment

(looping over i, always), but it's still null

now I don't understand why, if I made the fragment from createFragment

if you mean that you are looping inside of createFragment(), that won't work, as I won't have had any chance to use the fragment yet

no, I'm looping out from createFragment

and, there's still a FragmentTransaction that has to be processed

I thought that as I'm out of it, the fragment should be there... is there a way to check fragment that exists in my app? a sort of debug?

I can't understand if the fragment is there and the error is inside my code (probably) or whatever

not really

getExistingFragment() is a one-liner

return (T)(fm.findFragmentByTag(getFragmentTag(position)));

it will only work once the FragmentTransaction has been processed for the newly-created fragment

which will be sometime after createFragment() has been called

but exactly when depends on the state of the main application thread's work queue

to understand better, I'm receiver a privatemessage from the irc client, as I receive it, I check if there exists a fragmentwindow for it

getExistingFragment() also requires stable fragment tags (i.e., your descriptor is not synthesizing some tag on the fly that might change from call to call for the same descriptor)

if not, I'm making it and then I should add the message received to the fragment

then call findFragmentByTag() yourself

yes, tag is stable

you know the tag, as you're defining it

getExistingFragment() is solely to find one by position

part of the reason why I am having you define the tag is so that you can retrieve the fragments by tag on your own

(as opposed to FragmentPagerAdapter, which generates tags for you using a private algorithm)

but just because a message comes in does not mean that the user has opened up the tab for the fragment

and so pushing the message into the fragment will not work

I'd raise an event on an event bus to indicate that a message was received

oh, damn; fragment is the hardest part, to me TT

and have existing fragments pull such messages

plus, as fragments are created, they need to retrieve the transcript for their private channel

which is part of your data model

you mean, received the message, send this message to all window/fragments, even if this is not the right window/fragment?

I can't understand what you mean, hm

"send this message to all window/fragments, even if this is not the right window/fragment?" -- sure

the fragment can examine the event to see if the message is destined for it

the key is that the fragment may not exist, which an event bus pattern handles well

yes, but I thought it was a waste of messages :P

if you want to push the message into the fragment *if it exists*, that's fine

but do not create fragments just because you have IRC messages

fragments are your UI; they are not responsible for storing your data model

but if it does not exist, I have to create a new fragment/windows, to handle it

no, you do not

you have to create a fragment *when the user asks for it*

by swiping to that tab

this is the part I don't understand

OK, let's draw an analogy

so, I receive the message, send the event

but then, where I should store it?

you are using a Web browser to view this chat

yes

your Web browser does not have an open tab for every Web page on the Internet

if I add a page to my Web site, your Web browser will not automatically open a tab for that page, just because I updated my server

it opens a tab when you ask the browser to open a tab

yes

right, but if click on a link (supposing it has _blank)?

(similar to receveing a message from another user, how does he know he receveid it?)

at that point, you open a tab, in response to user input

no, receiving a message has nothing to do with user input

imagine I can write to you a private message, here. I send it, how do you know you've received it, if the tab don't appear to you?

that's up to you

I

I'd consider some sort of a badged indicator in the action bar

with the badge showing the count of messages that you have received that you have not viewed

generally, on irc clients, I see an automatically-made tab, which I click

the act of receiving a message from the IRC server should update your model

it *may* update the UI, if the UI for that portion of the model exists

whether or not the UI for that portion of the model exists is largely up to the user

ah

as tab I thought I could use PagerTabStrip, can this be possible?

so I show it, even if the fragment isn't still there

sure, or the one in ViewPagerIndicator, or PagerSlidingTabStrip, or other open source implementations

adding a tab is reasonagble

but then when I tap it, I have to load from my model messages received

er, reasonable

right

so I should have a sort of MessageArchive, for every user

I'd call it a ChatTranscript, but that's just me :-)

I show the tab and when *he* likes, by swiping, I create the fragment for him

right

eheh

now it's clear, thank you

and, if when a message comes in, the fragment already exists, you can tell it that the data model has changed

for real-time updates

but if the fragment doesn't exist, don't worry about it, just add the message to the model

and the user will see the message when she eventually views that tab

to do real-time updates, you mean eventbus -> send an event for each message received, to all existent fragments, as you said before

or, if you know the fragment by tag, see if the fragment exists via findFragmentByTag()

and only try updating it if the fragment exists

I'd go with an event bus, but that's not the only solution

yes, maybe this is better, as I know the tag, so I don't send a message to them all, when I don't need to

I will have to try both solutions, anyway, I'm not able to imagine a lot, I have to practice more :P

thank you for your patience, Mark, I think I've understand it, now

if you have other questions, go right ahead

and as events are to be coupled with life cycle of activity, it's better and more comfortable, to handle events and the adapter, from the activity, right?

I am not sure what events you are referring to

I mean onEvent(BusMessageEvent ...) { ... }

whether you handle those at the activity or fragment level is up to you

inside the activity, which holds the adapter

because my messages are not related to fragments, but to the activity, I think

I wouldn't consider the ArrayPagerAdapter to be a likely candidate for handling the events

I think for today I've ended with questions :P

anyway, at least to me, fragments are harder thing to understand

I always get confused

they take getting used to

eheh, yes

thank you again, Mark, see you the next time :)

OK

hello, tinoper!

hi Mark

how can I help you today?

I was building an app that only shows one layout after another.It's like mockup to show screens not functionality

OK... but what is your question?

I means,you touch any place on first screen and it shows another.My problem was that it didn't work for more than two screens.

So, How do you suggest to do that?

I have no idea

I have no idea what you wrote, and I have no idea what "it didn't work for more than two screens" means

ok,sorry

and it is time for the chat to end, and so I don't have time to try to get the details from you now

this feels like a better fit for a Stack Overflow question

No problem,have a nice day

or you can try in an upcoming chat

the next chat is Monday at 9am US Eastern Time (same time as today's)

sorry I could not help yo utoday

er, help you today

have a pleasant day!