hi Mark

hello, MyWay!

how can I help you today?

always playing with the chat app, don't know if you remember, if the user scrolled up, I wanted to stop adding messages to the listview, to do so I've added an OnScrollListener listener, but then I thought I could simply stop sending notifyDataSetChanged, but I can't, or otherwise I get an error, because the listview isn't sync with the adapter

I would like to still add messages to the adapter, but not to show in the listview

is there any way?

buffer those messages elsewhere, and add them to the adapter when you are ready to show them

not really

I mean, you could try row layouts that are invisible or something, but I would expect UX oddities to result

just buffer them, and when you want them shown (e.g., user scrolls back down), add them en masse

ok, so I should buffer them elsewhere

do you think it's better to buffer all messages then, or only these messages?

I mean, like doing the buffer for the messages being added, too

um, I thought "these messages" were the "messages being added" while the user was scrolled up

as I understand it, you are trying to pause normal updates to the ListView while the user is not viewing the latest messages

if so, you are buffering while you are paused, and you are not buffering while you are not paused

sorry, by these messages I meant the ones waiting for the user to scroll to the bottom

because currently I'm buffering the messages when the app is not in foreground, too

ah

but I'm doing it from the Service and I don't know if it's a good practice to check if a fragment is there from the service and if it wants messages or not

and check if it wants*

I'm not sure what "it" is in "doing it from the Service"

I'm adding messages to the adapter or to the buffer from the service

because maybe the app is not in foreground

um, that's seriously bad

your service should have no access whatsoever to your adapter

at least, no direct access

or better, not directly to the adapter, but to the list the adapter is using

in normal (non-paused) operation, the service should be using an event bus or a similar mechanism to say "hey! we got a chat message in!"

the fragment can be a subscriber to that event, and add the message to the adapter upon receipt

yes, I add it to the underlying logic using eventbus

then when the activity is ready, I get these messages queued/buffered

well, perhaps you can extend the "activity is ready" to cover cases like when the user has scrolled up the transcript

and I tought I could do the same for the scroll, but I don't know if checking for a fragment inside a service is a good thing

you wouldn't be "checking for a fragment inside a service"

the fragment would tell the service "we're scrolled up, move into the paused state"

and the fragment would tell the service "OK, the user scrolled back down again, resume normal delivery"

ah, so the fragment should send a message, e.g. with eventbus to the service

and the service store it

or startService()

right

what I am calling "paused" is a state, controlling the behavior of the service

whether it sends incoming messages in real time or is buffering them

your UI layer needs to tell the service when to switch between these states

yes, as I have many dynamic fragments I could use an hash with the name of the fragment and a boolean value

there are multiple channels, routing to different fragments?

yes

multiple channels, multiple private conversations

but every fragment name is different

I don't know about the "hash" bit, but yes, presumably you need independent buffers per channel/conversation

yes, something like that

I'd use some other identification system than a hash, such as unique int, or a UUID if these things are meant to be persistent

ok, thank you

I have a strange bug, too, which I didn't investigate, maybe you have some idea: sometimes when the user lost the connection and get reconnected, messages get added to the wrong fragment, e.g. my messages to you are added to another user, but I'm using findFragmentByTag to get the right fragment

maybe something happens because fragments have two references and get reused with a different tag?

sorry, no clue

then I have Mark's fragment which now points to something else, too, have to investigate

is there any way to simulate lost of connection on the emulator?

the Android Console may have an option for that

telnet localhost 5554

where you replace 5554 with the number shown in the title bar of your emulator window

ah, nice

help will list commands

there's commands for configuring the emulated network connection

I know it handles stuff like simulated latency

I forget whether it handles off/on

thank you, I'll check it

hi

Hello

hello, Nikhil!

Nikhil: MyWay has had a chance to ask a question already, so it is your turn -- do you have a question?

I have read 200 pages of book and I have a question about format of book

you will see uses of some of those in later chapters

findViewById(), for example, might be on the next page

however, there are plenty of cases where I point out capabilities at a high level but do not go into details

So for details where should I focus on

Will it come by practice?

it will come when you find a need to use those capabilities

OK thank you. That will be all from my side

um, OK

MyWay: your turn! do you have another question?

no, thank you Mark

OK, well, if you come up with another one, chime in

thanks

that is a wrap for today's office hours chat

the transcript will be posted to https://commonsware.com/office-hours/ shortly

the next chat is Tuesday at 4pm US Eastern

have a pleasant day!