hello, ming!

how can I help you today?

Hi Mark!

First question is about notification

Is there a way to change the height my notification snippet takes in notification center?

not exactly

there are the big notification styles

but you don't control when those are shown

it's based on where you are in the notification drawer and user preference

otherwise, AFAIK, the height is controlled by Android, not developers

oh

i see an app called

watchon

it shows a remote on notification center, and it takes unusually large height

if you mean Samsung's app, I don't see their notification drawer entry in the Play Store screenshots, so I haven't seen this

i saw it on my friend's samsung s4, is it because samsung made modification to the OS?

it's possible that WatchON has different capabilities on a Samsung device than on others

in fact, looking at the available installation targets, it looks like it might *only* be available for Samsung devices

oh yes that makes sense

hence, they may be doing some sneaky stuff that only works on their devices

I really wish we can customize the notification center, just like in iOS8

ok, lets talk about listviews. I still don't fully understand how it reuses the view

so in getview() method, one of the argument is convertview, that is the view populated already and will be reused right?

if there is a view to reuse, yes

so let's say i have 10 items in my list, my screen can display 5 of them and it is displaying the first 5 items

OK

I am scrolling so that my 6th item is about to appear

so for this 6th item, which view is it going to reuse?

none of them

convertView will be null, in all likelihood

as the original five views are still visible

wait, so when is a view being reused?

it won't be reused until it is no longer visible

in a ListView, it will have scrolled off the screen

we can't reuse it while it is still visible

oh i see, so lets say my 1st item is off the screen, 2 to 6 are being displayed

at this time, is the 1st item's view being reused?

probably not

the 1st item was probably visible while the 6th was coming onto the screen

if you scroll up one more, so that 3 to 7 are being displayed, the 1st might be reused at that point

but who's going to reuse 1st view?

7?

yes

when getView() is called for the 7th row, it might be handed the now off-screen 1st row for reuse

oh i see

lets say all items contains a textView, and the text displayed is their corresponding number, 1st item is 1, 2nd item is 2 etc..

when 7th item is using 1st view

if i dont set the text to be 7, is it going to display 1?

if getView() was passed the 1st row for reuse, then yes

bearing in mind that populating this TextView might be handled by something you are inheriting in your adapter

and therefore it might be updating that TextView, not you

the only place to update textview is in the getview(), i find the reference to the textview, and call getItem(position) to find the string and set the text

that depends a bit on what adapter class you are extending and whether you are chaining to the superclass in getView()

i dont understand by how it being handled by something else

this is covered in the book

take a look at the activity

and show me where I am setting the TextView myself in a getView() method

as you'll see, I don't have my own adapter class

I am using ArrayAdapter

and ArrayAdapter is populating my TextView

yes

then, we have this sample: https://github.com/commonsguy/cw-omnibus/tree/m...

here, I am updating one TextView and one ImageView, but I am inheriting from ArrayAdapter, and it is handling the other TextView

the same thing holds true with most concrete adapter implementations in Android

oh yes

cos getview() in super class may update the view

right

lets talk more about listview

there is a method called getViewCount() and getViewType()

wait

that's getViewTypeCount() and getItemViewType()

i may got it wrong, let me googleit

oh i see. what are the purposes of those two methods

that's covered in the Advanced ListViews chapter

the chapter begins on page 823 of Version 5.9 of the book

you use those if you will have different sorts of rows, with different layouts

such as header rows and regular rows

getViewTypeCount() says how many different types of rows you have

getItemViewType() returns a value, from 0 to getViewTypeCount()-1, indicating which type of row is used for a particular position

AdapterView maintains separate object pools for view recycling

one pool per row type

so if you implement getViewTypeCount() and getItemViewType(), you are assured that the row handed to you for recycling in getView() will be of the appropriate layout

so you do not get handed a header row to reuse when you need a regular row, or vice versa

oh i see, (getItem(position) instanceof Integer) this is a really smart check

let's talk about multi threading

To me it seems that asynctask and handler they are two best options

I read the book the big nerd ranch guide, the book says use handler for long running tasks

so how do I decide which on to use

that is impossible to answer in the abstract

you choose your approach based on a specific circumstance

I am sorry :( i know that is toooo abstract

is there a way I can get access to apps produced by google?

what do you mean?

specifically, what does "access" mean?

for example

email

source code

the Email app is part of the Android Open Source Project

the Gmail app is not

source code for gmail app

to get the source code for Gmail, get a job at Google

oh im not good enough :(

the Email app's source code is at https://android.googlesource.com/platform/packa...

I think I asked all questions I have for now

OK

note that the transcript for the chat will show up at http://commonsware.com/office-hours/ once the chat is over

yes I see. Thank you so much for your time!

you are very welcome