listview and adapter
TRANSCRIPT
http://android.amberfog.com/?p=296
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Listview and Adapter
Arif Akbarul Huda
Android Developer di qiscusPenulis buku “Livecoding! 9 Aplikasi Android Buatan Sendiri”[email protected] (email) | @omayib (Twitter)
“jika pelukis memilki kanvas untuk mencurahkan imajinasinya,Maka programmer punya RAM yang bisa di manipulasi sesuai
imajinasi”
Good reference
● javatpoint.com/java-oops-concepts
● oodesign.com● c4learn.com● Livecoding! 9 Aplikasi Android Buatan Sendiri
Behind the screen
How it works?
● ListView asks adapter “give me a view” (getView) for each item of the list
● A new View is returned and displayed
Q : what if we have one billion items? Create new view for each item?
Q : what if we have one billion items? Create new view for each item?
A : Android caches views for you :)
ListView is designed for scalability and performance. In practice, this essentially means:● It tries to do as few view inflations as possible.● It only paints and lays out children that are (or
are about to become) visible on screencode.
http://lucasr.org/2012/04/05/performance-tips-for-androids-listview/
Add Item Clear
User : add item 1 and dispay it!
ListView : “hey adapter, give me a view..!”
Adapter : “ok, but we don't have”
“i will create a view by inflating selected layout”
“then I will keep this view on my scrapview collection
for use letter”
“wait a seconds..i set your data”
“oke done, there is a view for you”
ListView : “yah! Thanks, render was succedeed”
Item 1
View tag : 001
Add Item Clear User : add item 2 and dispay it!
ListView : “hey adapter, give me a view..!”
Adapter : “ok, but the view I created before still used
for item 1 so we don't have any stock”
“i will create a view by inflating selected layout (again)”
“then I will keep this view on my scrapview collection
for use letter”
“wait a seconds..i set your data”
“oke done, there is a view for you”
ListView : “yah! Thanks, render was succedeed”
Item 1
Item 2
View tag : 001
View tag : 002
Add Item Clear
User : add item 11 and dispay it!
ListView : “hey adapter, give me a view..!”
Adapter : “i am sorry, the view will come outer space.
We no need to render it”
But I will keep current data (item 11) to set leter after
user scrolling down”
ListView : “oke noted!”
Item 1
Item 2
...
Item 9
Item 10
Item 11
View tag : 001
View tag : 002
View tag : 009
View tag : 010
Add Item Clear
Adapter : “Hei look, user move scrolling up!”
“the view with tag 001 has been released and not
used”
“i will use this view to display current data (item 11)
ListView : “oke rendered!”
Item 2
Item 3
...
Item 10
Item 11
Item 1
View tag : 001
Lets try to practice it!
See project on https://github.com/omayib/ListviewInspection