Listview and Adapter
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The document discusses how ListViews and Adapters in Android work together to display lists of data efficiently. The Adapter reuses views to avoid inflating new views unnecessarily, returning existing views to the ListView when possible and caching views that are no longer visible but may be needed again. This approach allows ListViews to scale efficiently to display large amounts of data without performance issues.
Listview and Adapter
- 1. http://android.amberfog.com/?p=296 Join room on qicus bit.ly/androiduii Listview and Adapter
- 2. Arif Akbarul Huda Android Developer di qiscus Penulis 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”
- 3. Good reference ● javatpoint.com/java-oops- concepts ● oodesign.com ● c4learn.com ● Livecoding! 9 Aplikasi Android Buatan Sendiri
- 6. How it works? ● ListView asks adapter “give me a view” (getView) for each item of the list ● A new View is returned and displayed
- 7. Q : what if we have one billion items? Create new view for each item?
- 8. Q : what if we have one billion items? Create new view for each item? A : Android caches views for you :)
- 9. 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/
- 11. 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
- 12. 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
- 13. 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
- 14. 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
- 15. Lets try to practice it! See project on https://github.com/omayib/ListviewInspection