Adapter and cache technique
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The document discusses adapter and cache techniques in Android. It explains that an adapter acts as a bridge between a view and underlying data. It transforms data into views. The adapter is responsible for creating a view for each item. It also discusses using view holders and lists to improve performance. It provides examples of caching views for scrolling and caching data to avoid duplicate network requests and optimize loading images.
Adapter and cache technique
- 1. Adapter and cache technique Trí Phạm – MultiUni - 2012
- 2. Adapter and cache technique • Adapter in Android • Cache technique in Android
- 4. Adapter in Android • Adapter design pattern
- 5. Adapter in Android • Adapter design pattern (con’t)
- 6. Adapter in Android • Adapter design pattern (con’t)
- 7. Adapter in Android • Adapter design pattern (con’t)
- 8. Adapter in Android • An Adapter object acts as a bridge between an View and the underlying data for that view. • One side of the adapter is a data structure like a Java object storing data. the other side of the adapter, there is view that the data structure was transformed into. • The Adapter is also responsible for making a View for each item in the data set.
- 10. Adapter in Android • Android ListView
- 11. Adapter in Android • Android ListView (con’t) – Naive and dumb way – The correct way: List13.java – The fast way: List14.java
- 12. Adapter in Android • Considering Adapter for the List View – Each List item in the List View would be calling its “getView()” method. – This method would return a view for the List. – But creating a new View for each list item would be complicated, and the UI would be slow down. – Instead of creating new View for each item, Recycler save these view and passes it to the Adapter. – Adapter uses these view sent by the recycler, when it has to produce any new views.
- 13. Adapter in Android • View Holders – View Holders hold some data that related to an item to the view. – View Holders minimizes the amount of work, while writing the same piece of code again and again. – These are used while creating the views, where we have to use more than one time. (TextView)findViewById(R.Id.text); (ImageView)findViewById(R.Id.Icon);
- 14. Adapter in Android • View Holders (con’t) – By using the View Holders, the views are saved into a class variable and can be called when needed. holder.text = (TextView)findViewById(R.id.text); holder.icon = (ImageView)findViewById(R.id.icon); convertView.setTag(holder); – A tag can hold any kind of object, that can be set on the view.
- 15. Adapter in Android • Android ListView
- 17. Cache technique in Android • Basic cache view technique (for views that have scrolling behavior) • Cache data technique
- 18. Adapter in Android • Basic cache view technique (for views that have scrolling behavior) – Demo EfficientListView
- 19. Adapter in Android • Cache data technique – Why using cache: • Some operations are high CPU load and time consuming. E.g.: load images from network… -> Never do something time consuming twice • Mobile applications, especially Android applications needs optimization for smooth UI.
- 20. Adapter in Android • Cache data technique – Demo ImageDownloader with soft (memory) cache
- 21. Q&A