Introducing Smoothie

Smoothie is an open-source library that provides a simple API to load ListView/GridView items asynchronously, off the UI thread. Besides the obvious view recycling handling, Smoothie is gesture-aware and supports powerful features such as off-screen item pre-loading and multi-part items. In this session, you will get overview of Smoothie's features and implementation; and learn how to use it in your apps through a series of practical examples.

Transcript

1. Smoothie!
   

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2. Lucas Rocha
   @lucasratmundo • +LucasRocha
   

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3. Android and me
   Firefox for Android
   http://bit.ly/firefox-for-android
   Pattrn Wallpapers
   http://bit.ly/pattrn-app
   Smoothie
   http://github.com/lucasr/smoothie
   TwoWayView
   http://github.com/lucasr/twoway-view
   

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4. AdapterView
   Children provided by an Adapter.
   View recycling support.
   ListView and GridView.
   

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5. http://bit.ly/listview-perf
   How ListView works
   

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6. Async in ListView
   Async vs View recycling.
   Trivial to implement.
   

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7. Non-trivial bits
   Gesture awareness.
   Preloading off-screen items.
   Multi-part items.
   

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8. Smoothie!
   Easy async item loading for
   ListViews with all these non-trivial
   bits built in.
   Factored out from Pattrn.
   Nice and simple API.
   Not an image-loading library.
   (But can be used to load images off UI thread)
   https://github.com/lucasr/smoothie
   

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9. How to use it
   Add an AsyncListView to your layout.
   Implement an ItemLoader with
   your app-specific logic for loading
   and displaying items.
   Instantiate an ItemManager with
   your ItemLoader and set it on the
   AsyncListView.
   1
   https://bit.ly/smoothie-intro
   2
   3
   

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10. AsyncListView
    Encapsulates async logic.
    Behaves exactly like a ListView.
    AsyncGridView is analogous.
    1
    

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11. ItemLoader
    
    1. Fetch parameters
    2. Memory load
    3. Async load
    (Off main thread)
    4. Display
    API assumes loaded items are
    cached in memory.
    2
    

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12. SimpleItemLoader
    2
    

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13. ItemManager
    Defines the async loading
    behaviour for an AsyncListView.
    ItemManager.Builder sample here
    3
    

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14. Gesture awareness
    Async loading is disabled while the
    ListView is scrolling with finger up.
    Async loading is only enabled when
    the ListView is either idle or scrolling
    with finger down.
    In-memory items are displayed
    immediately in any ListView state.
    

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15. Preloading
    Improve perceived performance
    by showing placeholders less
    often.
    Load off-screen items ahead of
    scroll position.
    

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16. Multi-part items
    Items that require multiple
    async operations to load.
    Sets relative priorities between
    item parts.
    Inherit from ItemLoader instead.
    loadItem() loadItemPart()
    →
    loadItemFromMemory() loadItemPartFromMemory()
    →
    displayItem() displayItemPart()
    →
    https://bit.ly/smoothie-multipart
    

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18. Limitations
    Hard to blend with libraries using
    custom ListViews or GridViews.
    Hard to blend with your existing
    async loading libraries e.g. Volley.
    Preloading logic assumes user is
    scrolling the list down.
    Single type for multi-part items.
    

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19. Implementation
    Custom ThreadPoolExecutor.
    Dynamic priorities as the user
    scrolls the view.
    Checkpoints to invalidate
    obsolete async operations.
    

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20. That's all!
    Questions?
    

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