populate UI from local db table initially, then if webserivice has new data update table and UI

Question

ok this is my first post,

i have a ListView that is populated from local db table. from there i have to check if there is new data available from web service, if so first i have to update that particular table then UI.

now i need rough idea on how to implement this?

the data from web service isn't going to change frequently. so i need to create some architecture/mechanism where data is always loaded from database first then if new data is available from web service then i parse service update table then update UI.

basically i want something like this

    MainThread
        |
        |
        |-------->>--------separate thread----->>-----|
        |                                             |
        |                    listener/              query db,
   populate UI <<----------- observer/  ------<<----get data 
        |                    something                |
        |                                             |
        |                                             |
        |                                             |
        |                               check if we have new data--->> if no-- DONE       
        |                                             |
        |                                           if yes
        |                                             |
        |                                     call web service,
        |                                         fetch data,
        |                                        update table
        |                     listener/               |
    update UI  <<-------------observer/-----<<--------|
        |                     something               
        |

Kinda like Tumblr android App..

now i think i can achieve this with wrapping AsyncTask inside a class and an Interface(as observer/listener)

but i like to use Loader(available in android),

any other suggestion ?

Answer 1

Good question !

It seems that you are trying to achieve the Famous Google I/O design pattern? Google IO Rest design pattern, Finished ContentProvider and stuck now https://www.youtube.com/watch?v=xHXn3Kg2IQE

I did it in the past (maybe as not as well as it should have been done ;-) ). And my advice is be sure of this two points :

• Your tables are not too complex
• Your updates are not always occuring.

If it's not the case, you 'll probably face performance issues due to database accesses. But it's a really good pattern.

Another advice is to use an Event bus instead of boiler-plate, frustrating interfaces for updating the UI . (I usaully use this one https://github.com/greenrobot/EventBus no performance problems, Otto is good and simple too but does not integrate well with android-annotations).

Hope it'll help.