performance - In which cases should I use SQLite on Android to cache data? -

so, write client video platform.

let's see @ 1 of features of app: fetching video.
now, use rxjava + retrofit fetch video , display it.
below code without caching:
retrofit api:

@get("/api_v3/?service=media&action=list&pager%3aobjecttype=kalturafilterpager&pager%3apagesize=500&pager:pageindex=1")     observable<kalturavideoresponse> getvideolistobservable(); 

and usage in activity:

api.getvideolistobservable()                 .doonerror(t -> t.printstacktrace())  //handle error                 .map(r -> r.getobjects())  //get business objects response                 .doonnext(l -> videoactivity.this.runonuithread(() -> fragment.updatevideolist(l)))  //update ui                 .doonnext(l -> kalturavideolist.addall(l))  //save objects memory                 .subscribeon(schedulers.io())  //do in background thread                 .observeon(androidschedulers.mainthread())  //handle result in ui thread                 .subscribe(); 

advantages:

• very simple code
  
• simple handling exceptions
  
• simple data manipulations (using rxjava operators)

disadvantages:

• at every sreen rotation new httprequest
• a lot of anonymouse classes
• if frequently, oom on not top devices. example, on alcatel 1 touch 4033d

and other example. using syncadapter + contentprovider. not add code of syncadapter configuration, add code, responsible video synchroniztion

private void updatevideolist(){         kalturavideoresponse videolist = api.getvideolist();         getcontext().getcontentresolver().delete(kalturavideocolumns.content_uri, null, null);         for(kalturavideo video : videolist.getobjects()){             final kalturavideocontentvalues values = new kalturavideocontentvalues();             values                     .putcategories(video.getcategories())                     .putcategoriesids(video.getcategoriesids())                     .putdataurl(video.getdataurl())                     .putdescription(video.getdescription())                     .putname(video.getname())                     .putdownloadurl(video.getdownloadurl())                     .putduration(video.getduration())                     .putkalturaid(video.getid())                     .putthumbnailurl(video.getthumbnailurl());              getcontext().getcontentresolver().insert(kalturavideocolumns.content_uri, values.values());         }     }   getcontext().getcontentresolver().insert(kalturavideocolumns.content_uri, values.values());         }     } 

this function called every time, when syncadapter synchronizing. @ configuration every 30 min.

and getting data @ activity(using cursorloader):

@override     public loader<cursor> oncreateloader(int i, bundle bundle) {         final string sortorder = kalturavideocolumns._id + " desc";         return new cursorloader(                 getactivity().getapplicationcontext(),                 kalturavideocolumns.content_uri,                 null,                 null,                 null,                 sortorder);     }      @override     public void onloadfinished(loader<cursor> loader, cursor cursor) {         kalturavideocursor videocursor = new kalturavideocursor(cursor);         if(videocursor.movetofirst()){             videoadapter = new videoadapter(getactivity(), cursor, true);             viewholder.videolist.setadapter(videoadapter);             viewholder.videolist.setonitemclicklistener(onitemclicklistener);         }     } 

at code fetching videos, cached syncadapter , display using videoadapter.

advantages:

• i don't lot of httprequests, every 30 mins.
• simple activity lifecycle handling
• very fast loading , displaying data

disadvantages:

there 2 fatal disadvantage.

• if video edited or deleted, don't know it.

• if frequent synchronization(for example every 3 min), app works slow...

how can fix problem?

when start learning android, found beautiful android course on udacity. in course developed sunshine app. , in app used syncadapter, cached data in sqlite. in sunshine app data weather, updates not frequently.
need frequent synchronization see, if changes occured. need improve caching/synchronization code, or should request every time when need data?