objective c - UIActivityIndicator and GCD/Threading -

i fetching list of photos server , displaying them. i'm using gcd thread server calls. got working, want add in uiactivityindicator each uiimageview show doing , appear.

i'm not sure best method be.

code:

uiscrollview *myscrollview = [[uiscrollview alloc] initwithframe:cgrectmake(0, 0, [[uiscreen mainscreen] bounds].size.width, photoview.frame.size.height)]; myscrollview.backgroundcolor = [uicolor whitecolor]; myscrollview.pagingenabled = true; myscrollview.scrollenabled = true;  myscrollview.frame = cgrectmake(myscrollview.frame.origin.x, myscrollview.frame.origin.y, (6 * thumbnail_size) + (photo_viewer_offset_colum_1 * 2), myscrollview.frame.size.height);  //get list of photos  (int = 0; < 6; i++) {     dispatch_queue_t queue = dispatch_get_global_queue(dispatch_queue_priority_default, 0);      dispatch_async(queue, ^{         nslog(@"async thread %@", [nsthread currentthread]);          //retrievethumbnailedgeotaggedphotowithphotoid make server call         myuiimageview *myimageview =  [[myuiimageview alloc] initwithimage:[self retrievethumbnailedgeotaggedphotowithphotoid:@"test"]];         dispatch_sync(dispatch_get_main_queue(), ^{             nslog(@"main thread %@", [nsthread currentthread]);              myimageview.frame = cgrectmake(myimageview.frame.origin.x, myimageview.frame.origin.y, thumbnail_size, thumbnail_size);             myimageview.backgroundcolor = [uicolor clearcolor];             myimageview.position = i;             myimageview.isenlarged = false;             myimageview.delegate = self;              int group = (i / 6);              myimageview.frame = cgrectmake((i * myimageview.frame.size.width) + (photo_viewer_offset_colum_1 * ((group * 2) + 1)),                                             photo_viewer_offset_colum_1,                                             myimageview.frame.size.width,                                             myimageview.frame.size.height);              myscrollview.contentsize = cgsizemake((myscrollview.frame.size.width * (group + 1)), myscrollview.contentsize.height);              [myscrollview addsubview:myimageview];         });     }); } 

i'm pretty sure animating , stopping activityindicator needs on main thread, not sure how include it. needs animating during "retrievethumbnailedgeotaggedphotowithphotoid" method in thread (but not main thread).

k, re-ordered it:

for (int = 0; < 8; i++) {     //create subviews first     myuiimageview *myimageview =  [[myuiimageview alloc] initwithframe:cgrectmake((i * thumbnail_size) + (photo_viewer_offset_colum_1 * (((i / 6) * 2) + 1)),                                                            photo_viewer_offset_colum_1,                                                            thumbnail_size,                                                            thumbnail_size)];      myimageview.backgroundcolor = [uicolor whitecolor];     [myscrollview addsubview:myimageview];      uiactivityindicatorview *spinner = [[uiactivityindicatorview alloc] initwithactivityindicatorstyle:uiactivityindicatorviewstylegray];      spinner.center = cgpointmake(thumbnail_size / 2, thumbnail_size / 2);      [myimageview addsubview:spinner];     [spinner startanimating];      dispatch_queue_t queue = dispatch_get_global_queue(dispatch_queue_priority_default, 0);      dispatch_async(queue, ^{          uiimage *myimage = [[uiimage alloc] init];         //only make server call in async queue         myimage = [self retrievethumbnailedgeotaggedphotowithphotoid:@"test"];          dispatch_sync(dispatch_get_main_queue(), ^{             nslog(@"main thread %@", [nsthread currentthread]);              //myuiimageview *myimageview =  [[myuiimageview alloc] initwithimage:myimage];             [myimageview setimage:myimage];             myimageview.frame = cgrectmake(myimageview.frame.origin.x, myimageview.frame.origin.y, thumbnail_size, thumbnail_size);             myimageview.backgroundcolor = [uicolor clearcolor];             myimageview.position = i;             myimageview.isenlarged = false;             myimageview.delegate = self;              int group = (i / 6);              myimageview.frame = cgrectmake((i * myimageview.frame.size.width) + (photo_viewer_offset_colum_1 * ((group * 2) + 1)),                                             photo_viewer_offset_colum_1,                                             myimageview.frame.size.width,                                             myimageview.frame.size.height);              myscrollview.contentsize = cgsizemake((myscrollview.frame.size.width * (group + 1)), myscrollview.contentsize.height);              [spinner stopanimating];         });     }); }