objective c - GCD Scrollview loading issue -


i'm using gcd load images scroll view rather following frames created makes single frame in images flicker through. here's code:

//create array     -(void)awakefromnib {  images = [nsmutablearray arraywithobjects: [uiimage imagewithcontentsoffile:[[nsbundle mainbundle] pathforresource:@"imageone" oftype:@"png"]], [uiimage imagewithcontentsoffile:[[nsbundle mainbundle] pathforresource:@"imagetwo" oftype:@"png"]], [uiimage imagewithcontentsoffile:[[nsbundle mainbundle] pathforresource:@"imagethree" oftype:@"png"]],nil];  }   //populate scrollview -(void)populate {  dispatch_queue_t queue = dispatch_get_global_queue(dispatch_queue_priority_high, 0ul);   scrollview.pagingenabled = yes; scrollview.backgroundcolor = [uicolor clearcolor]; scrollview.clipstobounds = yes; scrollview.delegate = self;  [scrollview setcontentsize:cgsizemake(2 * scrollview.frame.size.width, scrollview.frame.size.height)];  int number = [images count] ; nslog(@"%i",images);  int rowtwoint = 0; int rowthreeint = 0; int rowfourint = 0;  (int = 0; < number; i++) {        if (i <= 3) {          finalframe = cgrectmake( i*(80), 12, 80, 80);     }      if (i == 4) {         finalframe = cgrectmake(0, 95, 80, 80);     }     if ((i >4) && (i <= 7)) {         rowtwoint = rowtwoint + 80;         finalframe = cgrectmake(rowtwoint, 95, 80, 80);     }      if (i == 8) {          finalframe = cgrectmake(0, 178, 80, 80);     }     if ((i > 8) && (i <= 11)) {         rowthreeint = rowthreeint + 80;         finalframe = cgrectmake(rowthreeint, 178, 80, 80);     }       if (i == 12) {         finalframe = cgrectmake(0, 261, 80, 80);     }     if ((i > 12) && (i <= 15)) {         rowfourint = rowfourint + 80;         finalframe = cgrectmake(rowfourint, 261, 80, 80);     }       iconbutton = [uibutton buttonwithtype:uibuttontypecustom];     iconbutton.frame = cgrectmake(0, 0, 57, 57);     iconbutton.center = cgpointmake(40, 29);      [iconbutton addtarget:self action:@selector(selected:) forcontrolevents:uicontroleventtouchupinside];     iconbutton.tag = i;        dispatch_async(queue, ^{         uiimage *icon = [images objectatindex:i];          dispatch_sync(dispatch_get_main_queue(), ^{             [iconbutton setimage:icon forstate:uicontrolstatenormal];          });     });        [cell addsubview:iconbutton];         cell = [[uiview alloc] initwithframe:finalframe];  [scrollview addsubview:cell];

so doing wrong? i'm new gcd it's that. if see way improve uiscrollview performance, please let me know.

i suspect have declared iconbutton instance variable, static variable, or global variable.

each time through loop, change value of iconbutton. time twelve queue blocks execute, iconbutton set final value - reference last button created. blocks use instance (or static or global) iconbutton variable, blocks update same, final button.

make local variable reference button, , use local variable in loop:

uibutton *button = [uibutton buttonwithtype:uibuttontypecustom]; iconbutton = button; iconbutton.frame = cgrectmake(0, 0, 57, 57); ...  dispatch_async(queue, ^{     uiimage *icon = [images objectatindex:i];      dispatch_sync(dispatch_get_main_queue(), ^{         [button setimage:icon forstate:uicontrolstatenormal];      }); });

each block capture value of local variable @ moment block created, each block capture reference different button.


Comments

Post a Comment

Popular posts from this blog

monitor web browser programmatically in Android? -

i've got tricky question here. need users make payment bank (namely barclaycard) in uk. so, have https url , add parameters (such amount pay, order reference, etc) url, start http connection intent.actionview, redirect user browser can enter credit card details on bank's webpage , make payment our account successfully. far ? the code use below (i changed values privacy reasons) problem is, need app when user has completed/failed/cancelled payment. barclaycardautomatically redirects particular url when payment has succeeded, 1 if failed. there no way of knowing when barclaycard payment has succeeded go android app somehow ? button cardbutton = (button) findviewbyid(r.id.card_button); cardbutton.setonclicklistener(new view.onclicklistener() { @override public void onclick(view arg0) { string prehashstring = new string(); string prohashstring = new string(); string shapassphrase = new string(); shapassphrase = "gsvth£h70zkh...
Read more

Shrink a YouTube video to responsive width -

i have youtube video embedded on our website , when shrink screen tablet or phone sizes stops shrinking @ around 560px in width. standard youtube videos or there can add code make go smaller? you can make youtube videos responsive css. wrap iframe in div class of "videowrapper" , apply following styles: .videowrapper { float: none; clear: both; width: 100%; position: relative; padding-bottom: 56.25%; padding-top: 25px; height: 0; } .videowrapper iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; } the .videowrapper div should inside responsive element. padding on .videowrapper necessary keep video collapsing. may have tweak numbers depending upon layout.
Read more

wpf - PdfWriter.GetInstance throws System.NullReferenceException -

i'm trying create pdf document using itextsharp 5.3.4 using following document document = new document(); filestream stm = new filestream(filename, filemode.create); pdfwriter writer = pdfwriter.getinstance(document, stm); i'm getting system.nullreferenceexception following stack trace: system.nullreferenceexception occurred hresult=-2147467261 message=la référence d'objet n'est pas définie à une instance d'un objet. source=itextsharp stacktrace: à itextsharp.text.version.getinstance() innerexception: i've verified neither document nor stm null, , if select "continue" in vs12 document created - exception thrown. updated itextsharp 5.4.0 , it's still occurring. can't find information on anywhere - got ideas? make sure not catching exceptions. nullreferenceexception can 1 caught , handled inside itextsharp, don't care it. fact can continue supports theory. change following setting verify: debug -> exceptions ...
Read more