iphone - Scrollview didn't scrolling after dismissViewControllerAnimated -

i'm calling view controller mainscreen following code:

visualizarfotoviewcontroller *visualizarfoto = [self.storyboard instantiateviewcontrollerwithidentifier:@"visualizarfoto"]; [self presentviewcontroller:visualizarfoto animated:no completion:^{     [uiimageview animatewithduration:0.5 animations:^{         visualizarfoto.visualizarfoto.contentmode = uiviewcontentmodescaleaspectfit;         visualizarfoto.visualizarfoto.image = _fotoprincipal.image;         visualizarfoto.viewprincipal.alpha = 1;         visualizarfoto.telaorigem = 2;      }]; }]; 

to come mainscreen dismiss view controller following code:

[uiimageview animatewithduration:0.2 animations:^{     _viewprincipal.alpha = 0; } completion:^(bool finished) {     [self dismissviewcontrolleranimated:no completion:nil]; }]; 

my issue when come mainscreen, scrollview doesn't answer scrolling gesture. i've tried use [_scrollview becomefirstresponder] in viewdidappear section no success. have hint solve please? thanks

if there looking answer, did solve issue:

- (void)viewdidlayoutsubviews {     // define scrollview size accordingly number of pages     [_scrollview setframe:cgrectmake(0, 43, 320, 450)];     [_scrollview setcontentsize:cgsizemake(320 * 3, 450)]; }