UIScrollView is created quickly

#import "ViewController.h" @interface ViewController ()<UIScrollViewDelegate> @property(nonatomic,strong) UIScrollView *scrollView; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; [self.view addSubview:self.scrollView]; } - (UIScrollView *)scrollView { if (! _scrollView) { _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 160, [UIScreen mainScreen].bounds.size.width, 200)]; _scrollView.contentSize = CGSizeMake([UIScreen mainScreen].bounds.size.width * 7, 100); _scrollView.delegate = self; _scrollView.pagingEnabled = YES; _scrollView.tag = 1001; _scrollView.showsVerticalScrollIndicator = NO; _scrollView.showsHorizontalScrollIndicator = NO; _scrollView.bounces = NO; for (NSInteger i = 1; i <= 7; i++) { [_scrollView addSubview:[self createImgView:i]]; } } return _scrollView; } - (UIImageView *)createImgView:(NSInteger)index { UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage  imageNamed:[NSString stringWithFormat:@"%ld",index]]]; imageView.frame = CGRectMake([UIScreen mainScreen].bounds.size.width * (index-1), 0, [UIScreen mainScreen].bounds.size.width, 200); imageView.layer.borderWidth = 1; imageView.contentMode = UIViewContentModeScaleAspectFit; return imageView; } @endCopy the code