如何使用Objective C以2秒的时间间隔逐个自动滚动图像？

问题描述：

我已经为少数图像集合进行了滚动视图，我希望它能够以2秒的间隔逐一自动滚动图像。通过下面的代码，我可以使所有图像一次滑动，但我希望一个图像滚动，然后相对于时间滚动。如何使用Objective C以2秒的时间间隔逐个自动滚动图像？

-(void)scrollPages{ 

UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0,0, self.view.frame.size.width, self.view.frame.size.height)]; 
scrollView.contentSize = CGSizeMake(320, 465); 

[scrollView setScrollEnabled:YES]; 
[scrollView setPagingEnabled:YES]; 
[scrollView setAlwaysBounceVertical:NO]; 
[self.uiSubView addSubview:scrollView]; 

NSMutableArray *arrImage = [NSMutableArray arrayWithObjects:@"a.jpeg", @"cat.jpg", @"s.jpeg",@"ss.jpeg", nil]; 

for (int i = 0; i < [arrImage count]; i++) 
{ 
    CGFloat xOrigin = i * scrollView.frame.size.width; 


    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(xOrigin, 0, scrollView.frame.size.width, scrollView.frame.size.height)]; 
    [imageView setImage:[UIImage imageNamed:[arrImage objectAtIndex:i]]]; 
    [imageView setContentMode: UIViewContentModeScaleAspectFit]; 

    [scrollView addSubview:imageView]; 


} 

[scrollView setContentSize:CGSizeMake(scrollView.frame.size.width * [arrImage count], scrollView.frame.size.height)]; 



CGFloat currentOffset = scrollView.contentOffset.x; 

if(currentOffset < 2500){ 

    CGFloat newOffset = currentOffset + 1250; 



    [UIScrollView beginAnimations:nil context:NULL]; 
    [UIScrollView setAnimationDuration:3]; 
    [scrollView setContentOffset:CGPointMake(newOffset,0.0) animated:YES]; 
    }

答

尝试使用dispatch_after函数进行简单递归。事情是这样的：

-(void)scrollToNextImage{ 
    //place here code for computing and setting scrollview offset 

    _weak typeof(self) weakSelf = self; //for avoiding retain cycle 
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ 
     [weakSelf scrollToNextImage]; 
    }); 
}

请注意，这种情况下的图像将滚动，即使视图 - 控制会消失。递归只会在关闭viewcontroller后结束。如果你不想要这样的行为，你可以添加额外的条件来检查在调度下一次滚动之前viewcontroller是否可见 - 你可以检查如何做他的这里：How to tell if UIViewController's view is visible

如何使用Objective C以2秒的时间间隔逐个自动滚动图像？

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