ScrollView 之 實現檢視的迴圈顯示

檢視的迴圈現實一般採用的是412341的方法，先面試例子

#import "ViewController.h"
#define imageWidth     300
#define imageHeight    450
@interface ViewController ()<UIScrollViewDelegate>
{
    NSArray * _sourceArray;
    UIScrollView * _scrollView;
    UIPageControl * _pageControl;
}
@end

@implementation ViewController

-(void)loadView{
    [super loadView];
    
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    _sourceArray = [NSArray arrayWithObjects:@"A.png",@"B.png",@"C.png",@"E.png", @"F.png",@"G.png",@"H.png",@"I.png",@"J.png",@"K.png",@"L.png",@"M.png",nil];

    _scrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(10, 20, imageWidth, imageHeight)];
    _scrollView.delegate = self;
    _scrollView.pagingEnabled = YES;
    _scrollView.showsHorizontalScrollIndicator = NO;
    _scrollView.showsVerticalScrollIndicator = NO;
    _scrollView.contentSize = CGSizeMake(imageWidth*([_sourceArray count]+2), imageHeight);
    [self.view addSubview:_scrollView];
    
    UIImageView * firstImage = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, imageWidth, imageHeight)];
    firstImage.image = [UIImage imageNamed:[_sourceArray lastObject]];
    [_scrollView addSubview:firstImage];
    
    for (int i = 1; i <= [_sourceArray count]; i++) {
        
        UIImageView * imageView = [[UIImageView alloc]initWithFrame:CGRectMake(i*imageWidth, 0, imageWidth, imageHeight)];
        imageView.image = [UIImage imageNamed:[_sourceArray objectAtIndex:i - 1]];
        [_scrollView addSubview:imageView];
    }
    
    UIImageView * lastImage = [[UIImageView alloc]initWithFrame:CGRectMake(([_sourceArray count]+1)*imageWidth, 0, imageWidth, imageHeight)];
    lastImage.image = [UIImage imageNamed:[_sourceArray objectAtIndex:0]];
    [_scrollView addSubview:lastImage];
    [_scrollView scrollRectToVisible:CGRectMake(imageWidth, 0, imageWidth, imageHeight) animated:NO];
    
    _pageControl = [[UIPageControl alloc]initWithFrame:CGRectMake(0, _scrollView.frame.origin.y + _scrollView.frame.size.height - 20, imageWidth, 20)];
    _pageControl.numberOfPages = _sourceArray.count;
    _pageControl.currentPage = 0;
    _pageControl.enabled = YES;
    [self.view addSubview:_pageControl];

	
}



-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    int currentPage = scrollView.contentOffset.x/imageWidth;
    if (currentPage == [_sourceArray count]+1) {
        [_scrollView scrollRectToVisible:CGRectMake(imageWidth, 0, imageWidth, imageHeight) animated:NO];
        _pageControl.currentPage = 0;
        
       
    }else if (currentPage == 0){
        [_scrollView scrollRectToVisible:CGRectMake(imageWidth*([_sourceArray count]), 0, imageWidth, imageHeight) animated:NO];
        _pageControl.currentPage = _sourceArray.count - 1;
        
    }else{
        _pageControl.currentPage = currentPage - 1;
    }

}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

上面就是實現的所有程式碼，主要就是用到了scrollview的一個代理方法，和scrollview的一個scrollRectToVisible:方法。