ScrollView 之 实现视图的循环显示

视图的循环现实一般采用的是412341的方法，先面试例子

#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

上面就是实现的所有代码，主要就是用到了scrollview的一个代理方法，和scrollview的一个scrollRectToVisible:方法。