ScollView pageView

#import "ViewController.h"

#define ImageCount 10
#define SCREEN_WIDTH [UIScreen mainScreen].bounds.size.width
#define SCREEN_HEIGHT [UIScreen mainScreen].bounds.size.height

@interface ViewController ()<UIScrollViewDelegate>
{
    UIScrollView *_scrollView;
    UIImageView *_leftImageView;
    UIImageView *_middleImageView;
    UIImageView *_rightImageView;
    int currentImage;
    
    UIPageControl *_pageControl;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    _scrollView = [[UIScrollView alloc]initWithFrame:[UIScreen mainScreen].bounds];
    [self.view addSubview:_scrollView];
    
    _scrollView.delegate = self;
    _scrollView.contentSize = CGSizeMake(_scrollView.frame.size.width*3, _scrollView.frame.size.height);
    //設置當前scrollView顯示中間區域
    _scrollView.contentOffset = CGPointMake(_scrollView.frame.size.width, 0);
    
    _scrollView.pagingEnabled = YES;
    
    //添加imageView
    //左
    _leftImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT)];
    _leftImageView.contentMode = UIViewContentModeScaleAspectFill;
    [_scrollView addSubview:_leftImageView];
    //右
    _rightImageView = [[UIImageView alloc]initWithFrame:CGRectMake(SCREEN_WIDTH*2, 0, SCREEN_WIDTH, SCREEN_HEIGHT)];
    _rightImageView.contentMode = UIViewContentModeScaleAspectFill;
    [_scrollView addSubview:_rightImageView];
    //中
    _middleImageView = [[UIImageView alloc]initWithFrame:CGRectMake(SCREEN_WIDTH, 0, SCREEN_WIDTH, SCREEN_HEIGHT)];
    _middleImageView.contentMode = UIViewContentModeScaleAspectFill;
    [_scrollView addSubview:_middleImageView];
    
    currentImage = 0;
    
    //初始化pageControl
    _pageControl = [[UIPageControl alloc]init];
    //根據頁數返回pageControl合適的大小
    CGSize size = [_pageControl sizeForNumberOfPages:ImageCount];
    _pageControl.center = CGPointMake(SCREEN_WIDTH/2, 580);
    _pageControl.bounds = CGRectMake(0, 0, size.width, size.height);
//    _pageControl.backgroundColor = [UIColor whiteColor];
    //設置顏色
    _pageControl.pageIndicatorTintColor = [UIColor redColor];
    _pageControl.currentPageIndicatorTintColor = [UIColor grayColor];
    _pageControl.numberOfPages = ImageCount;
    _pageControl.currentPage = currentImage;
    [self.view addSubview:_pageControl];
    
    
    [self setImage];
    
    [NSTimer scheduledTimerWithTimeInterval:2.0f target:self selector:@selector(changeImage) userInfo:nil repeats:YES];
    
}

-(void)changeImage
{
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1.0f];
    _scrollView.contentOffset = CGPointMake(SCREEN_WIDTH*2, 0);
    [UIView commitAnimations];
    currentImage = (currentImage+1)%ImageCount;
    _scrollView.contentOffset = CGPointMake(SCREEN_WIDTH, 0);
    [self setImage];
}

-(void) setImage
{
     _pageControl.currentPage = currentImage;
//    加載默認圖片
    _leftImageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"%d",(ImageCount+currentImage-1)%ImageCount]];
    _rightImageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"%d",(currentImage+1)%ImageCount]];
    _middleImageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"%d",currentImage]];
}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    //若是向右滑動
    if (scrollView.contentOffset.x == SCREEN_WIDTH*2) {
        currentImage = (currentImage+1)%ImageCount;
        scrollView.contentOffset = CGPointMake(SCREEN_WIDTH, 0);
        [self setImage];
    }
    //若是向左滑動
    else if(scrollView.contentOffset.x == 0)
    {
        currentImage = (ImageCount+currentImage-1)%ImageCount;
        scrollView.contentOffset = CGPointMake(SCREEN_WIDTH, 0);
        [self setImage];
    }
}