輪播圖demo

一.
<p style="margin-left: 30px;">storyboard中佈局</p><p style="margin-left: 60px;"><img src="http://images.cnitblog.com/i/450136/201406/011652393221372.png" alt="" height="358" width="432" /></p>

二. 代碼

#import "YYViewController.h"

@interface YYViewController () <UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIScrollView *scrollview;
/**
 *  頁碼
 */
@property (weak, nonatomic) IBOutlet UIPageControl *pageControl;

@property (nonatomic, strong) NSTimer *timer;
@end

@implementation YYViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
//    圖片的寬
    CGFloat imageW = self.scrollview.frame.size.width;
//    CGFloat imageW = 300;
//    圖片高
    CGFloat imageH = self.scrollview.frame.size.height;
//    圖片的Y
    CGFloat imageY = 0;
//    圖片中數
    NSInteger totalCount = 5;
//   1.添加5張圖片
    for (int i = 0; i < totalCount; i++) {
        UIImageView *imageView = [[UIImageView alloc] init];
//        圖片X
        CGFloat imageX = i * imageW;
//        設置frame
        imageView.frame = CGRectMake(imageX, imageY, imageW, imageH);
//        設置圖片
        NSString *name = [NSString stringWithFormat:@"img_0%d", i + 1];
        imageView.image = [UIImage imageNamed:name];
//        隱藏指示條
        self.scrollview.showsHorizontalScrollIndicator = NO;
        
        [self.scrollview addSubview:imageView];
    }
    
//    2.設置scrollview的滾動範圍
    CGFloat contentW = totalCount *imageW;
    //不允許在垂直方向上進行滾動
    self.scrollview.contentSize = CGSizeMake(contentW, 0);
    
//    3.設置分頁
    self.scrollview.pagingEnabled = YES;
    
//    4.監聽scrollview的滾動
    self.scrollview.delegate = self;
    
    [self addTimer];
}

- (void)nextImage
{
    int page = (int)self.pageControl.currentPage;
    if (page == 4) {
        page = 0;
    }else
    {
        page++;
    }
    
//  滾動scrollview
    CGFloat x = page * self.scrollview.frame.size.width;
    self.scrollview.contentOffset = CGPointMake(x, 0);
}

// scrollview滾動的時候調用
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    NSLog(@"滾動中");
//    計算頁碼
//    頁碼 = (contentoffset.x + scrollView一半寬度)/scrollView寬度
    CGFloat scrollviewW =  scrollView.frame.size.width;
    CGFloat x = scrollView.contentOffset.x;
    int page = (x + scrollviewW / 2) /  scrollviewW;
    self.pageControl.currentPage = page;
}

// 開始拖拽的時候調用
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
//    關閉定時器(注意點; 定時器一旦被關閉,無法再開啓)
//    [self.timer invalidate];
    [self removeTimer];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
//    開啓定時器
    [self addTimer];
}

/**
 *  開啓定時器
 */
- (void)addTimer{
    
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(nextImage) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}
/**
 *  關閉定時器
 */
- (void)removeTimer
{
    [self.timer invalidate];
}
@end

提示：以下兩個屬性已經和storyboard中的控件進行了連線。

@property (weak, nonatomic) IBOutletUIScrollView *scrollview;

@property (weak, nonatomic) IBOutletUIPageControl *pageControl;

補充：定時器NSTimer

   定時器 適合用來隔一段時間做一些間隔比較長的操作

 NSTimeInterval:多長多件操作一次

 target :操作誰

 selector : 要操作的方法

 userInfo: 傳遞參數

 repeats: 是否重複

  self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(nextImage) userInfo:nil repeats:YES];