//（1）將需要展⽰的內容添加到UIScrollView中
//（2）設置UIScrollView的contentSize屬性,告訴UIScrollView所有內容的尺寸,也就是告訴 它滾動的范圍(能滾多遠,滾到哪⾥是盡頭)
#define imageCount 5
#import "ViewController.h"
 
@interface ViewController ()<UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@property (weak, nonatomic) IBOutlet UIPageControl *pageControl;
@property(nonatomic,strong)NSTimer *timer;
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad
{
 [super viewDidLoad];
 //1.添加5張圖片到scrollView中
 //設置圖片frame,尺寸與scrollView一樣高
 CGFloat imageW=self.scrollView.frame.size.width;
 CGFloat imageH=self.scrollView.frame.size.height;
 //圖片的具體位置需要動態計算
 CGFloat imageY=0;
 for (int i=0; i<imageCount; i++)
 {
  UIImageView *imageView=[[UIImageView alloc]init];
  CGFloat imageX=i*imageW;
  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];
  
  [self.scrollView addSubview:imageView];
 }
 
 //2.設置滾動內容的尺寸
 CGFloat contentW=5*imageW;
 self.scrollView.contentSize=CGSizeMake(contentW, 0);
 
 //3.隱藏水平的滾動條
 self.scrollView.showsHorizontalScrollIndicator=NO;
 
 //4.分頁
 self.pageControl.enabled=YES;
 
 //5.設置代理
 self.scrollView.delegate=self;
 
 //6.設置pageControl的總頁數
 self.pageControl.numberOfPages=imageCount;
 
 //7.添加定時器
 self.timer=[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextImage) userInfo:nil repeats:YES];
 [[NSRunLoop currentRunLoop]addTimer:self.timer forMode:NSRunLoopCommonModes];
}
-(void)nextImage
{
 int page=0;
 if(self.pageControl.currentPage==imageCount-1)
 {
  //如果滾動到最后一頁了，那下一頁就是第一頁
  page=0;
 }
 else
 {
  //否則就是下一頁
  page=(int)self.pageControl.currentPage+1;
 }
 
 //2.計算scrollView滾動的位置
 CGFloat offsetX=page*self.scrollView.frame.size.width;
 CGPoint offset=CGPointMake(offsetX, 0);
 [self.scrollView setContentOffset:offset animated:YES];
}
 
//開始拖拽的時候調用
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
 //停止定時器
 [self.timer invalidate];
 self.timer=nil;
}
 
//停止拖拽的時候調用
-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
 //再次開啟定時器
 self.timer=[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextImage) userInfo:nil repeats:YES];
 [[NSRunLoop currentRunLoop]addTimer:self.timer forMode:NSRunLoopCommonModes];
 
}
//當scrollView正在滾動就會調用
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
 //根據scrollView的滾動位置決定pageControl顯示第幾頁
 int page=(scrollView.contentOffset.x+self.scrollView.frame.size.width*0.5)/scrollView.frame.size.width;
 self.pageControl.currentPage=page;
}