- (void)viewDidLoad{    [super viewDidLoad];    // Do any additional setup after loading the view.        UIScrollView * sv = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];    sv.contentSize = CGSizeMake(320 * 4, 460);    sv.pagingEnabled = YES;    sv.showsHorizontalScrollIndicator = NO;    sv.delegate = self;    sv.tag = 1;    [self.view addSubview:sv];        UIPageControl * pc = [[UIPageControl alloc] initWithFrame:CGRectMake(0, 420, 320, 20)];    pc.numberOfPages = 4;    [pc addTarget:self action:@selector(pc:) forControlEvents:UIControlEventTouchUpInside];    pc.tag = 2;    [self.view addSubview:pc];        for(int i = 0; i < 4; i++){        UIImageView * imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[NSString stringWithFormat:@"start%d.png",i+1]]];        imageView.frame = CGRectMake(320 * i, 0, 320, 460);        [sv addSubview:imageView];    }        UIButton * button = [UIButton buttonWithType:UIButtonTypeCustom];    button.frame = CGRectMake(320*3+100, 380, 164, 42);    [button setImage:[UIImage imageNamed:@"anniu.png"] forState:UIControlStateNormal];    [button addTarget:self action:@selector(start) forControlEvents:UIControlEventTouchUpInside];    [sv addSubview:button];}#pragma -mark -doClickAction-(void)pc:(UIPageControl *)pc{    UIScrollView * sv = (UIScrollView *)[self.view viewWithTag:1];    sv.contentOffset = CGPointMake(pc.currentPage*320, 0);}-(void)start{    UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"开始" message:nil delegate:self cancelButtonTitle:@"知道了" otherButtonTitles:nil, nil];    [alert show];}#pragma -mark -UISCrollerViewDelegate-(void)scrollViewDidScroll:(UIScrollView *)scrollView{    UIPageControl * pc = (UIPageControl *)[self.view viewWithTag:2];    pc.currentPage = scrollView.contentOffset.x/320;}