渐变式切换图片

ViewController.h

@interface ViewController : UIViewController<UIScrollViewDelegate>
{

    UIImageView *imageView1;
    UIImageView *imageView2;
}

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIScrollView *scrollerView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 20, 320, 460)];
    scrollerView.pagingEnabled = YES;
    scrollerView.delegate = self;
    scrollerView.backgroundColor = [UIColor clearColor];
    scrollerView.contentSize = CGSizeMake(320*2, 460);
    
    [self.view addSubview:scrollerView];
    
    imageView1 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"0"]];
    imageView1.frame = CGRectMake(0, 20, 320, 460);
    imageView1.alpha = 1;
    [self.view addSubview:imageView1];
    
    imageView2 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"1"]];
    imageView2.frame = CGRectMake(0, 20, 320, 460);
    imageView2.alpha = 0;
    [self.view addSubview:imageView2];
    
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {

    imageView1.alpha = 1 - scrollView.contentOffset.x/320;
    imageView2.alpha = scrollView.contentOffset.x/320;
    
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end