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