下载网络图片到图库

 代码介绍：首先开启一个线程请求网络图片，图片下载成功之后保存到相册中。代码简单易懂。

@implementation ViewController

{

       NSData *data;

}

- (void)viewDidLoad {

    [super viewDidLoad];

 

    

    UIImageView *imageview=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 300, 200)];

    [imageview setBackgroundColor:[UIColor grayColor]];

     [self.view addSubview:imageview];

    

    dispatch_async(dispatch_get_global_queue(0, 0), ^{

         data=[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://image.baidu.com/search/down?tn=download&word=download&ie=utf8&fr=detail&url=http%3A%2F%2Fpic26.nipic.com%2F20121223%2F9252150_195341264315_2.jpg&thumburl=http%3A%2F%2Fimg3.imgtn.bdimg.com%2Fit%2Fu%3D806135425%2C801140138%26fm%3D21%26gp%3D0.jpg"]];

        dispatch_async(dispatch_get_main_queue(), ^{

            

           [imageview setImage:[UIImage imageWithData:data]];

            UIImageWriteToSavedPhotosAlbum(imageview.image, self, @selector(imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), nil);

            

            

            NSLog(@"下载完成1");

        });

        NSLog(@"下载完成2");

    });

    NSLog(@"下载完成3");

}

- (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo

{

    NSString *message = @"呵呵";

    if (!error) {

        message = @"成功保存到相册";

    }else

    {

        message = [error description];

    }

    NSLog(@"message is %@",message);

}