- (void)viewDidLoad{    [super viewDidLoad];    // Do any additional setup after loading the view.            UIImageView *img=[[UIImageView alloc]initWithFrame:CGRectMake(50, 100, 200, 200)];    img.backgroundColor=[UIColor redColor];    [self.view addSubview:img];            //从网络下载图片，保存，并用 UIImageView 从保存中显示    NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];    NSLog(@"保存路径:%@",documentsDirectoryPath);            //Get Image From URL    UIImage * imageFromURL = [self getImageFromURL:@"http://file.duteba.com/phone/2009/04/5/ftGxL8kcUL.jpg"];            //Save Image to Directory    [self saveImage:imageFromURL withFileName:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];            //Load Image From Directory    UIImage * imageFromWeb = [self loadImage:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];    [img setImage:imageFromWeb];            //取得目录下所有文件名    NSArray *file = [[[NSFileManager alloc] init] subpathsAtPath:documentsDirectoryPath];    NSLog(@"%d",[file count]);    NSLog(@"%@",file);    }//从网络下载图片-(UIImage *) getImageFromURL:(NSString *)fileURL {    NSLog(@"执行图片下载函数");    UIImage * result;        NSData * data =http://www.mamicode.com/ [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];    result = [UIImage imageWithData:data];        return result;}//将所下载的图片保存到本地-(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {    if ([[extension lowercaseString] isEqualToString:@"png"]) {        [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];    } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {        [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];    } else {        //ALog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);        NSLog(@"文件后缀不认识");    }}//读取本地保存的图片-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {    UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];        return result;}