从网络下载图片，保存，并用 UIImageView 从保存中显示

//从网络下载图片
-(UIImage ) getImageFromURL:(NSString )fileURL {
    NSLog(@"执行图片下载函数");
    UIImage * result;

NSData * data = [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;

}
//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);</pre>