Three20通过三种方式加载图片

self.photoSource = [[MockPhotoSource alloc]                        initWithType:MockPhotoSourceNormal                        title:@"Flickr Photos"                        pictures:[[NSArray alloc] initWithObjects:                                  [[[MockPhoto alloc]                                    initWithURL:@"http://farm4.static.flickr.com/3081/3164978791_3c292029f2.jpg?v=0"                                    smallURL:@"documents://xxxx.png"                                    size:CGSizeMake(320, 480)] autorelease]1.@"bundle://pictures/abc/1234.jpg"2.@"documents://xxxx.png"3.@"http://farm4.static.flickr.com/3081/3164978791_3c292029f2.jpg?v=0"