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"
