帧动画

    NSMutableArray *imgArray = [NSMutableArray array];
    for (int i=0; i<4; i++) {
        UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"loading_%d",i+1]];
        [imgArray addObject:image];
    }
    imageView.animationImages=imgArray;
    imageView.animationDuration = 0.5;
    imageView.animationRepeatCount = 0;
    [imageView startAnimating];