SDWebImage-FadeInFadeOut

SDWebImage-FadeInFadeOut / 图片缓存 淡入淡出效果

只有当此图片没有缓存时，下载后显示时 展示淡入淡出效果

- (void)sd_setImageFIFOWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholde;

//duration 动画时间
- (void)sd_setImageFIFOWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder animateWithDuration:(CGFloat)duration;

- (void)sd_setImageFIFOWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder options:(SDWebImageOptions)options animateWithDuration:(CGFloat)duration;

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####效果图(如下):