1.面试题
1> 如何防止一个url对应的图片重复下载
* “cell下载图片思路 – 有沙盒缓存”
2> SDWebImage的默认缓存时长是多少？
* 1个星期
3> SDWebImage底层是怎么实现的？
* 上课PPT的“cell下载图片思路 – 有沙盒缓存”
2.SDWebImage
1> 常用方法
- (void)sd_setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder;
- (void)sd_setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder options:(SDWebImageOptions)options;
- (void)sd_setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder completed:(SDWebImageCompletionBlock)completedBlock;
- (void)sd_setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletionBlock)completedBlock;
2> 内存处理：当app接收到内存警告时
/**
* 当app接收到内存警告
*/
- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application
{
SDWebImageManager *mgr = [SDWebImageManager sharedManager];
// 1.取消正在下载的操作
[mgr cancelAll];
// 2.清除内存缓存
[mgr.imageCache clearMemory];
}
3> SDWebImageOptions
* SDWebImageRetryFailed : 下载失败后，会自动重新下载
* SDWebImageLowPriority : 当正在进行UI交互时，自动暂停内部的一些下载操作
* SDWebImageRetryFailed | SDWebImageLowPriority : 拥有上面2个功能