- (void)viewDidLoad {    [super viewDidLoad];        self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"清除缓存" style:UIBarButtonItemStylePlain target:self action:@selector(clearCache)];         // 获取SDwebImage图片所占的磁盘容量大小(以byte为单位)    NSUInteger byteSize = [SDImageCache sharedImageCache].getSize;    double size = byteSize / 1000.0 / 1000.0; // mac和ios系统在byte和kb之前互转时，比是1000；        self.navigationItem.title = [NSString stringWithFormat:@"缓存%.1fM",size];}// 清除缓存- (void)clearCache {    // 创建一个小菊花    UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:indicator];    [indicator startAnimating];        // 清空SDWebImage缓存图片    [[SDImageCache sharedImageCache] clearDisk];        self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"清除缓存" style:UIBarButtonItemStylePlain target:self action:@selector(clearCache)];    self.navigationItem.title = @"缓存0M";}

最终效果：