UIActivityIndicatorView

//活动指示视图
UIActivityIndicatorView *flower1 = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

//活动指示圈
UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:(UIActivityIndicatorViewStyleWhiteLarge)];
activityIndicator.frame = CGRectMake(70, 200, 200, 200);
activityIndicator.backgroundColor = [UIColor blackColor];

// 开始活动
[activityIndicator startAnimating];

// 结束活动
[activityIndicator stopAnimating];