UIActivityIndicatorView

活动指示器的创建：
[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:<#(UIActivityIndicatorViewStyle)#>;  
其中UIActivityIndicatorViewStyle是一个枚举类型，一下为其的三种形式

typedefNS_ENUM(NSInteger, UIActivityIndicatorViewStyle) {
    UIActivityIndicatorViewStyleWhiteLarge,
    UIActivityIndicatorViewStyleWhite,
    UIActivityIndicatorViewStyleGray,
};

    UIActivityIndicatorView *aiv = [[UIActivityIndicatorViewalloc]
initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    [aiv
startAnimating];//活动指示器开始
    [aiv
stopAnimating];//活动指示器停止
    aiv.hidden =
YES;//记得隐藏

网络指示器：

UIApplication *app = [UIApplicationsharedApplication];
    app.networkActivityIndicatorVisible =YES;