HUB的offSetY属性在Y轴上的原点为屏幕Y轴方向上的中间位置，offSetY为正数时，Hub在中间位置的下方，负数时再中间位置的上方。

#pragma mark --枚举，消息提示框的位置typedef NS_ENUM(NSInteger,MBProgressHUBPosition) {    MBProgressHUBPositionTop,            //头部    MBProgressHUBPositionCenter,         //中心    MBProgressHUBPositionBottom          //底部};

#pragma mark --消息提示框+ (void)showAlertMessage:(NSString *)message toView:(UIView *)view position:(MBProgressHUBPosition)position {    [MBProgressHUD hide];    if (view == nil) {        view = [UIApplication sharedApplication].keyWindow;    }    MBProgressHUD *hub = [MBProgressHUD showHUDAddedTo:view animated:YES];    hub.userInteractionEnabled = NO;    hub.mode = MBProgressHUDModeText;    hub.labelText = message;    hub.animationType = MBProgressHUDAnimationZoomIn;    hub.margin = 10.f;    hub.opacity = 0.2;    CGFloat margin = 92 ;  //距离底部和顶部的距离    CGFloat offSetY = view.bounds.size.height / 2 - margin;    if (position == MBProgressHUBPositionTop) {        hub.yOffset = -offSetY;    }    if (position == MBProgressHUBPositionCenter) {        hub.yOffset = 0;    }    if (position == MBProgressHUBPositionBottom) {        hub.yOffset = offSetY;    }    [hub hide:YES afterDelay:2.0];}