以动画的形式让label等出现消失等

        [UIView animateWithDuration:1.0 animations:^{
            label.alpha=1.0;
        } completion:^(BOOL finished) {
            
            [UIView animateWithDuration:1.0 animations:^{
                label.alpha=0.0;
            } completion:^(BOOL finished) {
                
                [label removeFromSuperview];
                
            }];
        }];

/*

animateWithDuration:持续的时间

animations:^{} :在这个持续的时间内需要完成的事情

animations:^{}：事件完成后进行的操作

*/