UILabel * label1 = [[UILabel alloc]initWithFrame:CGRectMake(, , , )];
label1.text = @"qingjoin";
[self.view addSubview:label1]; [UIView beginAnimations:nil context:nil];
[UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
[UIView setAnimationDuration:3.0];
[UIView setAnimationDelegate:self];
label1.alpha =0.0;
[UIView commitAnimations]; //3秒后消失