iOS 動畫效果。簡單的提示消失

 UILabel  * label1 = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, 320, 30)];
    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