将VIew移动做成动画效果    这种动画效果没有中间的位移

可以添加动画的View属性center，frame，alpha，transform , backgroundColor

//继续做消失的动画

[UIView animateWithDuration:1 animations:^{

iv.alpha = 0;

} completion:^(BOOL finished) {

            //完成动画后执行 可以继续添加

[iv removeFromSuperview];

}];

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(addSnow) userInfo:nil repeats:YES];

}

-(void)addSnow{

int size = arc4random()%10+10;

UIImageView *iv = [[UIImageViewalloc]initWithFrame:CGRectMake(arc4random()%(320-size), -size, size, size)];

iv.p_w_picpath = [UIImagep_w_picpathNamed:@"snow"];

[self.view addSubview:iv];

int time = arc4random()%4+1;

    //添加移动动画

[UIView animateWithDuration:time animations:^{

        //移动的终点位置

iv.center = CGPointMake(iv.center.x, 568);

        //图形改变终点形状

iv.transform = CGAffineTransformRotate(iv.transform, (arc4random()%360)/180.0*M_PI);

} completion:^(BOOLfinished) {

        //继续做雪花消失的动画

[UIView animateWithDuration:1 animations:^{

iv.alpha = 0;

} completion:^(BOOL finished) {

[iv removeFromSuperview];

}];

}];

}