翻转动画忽略了持续时间，即我无法控制速度

[UIView animateWithDuration:15.0 
    animations:^(void) {
        cardOne.center =CGPointMake(100, 100);
        cardTwo.center =CGPointMake(100, 100);

        //low level calls, to directly perform the image swap 
        [cardOne.face removeFromSuperview]; 
        [cardOne addSubview:cardOne.back];
        [cardOne sendSubviewToBack:cardOne.face]; 

        //calling the transitionFromView to do the image swap
        [UIView transitionFromView:cardOne.face 
                            toView:cardOne.back 
                          duration:10 
                           options:UIViewAnimationTransitionFlipFromLeft 
                        completion:^(BOOL finished){ }];

/*  
[UIView animateWithDuration:animationDuration  
animations:^{  
    [self.face removeFromSuperview];    
    [self addSubview:self.back];  
    [self sendSubviewToBack:self.face];              
}];  
*/

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:kDefaultFlipSpeed];
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft
                               forView:self
                                 cache:YES];

[self.face removeFromSuperview];
[self addSubview:self.back];
[self sendSubviewToBack: self.face];

[UIView commitAnimations];