ios View 淡入淡出效果的代码

- (void)TheAnimation{
     
    animation.delegate = self;
    animation.timingFunction = UIViewAnimationCurveEaseInOut;
     
    NSUInteger f = [[rView subviews] indexOfObject:fView];
    NSUInteger z = [[rView subviews] indexOfObject:zView];
    [rView exchangeSubviewAtIndex:z withSubviewAtIndex:f];
     
    [[rView layer] addAnimation:animation forKey:@"animation"];
     
}