transition between 2 UIImages

I use the code below to transition between two UIImageViews.

-(void)performTransitionNew: (NSInteger)type subType:(NSInteger)subType
                 fromImageView:(UIImageView *)fromImageView
                   toImageView:(UIImageView *)toImageView duration:(NSInteger)duration;
{
    CATransition *transition = [CATransition animation];
    transition.duration = duration;//0.3;
    transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];

    NSString *types[4] = {kCATransitionMoveIn, kCATransitionPush, kCATransitionReveal, kCATransitionFade};
    NSString *subtypes[4] = { kCATransitionFromLeft, kCATransitionFromRight, kCATransitionFromTop, kCATransitionFromBottom};

    transition.type = types[type];

    transition.subtype = subtypes[subType];


    transitioning = YES;
    transition.delegate = self;

    [self.aUIView.layer addAnimation:transition forKey:开发者_高级运维nil];

    fromImageView.hidden = YES;
    toImageView.hidden = NO;

    UIImageView *tmp = toImageView;
    toImageView = fromImageView;
    toImageView = tmp;

}

Both of them are on an UIView 'aUIView'. I want the result to be like this:

but it displays like this:

It looks like toImageView comes from outside of aUIView.

Any comment is welcome.

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The Problem is, that the UIView is on top of the other View (were the slider is) You could change the order of these views. If a UIView is in front of another, the Subviews are also, no matter if they are in the bounds of the parent view or not.