UIView animation to slide down - iphone

Question

I'm trying to slide down an image in an UIImageView, but I don't know which combination of UIContentMode and animation property is the right one to make that happen.
The image should always have the same size and should not be streched... all I want is, that nothing is visible first and then the frame extends and reveals the image.
Maybe it's easier if you see what I mean:
So, it sounds rather easy, but what UIContentMode should I use for the UIImageView and what property should I animate? Thank you!

Answer 1

I took your lead and made a screencast as well. Was this what you had in mind?
I put the animation repeating indefinitely so it would be easier to capture with a video, but it can be started at the press of a button, as well as frozen in place, showing the popover and its contents, until reversed to be hidden again.
I used Core Animation for that, instead of animating a UIView, since I wanted to use the mask property of CALayer to hide the popover and reveal it with a sliding animation.
Here is the code I used (same as in the video):
- (void)viewDidLoad
{
// Declaring the popover layer
CALayer *popover = [CALayer layer];
CGFloat popoverHeight = 64.0f;
CGFloat popoverWidth = 200.0f;
popover.frame = CGRectMake(50.0f, 100.0f, popoverWidth, popoverHeight);
popover.contents = (id) [UIImage imageNamed:#"popover.png"].CGImage;
// Declaring the mask layer
CALayer *maskLayer = [CALayer layer];
maskLayer.frame = CGRectMake(0, - popoverHeight, popoverWidth, popoverHeight);
maskLayer.backgroundColor = [UIColor colorWithRed:1.0f green:1.0f blue:1.0f alpha:1.0f].CGColor;
// Setting the animation (animates the mask layer)
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"position.y"];
animation.byValue = [NSNumber numberWithFloat:popoverHeight];
animation.repeatCount = HUGE_VALF;
animation.duration = 2.0f;
[maskLayer addAnimation:animation forKey:#"position.y"];
//Assigning the animated maskLayer to the mask property of your popover
popover.mask = maskLayer;
[self.view.layer addSublayer:popover];
[super viewDidLoad];
}
NOTE: You have to import the QuartzCore framework into your project and write this line in your header file: #import <QuartzCore/QuartzCore.h>.
Tells if this works for you or if you need any more help setting this up.

Answer 2

Try this code.
Consider the UIImageView as imageView.
imageView.contentMode = UIViewContentModeScaleAspectFill;
CGRect imageRect = imageView.frame;
CGRect origImgRect = imageRect;
imageRect.size.height = 5;
imageView.frame = imageRect;
[UIView animateWithDuration:2.0
animations:^{imageView.rect = origImgRect;}
completion:^(BOOL finished){ }];