Easy UIView Animations! Frame, Alpha and more!

[mxweas]

Some nice functionality UIView has, is the ability to animate different properties of UIView's and their subclass's. The basic idea is to tell UIView to setup for animations, then change a property or two on any number of views, and finish up the animation. Heres a quick example of animating a view to slide in from the right side of the screen.

CGRect rect = [ [ UIScreen mainScreen ] applicationFrame ];
rect.origin.x = rect.size.width; // move the rect off the screen.
UIView *myViewIWantToAnimate = [ [ UIView alloc ] initWithFrame: rect ]; // Initialize the view off to the right of the screen.

[ UIView beginAnimations: nil context: @"some-identifier-used-by-a-delegate-if-set" ]; // Tell UIView we're ready to start animations.
[ UIView setAnimationDelegate: self ]; // Set the delegate (Only needed if you need to use the animationDid... selectors)
[ UIView setAnimationDidStopSelector: @selector(animationDidStop:finished:context:) ]; // example of a selector called with context when animation finishes.
[ UIView setAnimationCurve: UIViewAnimationCurveEaseInOut ];
[ UIView setAnimationDuration: 0.4f ]; // Set the duration to 4/10ths of a second.

CGRect tempFrame = myViewIWantToAnimate.frame; // Get the current frame.
tempFrame.origin.x = 0.0f // Move the view completely on screen.
myViewThatIWantToAnimate.frame = tempFrame; // set the new frame

[ UIView commitAnimations ]; // Animate!

Thats it!, you can animate multiple views at the same time, and this method works with almost all UIView properties.

Max

[bainfu]

UIView animations and transformations are fun. I have been looking for a way to stagger animations, do you think having a reoccurring thread and a animation action stack is the way to go, or is there something built into Cocoa Touch?

[optimo]

something with timers...
or performSelectorAfterDelay

[mxweas]

If you wanted to do something like animate a view down and back up you could do something like this:

CGRect rect = CGRectMake(0.0f, 0.0f, 320.0f, 100.0f);
UIView *myViewIWantToAnimate = [ [ UIView alloc ] initWithFrame: rect ]; // Make the view.
myViewIWantToAnimate.backgroundColor = [ UIColor blueColor ]; // Set the background color blue.

/* Animate the view down 60 pixels */
[ UIView beginAnimations: nil context: nil ]; // Tell UIView we're ready to start animations.
[ UIView setAnimationCurve: UIViewAnimationCurveEaseInOut ];
[ UIView setAnimationDuration: 1.0f ]; // Set the duration to 1 second.
myViewIWantToAnimate.frame = CGRectMake(rect.origin.x, rect.origin.y + 60.0f, rect.size.width, rect.size.height); // Set the frame 60 pixels down.
[ UIView commitAnimations ]; // Animate!

/* Animate the view back to it's original spot on the screen */
[ UIView beginAnimations: nil context: nil ]; // Tell UIView we're ready to start animations.
[ UIView setAnimationCurve: UIViewAnimationCurveEaseInOut ];
[ UIView setAnimationDuration: 1.0f ]; // Set the duration to 1 second.
myViewIWantToAnimate.frame = rect; // Set the frame to the original frame.
[ UIView commitAnimations ]; // Animate!

Max

[lvsti]

I'd spent two hours trying to reposition a frame with UIView's animation until I realized that this code won't work:

[UIView beginAnimations:nil context:NULL];
myView.frame.origin.y = aNewOriginY;
[UIView commitAnimations];

So, to remedy others from wasting their time, I'd like to point out that the property to be changed should always be set AS A WHOLE to get the transition work:

[UIView beginAnimations:nil context:NULL];
CGRect newFrame = myView.frame;
newFrame.origin.y = aNewOriginY;
myView.frame = newFrame;
[UIView commitAnimations];

Hope someone will find this useful.