Cancel a UIView animation?

Is it possible to cancel a UIView animation while it is in progress? Or would I have to drop to the CA level?

i.e. I've done something like this (maybe setting an end animation action too):

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:duration];
[UIView setAnimationCurve: UIViewAnimationCurveLinear];
// other animation properties

// set view properties

[UIView commitAnimations];

But before the animation completes and I get the animation ended event, I want to cancel it (cut it short). Is this possible? Googling around finds a few people asking the same question with no answers - and one or two people speculating that it can't be done.

Use:

#import <QuartzCore/QuartzCore.h>

.......

[myView.layer removeAllAnimations];

The way I do it is to create a new animation to your end point. Set a very short duration and make sure you use the +setAnimationBeginsFromCurrentState: method to start from the current state. When you set it to YES, the current animation is cut short. Looks something like this:

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:0.1];
[UIView setAnimationCurve: UIViewAnimationCurveLinear];
// other animation properties

// set view properties

[UIView commitAnimations];

Simplest way to stop all animations on a particular view, immediately, is this:

Link the project to QuartzCore.framework. At the start of your code:

#import <QuartzCore/QuartzCore.h>

Now, when you want to stop all animations on a view dead in their tracks, say this:

[CATransaction begin];
[theView.layer removeAllAnimations];
[CATransaction commit];

The middle line would work all by itself, but there's a delay until the runloop finishes (the "redraw moment"). To prevent that delay, wrap the command in an explicit transaction block as shown. This works provided no other changes have been performed on this layer in the current runloop.

On iOS 4 and greater, use the UIViewAnimationOptionBeginFromCurrentState option on the second animation to cut the first animation short.

As an example, assume you have a view with an activity indicator. You wish to fade in the activity indicator while some potentially time consuming activity begins, and fade it out when the activity is finished. In the code below, the view with the activity indicator on it is called activityView.

- (void)showActivityIndicator {
    activityView.alpha = 0.0;
    activityView.hidden = NO;
    [UIView animateWithDuration:0.5
                 animations:^(void) {
                     activityView.alpha = 1.0;
                 }];

- (void)hideActivityIndicator {
    [UIView animateWithDuration:0.5
                 delay:0 options:UIViewAnimationOptionBeginFromCurrentState
                 animations:^(void) {
                     activityView.alpha = 0.0;
                 }
                 completion:^(BOOL completed) {
                     if (completed) {
                         activityView.hidden = YES;
                     }
                 }];
}