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POChanging a ongoing animation
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copied!<p>Basically, what i'm trying to do is animate a cloud, and then change it's speed and/or direction mid-animation if the wind changes. If it matters, i am controlling the whole thing from a UIViewController, and the cloud exists of a UIView with a CALayer on top of that, which is the cloud itself. I have also tried it with a UIImageView on top.</p> <p>For the TL:DR types, in short what i'm trying to do is either get the position of a animating view, or stop a animating view using block animations.</p> <p>And here's the full story. My problem is to get its position during the animation. I am using block animations. Because i only know the speed with which it should move, i need to calculate the time myself by using the distance left. I have tried the following code, and several variations of it:</p> <pre><code>[[Cloud CloudImage]convertPoint:CGPointMake([[[Cloud CloudImage] presentationLayer] position].x, 0) toLayer:self.layer].x </code></pre> <p>Where Cloud is the UIView and CloudImage is the CALayer. This was the most complex variation i tried of this, i tried various simpler ones (with directly asking the Cloud, for example, or with UIView instead of CALayer). However, all it returns is its final value. I read something about this method being broken from 3.2, but being fixed in 4.2; However, it was not fixed when i changed the deployment target to iOS 4.3 instead of 4.0. I am using the 4.3 base sdk.</p> <p>A few other variations i considered were stopping the animation alltogether for a moment, then getting the position and starting the new animation right away. However, i will need to know a way to stop a block-based animation in its tracks, and i have only found snippets for the older animation system (commitanimations).</p> <p>The last one i considered was writing my own kind of animation system; The cloud would have a repeating NSTimer at 0.08 seconds or so, and create a 0.08 second core animation each time it fired, for which it uses the speed given to the cloud as a property. However, i fear that any variation of this will have much lower performance, while i need it to be as lightweight as possible, for i have up to 20 of these clouds simultaneously (and sometimes with rain too).</p> <p>Thanks in advance!</p>

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