import UIKit /// A subclass of `UIImageView` that can be animated using an image name string or raw data. public class AnimatableImageView: UIImageView { /// Proxy object for preventing a reference cycle between the CADisplayLink and AnimatableImageView. /// Source: http://merowing.info/2015/11/the-beauty-of-imperfection/ class TargetProxy { private weak var target: AnimatableImageView? init(target: AnimatableImageView) { self.target = target } @objc func onScreenUpdate() { target?.updateFrame() } } /// An `Animator` instance that holds the frames of a specific image in memory. var animator: Animator? /// A flag to avoid invalidating the displayLink on deinit if it was never created private var displayLinkInitialized: Bool = false /// A display link that keeps calling the `updateFrame` method on every screen refresh. lazy var displayLink: CADisplayLink = { self.displayLinkInitialized = true let display = CADisplayLink(target: TargetProxy(target: self), selector: #selector(TargetProxy.onScreenUpdate)) display.paused = true return display }() /// The size of the frame cache. public var framePreloadCount = 50 /// Specifies whether the GIF frames should be pre-scaled to save memory. Default is **true**. public var needsPrescaling = true /// A computed property that returns whether the image view is animating. public var isAnimatingGIF: Bool { return !displayLink.paused } /// A computed property that returns the total number of frames in the GIF. public var frameCount: Int { return animator?.frameCount ?? 0 } /// Prepares the frames using a GIF image file name, without starting the animation. /// The file name should include the `.gif` extension. /// /// - parameter imageName: The name of the GIF file. The method looks for the file in the app bundle. public func prepareForAnimation(imageNamed imageName: String) { let imagePath = NSBundle.mainBundle().bundleURL.URLByAppendingPathComponent(imageName) guard let data = NSData(contentsOfURL: imagePath) else { return } prepareForAnimation(imageData: data) } /// Prepares the frames using raw GIF image data, without starting the animation. /// /// - parameter data: GIF image data. public func prepareForAnimation(imageData data: NSData) { image = UIImage(data: data) animator = Animator(data: data, size: frame.size, contentMode: contentMode, framePreloadCount: framePreloadCount) animator?.needsPrescaling = needsPrescaling animator?.prepareFrames() attachDisplayLink() } /// Prepares the frames using a GIF image file name and starts animating the image view. /// /// - parameter imageName: The name of the GIF file. The method looks for the file in the app bundle. public func animateWithImage(named imageName: String) { prepareForAnimation(imageNamed: imageName) startAnimatingGIF() } /// Prepares the frames using raw GIF image data and starts animating the image view. /// /// - parameter data: GIF image data. public func animateWithImageData(data: NSData) { prepareForAnimation(imageData: data) startAnimatingGIF() } /// Updates the `image` property of the image view if necessary. This method should not be called manually. override public func displayLayer(layer: CALayer) { image = animator?.currentFrame } /// Starts the image view animation. public func startAnimatingGIF() { if animator?.isAnimatable ?? false { displayLink.paused = false } } /// Stops the image view animation. public func stopAnimatingGIF() { displayLink.paused = true } /// Reset the image view values public func prepareForReuse() { stopAnimatingGIF() animator = nil } /// Update the current frame with the displayLink duration func updateFrame() { if animator?.updateCurrentFrame(displayLink.duration) ?? false { layer.setNeedsDisplay() } } /// Invalidate the displayLink so it releases its target. deinit { if displayLinkInitialized { displayLink.invalidate() } } /// Attaches the display link. func attachDisplayLink() { displayLink.addToRunLoop(.mainRunLoop(), forMode: NSRunLoopCommonModes) } }