131 lines
4.4 KiB
Swift
131 lines
4.4 KiB
Swift
import UIKit
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/// A subclass of `UIImageView` that can be animated using an image name string or raw data.
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public class AnimatableImageView: UIImageView {
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/// Proxy object for preventing a reference cycle between the CADisplayLink and AnimatableImageView.
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/// Source: http://merowing.info/2015/11/the-beauty-of-imperfection/
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fileprivate class TargetProxy {
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private weak var target: AnimatableImageView?
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init(target: AnimatableImageView) {
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self.target = target
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}
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@objc func onScreenUpdate() {
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target?.updateFrameIfNeeded()
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}
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}
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/// An `Animator` instance that holds the frames of a specific image in memory.
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var animator: Animator?
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/// A flag to avoid invalidating the displayLink on deinit if it was never created
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private var displayLinkInitialized: Bool = false
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/// A display link that keeps calling the `updateFrame` method on every screen refresh.
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lazy var displayLink: CADisplayLink = { [unowned self] in
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self.displayLinkInitialized = true
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let display = CADisplayLink(target: TargetProxy(target: self), selector: #selector(TargetProxy.onScreenUpdate))
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display.isPaused = true
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return display
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}()
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/// The size of the frame cache.
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public var framePreloadCount = 50
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/// Specifies whether the GIF frames should be pre-scaled to save memory. Default is **true**.
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public var needsPrescaling = true
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/// A computed property that returns whether the image view is animating.
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public var isAnimatingGIF: Bool {
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return !displayLink.isPaused
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}
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/// A computed property that returns the total number of frames in the GIF.
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public var frameCount: Int {
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return animator?.frameCount ?? 0
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}
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/// Prepares the frames using a GIF image file name, without starting the animation.
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/// The file name should include the `.gif` extension.
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///
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/// - parameter imageName: The name of the GIF file. The method looks for the file in the app bundle.
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public func prepareForAnimation(withGIFNamed imageName: String) {
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guard let extensionRemoved = imageName.components(separatedBy: ".")[safe: 0],
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let imagePath = Bundle.main.url(forResource: extensionRemoved, withExtension: "gif"),
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let data = try? Data(contentsOf: imagePath) else { return }
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prepareForAnimation(withGIFData: data)
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}
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/// Prepares the frames using raw GIF image data, without starting the animation.
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///
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/// - parameter data: GIF image data.
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public func prepareForAnimation(withGIFData imageData: Data) {
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image = UIImage(data: imageData)
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animator = Animator(data: imageData, size: frame.size, contentMode: contentMode, framePreloadCount: framePreloadCount)
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animator?.needsPrescaling = needsPrescaling
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animator?.prepareFrames()
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attachDisplayLink()
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}
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/// Prepares the frames using a GIF image file name and starts animating the image view.
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///
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/// - parameter imageName: The name of the GIF file. The method looks for the file in the app bundle.
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public func animate(withGIFNamed imageName: String) {
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prepareForAnimation(withGIFNamed: imageName)
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startAnimatingGIF()
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}
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/// Prepares the frames using raw GIF image data and starts animating the image view.
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///
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/// - parameter data: GIF image data.
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public func animate(withGIFData data: Data) {
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prepareForAnimation(withGIFData: data)
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startAnimatingGIF()
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}
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/// Updates the `image` property of the image view if necessary. This method should not be called manually.
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override public func display(_ layer: CALayer) {
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image = animator?.currentFrameImage ?? image
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}
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/// Starts the image view animation.
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public func startAnimatingGIF() {
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if animator?.isAnimatable ?? false {
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displayLink.isPaused = false
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}
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}
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/// Stops the image view animation.
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public func stopAnimatingGIF() {
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displayLink.isPaused = true
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}
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/// Reset the image view values.
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public func prepareForReuse() {
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stopAnimatingGIF()
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animator = nil
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}
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/// Update the current frame if needed.
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func updateFrameIfNeeded() {
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guard let animator = animator else { return }
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animator.shouldChangeFrame(with: displayLink.duration) { hasNewFrame in
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if hasNewFrame { self.layer.setNeedsDisplay() }
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}
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}
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/// Invalidate the displayLink so it releases its target.
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deinit {
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if displayLinkInitialized {
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displayLink.invalidate()
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}
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}
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/// Attaches the display link.
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func attachDisplayLink() {
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displayLink.add(to: .main, forMode: RunLoopMode.commonModes)
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}
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}
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