Gifu/Source/AnimatableImageView.swift

123 lines
4.0 KiB
Swift

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 display link that keeps calling the `updateFrame` method on every screen refresh.
lazy var displayLink: CADisplayLink = {
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)
prepareForAnimation <^> NSData(contentsOfURL: imagePath)
}
/// 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 {
// invalidate will also remove the link from all run loops
displayLink.invalidate()
}
/// Attaches the display link.
func attachDisplayLink() {
displayLink.addToRunLoop(.mainRunLoop(), forMode: NSRunLoopCommonModes)
}
}