Gifu/Source/Classes/Animator.swift

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Swift
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import UIKit
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/// Responsible for parsing GIF data and decoding the individual frames.
public class Animator {
/// Total duration of one animation loop
var loopDuration: TimeInterval {
return frameStore?.loopDuration ?? 0
}
/// Number of frame to buffer.
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var frameBufferCount = 50
/// Specifies whether GIF frames should be resized.
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var shouldResizeFrames = false
/// Responsible for loading individual frames and resizing them if necessary.
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var frameStore: FrameStore?
/// Tracks whether the display link is initialized.
private var displayLinkInitialized: Bool = false
/// A delegate responsible for displaying the GIF frames.
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private weak var delegate: GIFAnimatable!
/// Responsible for starting and stopping the animation.
private lazy var displayLink: CADisplayLink = { [unowned self] in
self.displayLinkInitialized = true
let display = CADisplayLink(target: DisplayLinkProxy(target: self), selector: #selector(DisplayLinkProxy.onScreenUpdate))
display.isPaused = true
return display
}()
/// Introspect whether the `displayLink` is paused.
var isAnimating: Bool {
return !displayLink.isPaused
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}
/// Total frame count of the GIF.
var frameCount: Int {
return frameStore?.frameCount ?? 0
}
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/// Creates a new animator with a delegate.
///
/// - parameter view: A view object that implements the `GIFAnimatable` protocol.
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///
/// - returns: A new animator instance.
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public init(withDelegate delegate: GIFAnimatable) {
self.delegate = delegate
}
/// Checks if there is a new frame to display.
fileprivate func updateFrameIfNeeded() {
guard let store = frameStore else { return }
if store.isFinished {
stopAnimating()
return
}
store.shouldChangeFrame(with: displayLink.duration) {
if $0 { delegate.animatorHasNewFrame() }
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}
}
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/// Prepares the animator instance for animation.
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///
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/// - parameter imageName: The file name of the GIF in the main bundle.
/// - parameter size: The target size of the individual frames.
/// - parameter contentMode: The view content mode to use for the individual frames.
/// - parameter loopCount: Desired number of loops, <= 0 for infinite loop.
/// - parameter completionHandler: Completion callback function
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func prepareForAnimation(withGIFNamed imageName: String, size: CGSize, contentMode: UIViewContentMode, loopCount: Int = 0, completionHandler: (() -> Void)? = nil) {
guard let extensionRemoved = imageName.components(separatedBy: ".")[safe: 0],
let imagePath = Bundle.main.url(forResource: extensionRemoved, withExtension: "gif"),
let data = try? Data(contentsOf: imagePath) else { return }
prepareForAnimation(withGIFData: data,
size: size,
contentMode: contentMode,
loopCount: loopCount,
completionHandler: completionHandler)
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}
/// Prepares the animator instance for animation.
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///
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/// - parameter imageData: GIF image data.
/// - parameter size: The target size of the individual frames.
/// - parameter contentMode: The view content mode to use for the individual frames.
/// - parameter loopCount: Desired number of loops, <= 0 for infinite loop.
/// - parameter completionHandler: Completion callback function
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func prepareForAnimation(withGIFData imageData: Data, size: CGSize, contentMode: UIViewContentMode, loopCount: Int = 0, completionHandler: (() -> Void)? = nil) {
frameStore = FrameStore(data: imageData,
size: size,
contentMode: contentMode,
framePreloadCount: frameBufferCount,
loopCount: loopCount)
frameStore!.shouldResizeFrames = shouldResizeFrames
frameStore!.prepareFrames(completionHandler)
attachDisplayLink()
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}
/// Add the display link to the main run loop.
private func attachDisplayLink() {
displayLink.add(to: .main, forMode: RunLoopMode.commonModes)
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}
deinit {
if displayLinkInitialized {
displayLink.invalidate()
}
}
/// Start animating.
func startAnimating() {
if frameStore?.isAnimatable ?? false {
displayLink.isPaused = false
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}
}
/// Stop animating.
func stopAnimating() {
displayLink.isPaused = true
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}
/// Prepare for animation and start animating immediately.
///
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/// - parameter imageName: The file name of the GIF in the main bundle.
/// - parameter size: The target size of the individual frames.
/// - parameter contentMode: The view content mode to use for the individual frames.
/// - parameter loopCount: Desired number of loops, <= 0 for infinite loop.
/// - parameter completionHandler: Completion callback function
func animate(withGIFNamed imageName: String, size: CGSize, contentMode: UIViewContentMode, loopCount: Int = 0, completionHandler: (() -> Void)? = nil) {
prepareForAnimation(withGIFNamed: imageName,
size: size,
contentMode: contentMode,
loopCount: loopCount,
completionHandler: completionHandler)
startAnimating()
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}
/// Prepare for animation and start animating immediately.
///
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/// - parameter imageData: GIF image data.
/// - parameter size: The target size of the individual frames.
/// - parameter contentMode: The view content mode to use for the individual frames.
/// - parameter loopCount: Desired number of loops, <= 0 for infinite loop.
/// - parameter completionHandler: Completion callback function
func animate(withGIFData imageData: Data, size: CGSize, contentMode: UIViewContentMode, loopCount: Int = 0, completionHandler: (() -> Void)? = nil) {
prepareForAnimation(withGIFData: imageData,
size: size,
contentMode: contentMode,
loopCount: loopCount,
completionHandler: completionHandler)
startAnimating()
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}
/// Stop animating and nullify the frame store.
func prepareForReuse() {
stopAnimating()
frameStore = nil
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}
/// Gets the current image from the frame store.
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///
/// - returns: An optional frame image to display.
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func activeFrame() -> UIImage? {
return frameStore?.currentFrameImage
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}
}
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/// A proxy class to avoid a retain cycle with the display link.
fileprivate class DisplayLinkProxy {
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/// The target animator.
private weak var target: Animator?
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/// Create a new proxy object with a target animator.
///
/// - parameter target: An animator instance.
///
/// - returns: A new proxy instance.
init(target: Animator) { self.target = target }
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/// Lets the target update the frame if needed.
@objc func onScreenUpdate() { target?.updateFrameIfNeeded() }
}