diff --git a/AnimationRestoration.xcodeproj/project.pbxproj b/AnimationRestoration.xcodeproj/project.pbxproj
index 0553458..afecf5b 100644
--- a/AnimationRestoration.xcodeproj/project.pbxproj
+++ b/AnimationRestoration.xcodeproj/project.pbxproj
@@ -7,6 +7,8 @@
objects = {
/* Begin PBXBuildFile section */
+ 2EA1DA391E96E26B00255843 /* AnimationPreservingView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA1DA381E96E26B00255843 /* AnimationPreservingView.swift */; };
+ 2EA1DA3B1E96E2A700255843 /* ObjectAssociation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA1DA3A1E96E2A700255843 /* ObjectAssociation.swift */; };
2ECCB76F1E96C01F00CD12C6 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2ECCB76E1E96C01F00CD12C6 /* AppDelegate.swift */; };
2ECCB7711E96C01F00CD12C6 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2ECCB7701E96C01F00CD12C6 /* ViewController.swift */; };
2ECCB7741E96C01F00CD12C6 /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 2ECCB7721E96C01F00CD12C6 /* Main.storyboard */; };
@@ -15,6 +17,8 @@
/* End PBXBuildFile section */
/* Begin PBXFileReference section */
+ 2EA1DA381E96E26B00255843 /* AnimationPreservingView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AnimationPreservingView.swift; sourceTree = "<group>"; };
+ 2EA1DA3A1E96E2A700255843 /* ObjectAssociation.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ObjectAssociation.swift; sourceTree = "<group>"; };
2ECCB76B1E96C01F00CD12C6 /* AnimationRestoration.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = AnimationRestoration.app; sourceTree = BUILT_PRODUCTS_DIR; };
2ECCB76E1E96C01F00CD12C6 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
2ECCB7701E96C01F00CD12C6 /* ViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ViewController.swift; sourceTree = "<group>"; };
@@ -54,6 +58,8 @@
2ECCB76D1E96C01F00CD12C6 /* AnimationRestoration */ = {
isa = PBXGroup;
children = (
+ 2EA1DA3A1E96E2A700255843 /* ObjectAssociation.swift */,
+ 2EA1DA381E96E26B00255843 /* AnimationPreservingView.swift */,
2ECCB76E1E96C01F00CD12C6 /* AppDelegate.swift */,
2ECCB7701E96C01F00CD12C6 /* ViewController.swift */,
2ECCB7721E96C01F00CD12C6 /* Main.storyboard */,
@@ -136,7 +142,9 @@
isa = PBXSourcesBuildPhase;
buildActionMask = 2147483647;
files = (
+ 2EA1DA391E96E26B00255843 /* AnimationPreservingView.swift in Sources */,
2ECCB7711E96C01F00CD12C6 /* ViewController.swift in Sources */,
+ 2EA1DA3B1E96E2A700255843 /* ObjectAssociation.swift in Sources */,
2ECCB76F1E96C01F00CD12C6 /* AppDelegate.swift in Sources */,
);
runOnlyForDeploymentPostprocessing = 0;
@@ -301,6 +309,7 @@
2ECCB77F1E96C01F00CD12C6 /* Release */,
);
defaultConfigurationIsVisible = 0;
+ defaultConfigurationName = Release;
};
/* End XCConfigurationList section */
};
diff --git a/AnimationRestoration/AnimationPreservingView.swift b/AnimationRestoration/AnimationPreservingView.swift
new file mode 100644
index 0000000..d80f6d4
--- /dev/null
+++ b/AnimationRestoration/AnimationPreservingView.swift
@@ -0,0 +1,141 @@
+//
+// AnimationPreservingView.swift
+// AnimationPreservingView
+//
+// Created by Wojciech Nagrodzki on 08/03/2017.
+// Copyright © 2017 Wojciech Nagrodzki. All rights reserved.
+//
+
+import UIKit
+
+
+/// The `AnimationPreservingView` class keeps it's layer tree animations safe from being removed.
+/// There are two cases when `CAAnimation` can be removed from `CALayer` automatically:
+/// - when application goes to background
+/// - when view backed by the layer is removed from window
+class AnimationPreservingView: UIView {
+
+ override init(frame: CGRect) {
+ super.init(frame: frame)
+ registerForNotifications()
+ }
+
+ required init?(coder aDecoder: NSCoder) {
+ super.init(coder: aDecoder)
+ registerForNotifications()
+ }
+
+ override func willMove(toWindow newWindow: UIWindow?) {
+ super.willMove(toWindow: newWindow)
+ if newWindow == nil { layer.storeAnimations() }
+ }
+
+ override func didMoveToWindow() {
+ super.didMoveToWindow()
+ if window != nil { layer.restoreAnimations() }
+ }
+}
+
+
+extension AnimationPreservingView {
+
+ fileprivate func registerForNotifications() {
+
+ NotificationCenter.default.addObserver(self,
+ selector: #selector(AnimationPreservingView.applicationWillResignActive),
+ name: .UIApplicationWillResignActive,
+ object: nil)
+ NotificationCenter.default.addObserver(self,
+ selector: #selector(AnimationPreservingView.applicationDidBecomeActive),
+ name: .UIApplicationDidBecomeActive,
+ object: nil)
+ }
+
+ @objc private func applicationWillResignActive() {
+
+ guard window != nil else { return }
+ layer.storeAnimations()
+ }
+
+ @objc private func applicationDidBecomeActive() {
+
+ guard window != nil else { return }
+ layer.restoreAnimations()
+ }
+}
+
+
+extension CALayer {
+
+ private static let association = ObjectAssociation<NSDictionary>()
+
+ private var animationsStorage: [String: CAAnimation] {
+
+ get { return CALayer.association[self] as? [String : CAAnimation] ?? [:] }
+ set { CALayer.association[self] = newValue as NSDictionary }
+ }
+
+ /// Returns a dictionary of copies of animations currently attached to the layer along with their's keys.
+ private var animationsForKeys: [String: CAAnimation] {
+
+ guard let keys = animationKeys() else { return [:] }
+ return keys.reduce([:], {
+ var result = $0
+ let key = $1
+ result[key] = (animation(forKey: key)!.copy() as! CAAnimation)
+ return result
+ })
+ }
+
+ /// Pauses the layer tree and stores it's animations.
+ func storeAnimations() {
+
+ pause()
+ depositAnimations()
+ }
+
+ /// Resumes the layer tree and restores it's animations.
+ func restoreAnimations() {
+
+ withdrawAnimations()
+ resume()
+ }
+
+ private func depositAnimations() {
+
+ animationsStorage = animationsForKeys
+ sublayers?.forEach { $0.depositAnimations() }
+ }
+
+ private func withdrawAnimations() {
+
+ sublayers?.forEach { $0.withdrawAnimations() }
+ animationsStorage.forEach { add($0.value, forKey: $0.key) }
+ animationsStorage = [:]
+ }
+}
+
+
+extension CALayer {
+
+ /// Pauses animations in layer tree.
+ /// - note: [Technical Q&A QA1673](https://developer.apple.com/library/ios/qa/qa1673/_index.html#//apple_ref/doc/uid/DTS40010053)
+ fileprivate func pause() {
+
+ let pausedTime = convertTime(CACurrentMediaTime(), from: nil)
+ speed = 0.0;
+ timeOffset = pausedTime;
+ }
+
+ /// Resumes animations in layer tree.
+ /// - note: [Technical Q&A QA1673](https://developer.apple.com/library/ios/qa/qa1673/_index.html#//apple_ref/doc/uid/DTS40010053)
+ fileprivate func resume() {
+
+ let pausedTime = timeOffset;
+ speed = 1.0;
+ timeOffset = 0.0;
+ beginTime = 0.0;
+ let timeSincePause = convertTime(CACurrentMediaTime(), from: nil) - pausedTime;
+ beginTime = timeSincePause;
+ }
+}
diff --git a/AnimationRestoration/ObjectAssociation.swift b/AnimationRestoration/ObjectAssociation.swift
new file mode 100644
index 0000000..4c0a7e5
--- /dev/null
+++ b/AnimationRestoration/ObjectAssociation.swift
@@ -0,0 +1,55 @@
+//
+// MIT License
+//
+// Copyright (c) 2017 Trifork Kraków Office
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+
+import Foundation
+
+/// Wraps Objective-C runtime object associations. Assumes one instance per association key.
+///
+/// Example usage when simulating stored property with a computed one:
+///
+/// extension SomeType {
+/// private static let association = ObjectAssociation<NSObject>()
+/// var simulatedProperty: NSObject? {
+/// get { return SomeType.association[self] }
+/// set { SomeType.association[self] = newValue }
+/// }
+/// }
+public final class ObjectAssociation<T: AnyObject> {
+
+ private let policy: objc_AssociationPolicy
+
+ /// - Parameter policy: An association policy that will be used when linking objects.
+ public init(policy: objc_AssociationPolicy = .OBJC_ASSOCIATION_RETAIN_NONATOMIC) {
+
+ self.policy = policy
+ }
+
+ /// Accesses associated object.
+ /// - Parameter index: An object whose associated object is to be accessed.
+ public subscript(index: AnyObject) -> T? {
+
+ get { return objc_getAssociatedObject(index, Unmanaged.passUnretained(self).toOpaque()) as! T? }
+ set { objc_setAssociatedObject(index, Unmanaged.passUnretained(self).toOpaque(), newValue, policy) }
+ }
+}