+ Removed position property from the animator delegate method and put…

… it into PagerCollectionViewLayoutAttributes. + Added scrollDirection property to support vertical scrolling. + Added extra properties to support more animation options.
KelvinJin · Feb 22, 2017 · d539aee · d539aee
1 parent 1e24420
commit d539aee
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Showing 10 changed files with 82 additions and 28 deletions.
diff --git a/Source/AnimatedCollectionViewLayout.swift b/Source/AnimatedCollectionViewLayout.swift
@@ -20,36 +20,53 @@ public class AnimatedCollectionViewLayout: UICollectionViewFlowLayout {
 
     public override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
         guard let attributes = super.layoutAttributesForElements(in: rect) else { return nil }
-        return attributes.flatMap { $0.copy() as? UICollectionViewLayoutAttributes }.map { self.transformLayoutAttributes($0) }
+        return attributes.flatMap { $0.copy() as? PagerCollectionViewLayoutAttributes }.map { self.transformLayoutAttributes($0) }
     }
 
-    override public func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
+    public override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
         // We have to return true here so that the layout attributes would be recalculated
         // everytime we scroll the collection view.
         return true
     }
 
-    private func transformLayoutAttributes(_ attributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
+    private func transformLayoutAttributes(_ attributes: PagerCollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
 
-        guard let collectionView = self.collectionView,
-            let a = attributes as? PagerCollectionViewLayoutAttributes else { return attributes }
+        guard let collectionView = self.collectionView else { return attributes }
 
-        // The position for each cell is defined as the ratio of the distance between 
-        // the center of the cell and the center of the screen and the screen width.
-        // It can be negative if the cell is, for instance, on the left of the screen.
+        let a = attributes
 
-        let width = collectionView.frame.width
-        let centerX = width / 2
-        let offset = collectionView.contentOffset.x
-        let itemX = a.center.x - offset
-        let position = (itemX - centerX) / width
+        /** 
+         The position for each cell is defined as the ratio of the distance between
+         the center of the cell and the center of the collectionView and the collectionView width/height
+         depending on the scroll direction. It can be negative if the cell is, for instance,
+         on the left of the screen if you're scrolling horizontally.
+         */
+
+        let distance: CGFloat
+        let itemOffset: CGFloat
+
+        if scrollDirection == .horizontal {
+            distance = collectionView.frame.width
+            itemOffset = a.center.x - collectionView.contentOffset.x
+            a.startOffset = (a.frame.origin.x - collectionView.contentOffset.x) / a.frame.width
+            a.endOffset = (a.frame.origin.x - collectionView.contentOffset.x - collectionView.frame.width) / a.frame.width
+        } else {
+            distance = collectionView.frame.height
+            itemOffset = a.center.y - collectionView.contentOffset.y
+            a.startOffset = (a.frame.origin.y - collectionView.contentOffset.y) / a.frame.height
+            a.endOffset = (a.frame.origin.y - collectionView.contentOffset.y - collectionView.frame.height) / a.frame.height
+        }
+
+        a.scrollDirection = scrollDirection
+        a.middleOffset = itemOffset / distance - 0.5
 
         // Cache the contentView since we're going to use it a lot.
-        if a.contentView == nil {
-            a.contentView = collectionView.cellForItem(at: attributes.indexPath)?.contentView
+        if a.contentView == nil,
+            let c = collectionView.cellForItem(at: attributes.indexPath)?.contentView {
+            a.contentView = c
         }
 
-        animator?.animate(collectionView: collectionView, attributes: a, position: position)
+        animator?.animate(collectionView: collectionView, attributes: a)
 
         return a
     }
@@ -58,10 +75,21 @@ public class AnimatedCollectionViewLayout: UICollectionViewFlowLayout {
 /// A custom layout attributes that contains extra information.
 public class PagerCollectionViewLayoutAttributes: UICollectionViewLayoutAttributes {
     public var contentView: UIView?
+    public var scrollDirection: UICollectionViewScrollDirection = .vertical
+    public var originFrame: CGRect = .zero
+
+    public var startOffset: CGFloat = 0
+    public var middleOffset: CGFloat = 0
+    public var endOffset: CGFloat = 0
 
     public override func copy(with zone: NSZone? = nil) -> Any {
         let copy = super.copy(with: zone) as! PagerCollectionViewLayoutAttributes
         copy.contentView = contentView
+        copy.scrollDirection = scrollDirection
+        copy.originFrame = originFrame
+        copy.startOffset = startOffset
+        copy.middleOffset = middleOffset
+        copy.endOffset = endOffset
         return copy
     }
 }
diff --git a/Source/CrossFadeAttributesAnimator.swift b/Source/CrossFadeAttributesAnimator.swift
@@ -13,7 +13,8 @@ import UIKit
 public struct CrossFadeAttributeAnimator: LayoutAttributesAnimator {
     public init() {}
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         let contentOffset = collectionView.contentOffset
         attributes.frame = CGRect(origin: contentOffset, size: attributes.frame.size)
         attributes.alpha = 1 - abs(position)

diff --git a/Source/CubeAttributesAnimator.swift b/Source/CubeAttributesAnimator.swift
@@ -22,7 +22,8 @@ public struct CubeAttributeAnimator: LayoutAttributesAnimator {
         self.totalAngle = totalAngle
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         if abs(position) >= 1 {
             attributes.contentView?.layer.transform = CATransform3DIdentity
         } else {

diff --git a/Source/LayoutAttributesAnimator.swift b/Source/LayoutAttributesAnimator.swift
@@ -9,5 +9,5 @@
 import UIKit
 
 public protocol LayoutAttributesAnimator {
-    func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat)
+    func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes)
 }
diff --git a/Source/LinearCardAttributesAnimator.swift b/Source/LinearCardAttributesAnimator.swift
@@ -28,7 +28,8 @@ public struct LinearCardAttributeAnimator: LayoutAttributesAnimator {
         self.scaleRate = scaleRate
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         let width = collectionView.frame.width
         let transitionX = -(width * itemSpacing * position)
         let scaleFactor = scaleRate - 0.1 * abs(position)

diff --git a/Source/PageAttributesAnimator.swift b/Source/PageAttributesAnimator.swift
@@ -17,7 +17,8 @@ public struct PageAttributeAnimator: LayoutAttributesAnimator {
         self.scaleRate = scaleRate
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         let contentOffset = collectionView.contentOffset
         let itemOrigin = attributes.frame.origin
         let scaleFactor = scaleRate * min(position, 0) + 1.0

diff --git a/Source/ParallaxAttributesAnimator.swift b/Source/ParallaxAttributesAnimator.swift
@@ -19,14 +19,33 @@ public struct ParallaxAttributesAnimator: LayoutAttributesAnimator {
         self.speed = speed
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
+        let direction = attributes.scrollDirection
+
+        guard let contentView = attributes.contentView else { return }
+
         if abs(position) >= 1 {
             // Reset views that are invisible.
-            attributes.contentView?.transform = .identity
-        } else {
+            contentView.transform = .identity
+        } else if direction == .horizontal {
             let width = collectionView.frame.width
             let transitionX = -(width * speed * position)
-            attributes.contentView?.transform = CGAffineTransform(translationX: transitionX, y: 0)
+            let transform = CGAffineTransform(translationX: transitionX, y: 0)
+            let newFrame = attributes.bounds.applying(transform)
+
+            contentView.frame = newFrame
+        } else {
+            let height = collectionView.frame.height
+            let transitionY = -(height * speed * position)
+            let transform = CGAffineTransform(translationX: 0, y: transitionY)
+
+            // By default, the content view takes all space in the cell
+            let newFrame = attributes.bounds.applying(transform)
+
+            // We don't use transform here since there's an issue if layoutSubviews is called 
+            // for every cell due to layout changes in binding method.
+            contentView.frame = newFrame
         }
     }
 }
diff --git a/Source/RotateInOutAttributesAnimator.swift b/Source/RotateInOutAttributesAnimator.swift
@@ -25,7 +25,8 @@ public struct RotateInOutAttributesAnimator: LayoutAttributesAnimator {
         self.maxRotate = maxRotate
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         if abs(position) >= 1 {
             attributes.contentView?.transform = .identity
             attributes.alpha = 1.0

diff --git a/Source/TurnAttributesAnimator.swift b/Source/TurnAttributesAnimator.swift
@@ -15,7 +15,8 @@ public struct TurnAttributeAnimator: LayoutAttributesAnimator {
         self.perspective = perspective
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         if abs(position) >= 1 {
             attributes.contentView?.layer.transform = CATransform3DIdentity
         } else {

diff --git a/Source/ZoomInOutAttributesAnimator.swift b/Source/ZoomInOutAttributesAnimator.swift
@@ -18,7 +18,8 @@ public struct ZoomInOutAttributesAnimator: LayoutAttributesAnimator {
         self.scaleRate = scaleRate
     }
 
-    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes, position: CGFloat) {
+    public func animate(collectionView: UICollectionView, attributes: PagerCollectionViewLayoutAttributes) {
+        let position = attributes.middleOffset
         if abs(position) >= 1 {
             attributes.contentView?.transform = .identity
         } else {