fix & feat: maintain equal spacing between page indicators and add option to disable item position adjustment for multiple items

FSPageViewExample-Swift/FSPagerViewExample/BasicExampleViewController.swift

@@ -11,7 +11,7 @@ import UIKit
 class BasicExampleViewController: UIViewController,UITableViewDataSource,UITableViewDelegate,FSPagerViewDataSource,FSPagerViewDelegate {
 
     fileprivate let sectionTitles = ["Configurations", "Decelaration Distance", "Item Size", "Interitem Spacing", "Number Of Items"]
-    fileprivate let configurationTitles = ["Automatic sliding","Infinite"]
+    fileprivate let configurationTitles = ["Automatic sliding","Infinite","itemAdjust"]
     fileprivate let decelerationDistanceOptions = ["Automatic", "1", "2"]
     fileprivate let imageNames = ["1.jpg","2.jpg","3.jpg","4.jpg","5.jpg","6.jpg","7.jpg"]
     fileprivate var numberOfItems = 7
@@ -63,6 +63,9 @@ class BasicExampleViewController: UIViewController,UITableViewDataSource,UITable
             } else if indexPath.row == 1 {
                 // IsInfinite
                 cell.accessoryType = self.pagerView.isInfinite ? .checkmark : .none
+            } else if indexPath.row == 2 {
+                // isItemAdjust
+                cell.accessoryType = self.pagerView.isItemAdjust ? .checkmark : .none
             }
             return cell
         case 1:
@@ -130,6 +133,8 @@ class BasicExampleViewController: UIViewController,UITableViewDataSource,UITable
                 self.pagerView.automaticSlidingInterval = 3.0 - self.pagerView.automaticSlidingInterval
             } else if indexPath.row == 1 { // IsInfinite
                 self.pagerView.isInfinite = !self.pagerView.isInfinite
+            } else if indexPath.row == 2 {
+                self.pagerView.isItemAdjust = !self.pagerView.isItemAdjust
             }
             tableView.reloadSections([indexPath.section], with: .automatic)
         case 1:

Sources/FSPageControl.swift

@@ -103,31 +103,41 @@ open class FSPageControl: UIControl {
 
     open override func layoutSublayers(of layer: CALayer) {
         super.layoutSublayers(of: layer)
-
         let diameter = self.itemSpacing
         let spacing = self.interitemSpacing
+
+        let contentWidth: CGFloat = {
+            var width: CGFloat = 0.0
+            for layer in self.indicatorLayers {
+                width += layer.path?.boundingBoxOfPath.width ?? diameter
+            }
+            width += CGFloat((self.indicatorLayers.count - 1)) * spacing
+            return width
+        }()
+
         var x: CGFloat = {
             switch self.contentHorizontalAlignment {
             case .left, .leading:
                 return 0
             case .center, .fill:
                 let midX = self.contentView.bounds.midX
-                let amplitude = CGFloat(self.numberOfPages/2) * diameter + spacing*CGFloat((self.numberOfPages-1)/2)
-                return midX - amplitude
+                return midX - contentWidth * 0.5
             case .right, .trailing:
-                let contentWidth = diameter*CGFloat(self.numberOfPages) + CGFloat(self.numberOfPages-1)*spacing
                 return contentView.frame.width - contentWidth
             default:
                 return 0
             }
         }()
+
         for (index,value) in self.indicatorLayers.enumerated() {
+            let width = value.path?.boundingBoxOfPath.width ?? diameter
+            let height = value.path?.boundingBoxOfPath.height ?? diameter
             let state: UIControl.State = (index == self.currentPage) ? .selected : .normal
             let image = self.images[state]
-            let size = image?.size ?? CGSize(width: diameter, height: diameter)
-            let origin = CGPoint(x: x - (size.width-diameter)*0.5, y: self.contentView.bounds.midY-size.height*0.5)
+            let size = image?.size ?? CGSize(width: width, height: height)
+            let origin = CGPoint(x: x - (size.width-width)*0.5, y: self.contentView.bounds.midY-size.height*0.5)
             value.frame = CGRect(origin: origin, size: size)
-            x = x + spacing + diameter
+            x = x + spacing + width
         }
 
     }
@@ -221,6 +231,8 @@ open class FSPageControl: UIControl {
         self.setNeedsLayout()
         DispatchQueue.main.async {
             self.updateIndicatorsIfNecessary()
+            // fix：iphone11 pro v17.5.1，更新indicators后没有调用layoutSublayers
+            self.setNeedsLayout()
         }
     }
 

Sources/FSPageViewLayout.swift

@@ -14,6 +14,17 @@ class FSPagerViewLayout: UICollectionViewLayout {
     internal var leadingSpacing: CGFloat = 0
     internal var itemSpacing: CGFloat = 0
     internal var needsReprepare = true
+    internal var isItemAdjust: Bool = true {
+        didSet {
+            guard let collectionView = collectionView else { return }
+            if (isItemAdjust) {
+                self.leadingSpacing = self.scrollDirection == .horizontal ? (collectionView.frame.width-self.actualItemSize.width)*0.5 : (collectionView.frame.height-self.actualItemSize.height)*0.5
+            } else {
+                self.leadingSpacing = 0
+            }
+            self.adjustCollectionViewBounds()
+        }
+    }
     internal var scrollDirection: FSPagerView.ScrollDirection = .horizontal
 
     open override class var layoutAttributesClass: AnyClass {
@@ -75,7 +86,11 @@ class FSPagerViewLayout: UICollectionViewLayout {
             return pagerView.interitemSpacing
         }()
         self.scrollDirection = pagerView.scrollDirection
-        self.leadingSpacing = self.scrollDirection == .horizontal ? (collectionView.frame.width-self.actualItemSize.width)*0.5 : (collectionView.frame.height-self.actualItemSize.height)*0.5
+        if (isItemAdjust) {
+            self.leadingSpacing = self.scrollDirection == .horizontal ? (collectionView.frame.width-self.actualItemSize.width)*0.5 : (collectionView.frame.height-self.actualItemSize.height)*0.5
+        } else {
+            self.leadingSpacing = 0
+        }
         self.itemSpacing = (self.scrollDirection == .horizontal ? self.actualItemSize.width : self.actualItemSize.height) + self.actualInteritemSpacing
 
         // Calculate and cache contentSize, rather than calculating each time
@@ -212,14 +227,14 @@ class FSPagerViewLayout: UICollectionViewLayout {
             if self.scrollDirection == .vertical {
                 return 0
             }
-            let contentOffsetX = origin.x - (collectionView.frame.width*0.5-self.actualItemSize.width*0.5)
+            let contentOffsetX = isItemAdjust ? (origin.x - (collectionView.frame.width*0.5-self.actualItemSize.width*0.5)) : origin.x
             return contentOffsetX
         }()
         let contentOffsetY: CGFloat = {
             if self.scrollDirection == .horizontal {
                 return 0
             }
-            let contentOffsetY = origin.y - (collectionView.frame.height*0.5-self.actualItemSize.height*0.5)
+            let contentOffsetY = isItemAdjust ? (origin.y - (collectionView.frame.height*0.5-self.actualItemSize.height*0.5)) : origin.y
             return contentOffsetY
         }()
         let contentOffset = CGPoint(x: contentOffsetX, y: contentOffsetY)

Sources/FSPagerView.swift

@@ -129,6 +129,15 @@ open class FSPagerView: UIView,UICollectionViewDataSource,UICollectionViewDelega
         }
     }
 
+    // 在banner中显示多项时，true: 调整item位置使其居中显示, false: 不调整
+    @IBInspectable
+    open var isItemAdjust: Bool = true {
+        didSet {
+            self.collectionViewLayout.isItemAdjust = isItemAdjust
+            self.collectionViewLayout.forceInvalidate()
+        }
+    }
+
     /// An unsigned integer value that determines the deceleration distance of the pager view, which indicates the number of passing items during the deceleration. When the value of this property is FSPagerView.automaticDistance, the actual 'distance' is automatically calculated according to the scrolling speed of the pager view. Default is 1.
     @IBInspectable
     open var decelerationDistance: UInt = 1
@@ -252,6 +261,27 @@ open class FSPagerView: UIView,UICollectionViewDataSource,UICollectionViewDelega
         }
         return IndexPath(item: 0, section: 0)
     }
+    // 新增
+    fileprivate var leftmostIndexPath: IndexPath {
+        guard self.numberOfItems > 0, self.collectionView.contentSize != .zero else {
+            return IndexPath(item: 0, section: 0)
+        }
+        let sortedIndexPaths = self.collectionView.indexPathsForVisibleItems.sorted { (l, r) -> Bool in
+            let leftFrame = self.collectionViewLayout.frame(for: l)
+            let rightFrame = self.collectionViewLayout.frame(for: r)
+            switch self.scrollDirection {
+            case .horizontal:
+                return leftFrame.minX < rightFrame.minX
+            case .vertical:
+                return leftFrame.minY < rightFrame.minY
+            }
+        }
+        let indexPath = sortedIndexPaths.first
+        if let indexPath = indexPath {
+            return indexPath
+        }
+        return IndexPath(item: 0, section: 0)
+    }
     fileprivate var isPossiblyRotating: Bool {
         guard let animationKeys = self.contentView.layer.animationKeys() else {
             return false
@@ -278,6 +308,7 @@ open class FSPagerView: UIView,UICollectionViewDataSource,UICollectionViewDelega
         self.backgroundView?.frame = self.bounds
         self.contentView.frame = self.bounds
         self.collectionView.frame = self.contentView.bounds
+        self.collectionViewLayout.needsReprepare = true
     }
 
     open override func willMove(toWindow newWindow: UIWindow?) {
@@ -477,8 +508,15 @@ open class FSPagerView: UIView,UICollectionViewDataSource,UICollectionViewDelega
     /// Reloads all of the data for the collection view.
     @objc(reloadData)
     open func reloadData() {
-        self.collectionViewLayout.needsReprepare = true;
+        self.collectionViewLayout.needsReprepare = true
+        let indexPath = self.collectionView.indexPathsForVisibleItems.first
         self.collectionView.reloadData()
+
+        // fix: 解决在reload时卡在一半的问题
+        if let indexPath = indexPath {
+            let offset = self.collectionViewLayout.contentOffset(for: indexPath)
+            self.collectionView.setContentOffset(offset, animated: false)
+        }
     }
 
     /// Selects the item at the specified index and optionally scrolls it into view.
@@ -561,6 +599,7 @@ open class FSPagerView: UIView,UICollectionViewDataSource,UICollectionViewDelega
 
         // UICollectionView
         let collectionViewLayout = FSPagerViewLayout()
+        collectionViewLayout.isItemAdjust = isItemAdjust
         let collectionView = FSPagerCollectionView(frame: CGRect.zero, collectionViewLayout: collectionViewLayout)
         collectionView.dataSource = self
         collectionView.delegate = self
@@ -585,7 +624,7 @@ open class FSPagerView: UIView,UICollectionViewDataSource,UICollectionViewDelega
             return
         }
         let contentOffset: CGPoint = {
-            let indexPath = self.centermostIndexPath
+            let indexPath = isItemAdjust ? self.centermostIndexPath : self.leftmostIndexPath
             let section = self.numberOfSections > 1 ? (indexPath.section+(indexPath.item+1)/self.numberOfItems) : 0
             let item = (indexPath.item+1) % self.numberOfItems
             return self.collectionViewLayout.contentOffset(for: IndexPath(item: item, section: section))