Merge pull request #99 from kazuhiro4949/feature/add_calculate_underline

add flexible underline and UnderlineFocusView

PagingKit/TitleLabelMenuViewCell.swift

@@ -48,13 +48,22 @@ public class TitleLabelMenuViewCell: PagingMenuViewCell {
         }
     }
 
+    public var labelWidth: CGFloat {
+        return titleLabel.bounds.width
+    }
+
     public let titleLabel = { () -> UILabel in
         let label = UILabel()
         label.font = UIFont.systemFont(ofSize: 17)
         label.textAlignment = .center
         return label
     }()
 
+    public func calcIntermediateLabelSize(with leftCell: TitleLabelMenuViewCell, percent: CGFloat) -> CGFloat {
+        let diff = (labelWidth - leftCell.labelWidth) * percent
+        return leftCell.labelWidth + diff
+    }
+
     public required init?(coder aDecoder: NSCoder) {
         super.init(coder: aDecoder)
         setup()
@@ -71,9 +80,10 @@ public class TitleLabelMenuViewCell: PagingMenuViewCell {
         titleLabel.translatesAutoresizingMaskIntoConstraints = false
         addConstraints([
             anchorLabel(from: titleLabel, to: self, attribute: .top),
-            anchorLabel(from: titleLabel, to: self, attribute: .leading),
-            anchorLabel(from: self, to: titleLabel, attribute: .trailing),
-            anchorLabel(from: self, to: titleLabel, attribute: .bottom)
+            anchorLabel(from: titleLabel, to: self, attribute: .leading, .greaterThanOrEqual),
+            anchorLabel(from: self, to: titleLabel, attribute: .trailing, .greaterThanOrEqual),
+            anchorLabel(from: self, to: titleLabel, attribute: .bottom),
+            anchorLabel(from: titleLabel, to: self, 0, attribute: .centerX)
         ])
     }
 
@@ -89,15 +99,15 @@ public class TitleLabelMenuViewCell: PagingMenuViewCell {
 
 
     /// syntax sugar of NSLayoutConstraint for titleLabel (Because this library supports iOS8, it cannnot use NSLayoutAnchor.)
-    private func anchorLabel(from fromItem: Any, to toItem: Any, attribute: NSLayoutConstraint.Attribute) -> NSLayoutConstraint {
+    private func anchorLabel(from fromItem: Any, to toItem: Any, _ constant: CGFloat = 8, attribute: NSLayoutConstraint.Attribute, _ relatedBy: NSLayoutConstraint.Relation = .equal) -> NSLayoutConstraint {
         return NSLayoutConstraint(
             item: fromItem,
             attribute: attribute,
-            relatedBy: .equal,
+            relatedBy: relatedBy,
             toItem: toItem,
             attribute: attribute,
             multiplier: 1,
-            constant: 8
+            constant: constant
         )
     }
  }

PagingKit/UnderlineFocusView.swift

@@ -43,22 +43,50 @@ public class UnderlineFocusView: UIView {
         }
     }
 
+    public var underlineWidth: CGFloat? = nil {
+        didSet {
+             if let underlineWidth = underlineWidth {
+                 widthConstraint.isActive = true
+                 widthConstraint.constant = underlineWidth
+             } else {
+                 widthConstraint.isActive = false
+             }
+        }
+    }
+
+    private let widthConstraint: NSLayoutConstraint
     private let heightConstraint: NSLayoutConstraint
     private let underlineView = UIView()
 
     required public init?(coder aDecoder: NSCoder) {
+        widthConstraint = NSLayoutConstraint(
+            item: underlineView,
+            attribute: .width,
+            relatedBy: .equal,
+            toItem: nil,
+            attribute: .height, multiplier: 1, constant: 0
+        )
+
         heightConstraint = NSLayoutConstraint(
             item: underlineView,
             attribute: .height,
             relatedBy: .equal,
             toItem: nil,
-            attribute: .height, multiplier: 1, constant: underlineHeight
+            attribute: .height, multiplier: 1, constant: 0
         )
         super.init(coder: aDecoder)
         setup()
     }
 
     override public init(frame: CGRect) {
+        widthConstraint = NSLayoutConstraint(
+            item: underlineView,
+            attribute: .width,
+            relatedBy: .equal,
+            toItem: nil,
+            attribute: .height, multiplier: 1, constant: underlineHeight
+        )
+
         heightConstraint = NSLayoutConstraint(
             item: underlineView,
             attribute: .height,
@@ -74,8 +102,16 @@ public class UnderlineFocusView: UIView {
         addSubview(underlineView)
         underlineView.translatesAutoresizingMaskIntoConstraints = false
         addConstraint(heightConstraint)
-        let constraints = [.bottom, .leading, .trailing].anchor(from: underlineView, to: self)
-        addConstraints(constraints)
+        addConstraint(widthConstraint)
+        widthConstraint.isActive = false
+
+        let constraintsA = [.bottom].anchor(from: underlineView, to: self)
+        let constraintsB = [.width, .centerX].anchor(from: underlineView, to: self)
+        constraintsB.forEach {
+            $0.priority = .defaultHigh
+            $0.isActive = true
+        }
+        addConstraints(constraintsA + constraintsB)
         underlineView.backgroundColor = underlineColor
     }
 }

iOS Sample/iOS Sample/SimpleViewController.swift

@@ -30,6 +30,8 @@ class SimpleViewController: UIViewController {
     var menuViewController: PagingMenuViewController?
     var contentViewController: PagingContentViewController?
 
+    let focusView = UnderlineFocusView()
+
 
     let dataSource: [(menu: String, content: UIViewController)] = ["Martinez", "Alfred", "Louis", "Justin"].map {
         let title = $0
@@ -39,15 +41,17 @@ class SimpleViewController: UIViewController {
 
     lazy var firstLoad: (() -> Void)? = { [weak self, menuViewController, contentViewController] in
         menuViewController?.reloadData()
-        contentViewController?.reloadData()
+        contentViewController?.reloadData { [weak self] in
+            self?.adjustfocusViewWidth(index: 0, percent: 0)
+        }
         self?.firstLoad = nil
     }
 
     override func viewDidLoad() {
         super.viewDidLoad()
 
         menuViewController?.register(type: TitleLabelMenuViewCell.self, forCellWithReuseIdentifier: "identifier")
-        menuViewController?.registerFocusView(view: UnderlineFocusView())
+        menuViewController?.registerFocusView(view: focusView)
         contentViewController?.scrollView.bounces = true
     }
     override func viewDidLayoutSubviews() {
@@ -115,6 +119,15 @@ extension SimpleViewController: PagingMenuViewControllerDelegate {
 extension SimpleViewController: PagingContentViewControllerDelegate {
     func contentViewController(viewController: PagingContentViewController, didManualScrollOn index: Int, percent: CGFloat) {
         menuViewController?.scroll(index: index, percent: percent, animated: false)
+        adjustfocusViewWidth(index: index, percent: percent)
+    }
+
+    func adjustfocusViewWidth(index: Int, percent: CGFloat) {
+        guard let leftCell = menuViewController?.cellForItem(at: index) as? TitleLabelMenuViewCell,
+            let rightCell = menuViewController?.cellForItem(at: index + 1) as? TitleLabelMenuViewCell else {
+            return
+        }
+        focusView.underlineWidth = rightCell.calcIntermediateLabelSize(with: leftCell, percent: percent)
     }
 }