Merge pull request #80 from Yalantis/feature/always_visible_PullToRefresh

Added "shouldBeVisibleWhileScrolling" property to PullToRefresh

Author: Sergey D

PullToRefresh/PullToRefresh.swift

@@ -22,7 +22,14 @@ open class PullToRefresh: NSObject {
     open var springDamping: CGFloat = 0.4
     open var initialSpringVelocity: CGFloat = 0.8
     open var animationOptions: UIViewAnimationOptions = [.curveLinear]
-
+    open var shouldBeVisibleWhileScrolling: Bool = false {
+        willSet{
+            if shouldBeVisibleWhileScrolling {
+                sendRefreshViewToScrollView()
+            }
+        }
+    }
+    
     let refreshView: UIView
     var action: (() -> ())?
 
@@ -58,6 +65,15 @@ open class PullToRefresh: NSObject {
     // MARK: - State
 
     open fileprivate(set) var state: State = .initial {
+        willSet{
+            switch newValue {
+            case .finished:
+                if shouldBeVisibleWhileScrolling {
+                    sendRefreshViewToScrollView()
+                }
+            default: break
+            }
+        }
         didSet {
             animator.animate(state)
             switch state {
@@ -243,6 +259,9 @@ private extension PullToRefresh {
             },
             completion: { _ in
                 scrollView.bounces = true
+                if self.shouldBeVisibleWhileScrolling {
+                    self.bringRefreshViewToSuperview()
+                }
             }
         )
 
@@ -287,4 +306,22 @@ private extension PullToRefresh {
 
         return scrollView.contentOffset.y <= -defaultInsets.top
     }
+    
+    func bringRefreshViewToSuperview() {
+        guard let scrollView = scrollView, let superView = scrollView.superview else { return }
+        guard let scrollViewIndex = superView.subviews.index(of: scrollView) else { return }
+        let frame = scrollView.convert(refreshView.frame, to: superView)
+        refreshView.removeFromSuperview()
+        superView.insertSubview(refreshView, at: scrollViewIndex + 1)
+        refreshView.frame = frame
+    }
+    
+    func sendRefreshViewToScrollView() {
+        refreshView.removeFromSuperview()
+        guard let scrollView = scrollView else { return }
+        scrollView.addSubview(refreshView)
+        refreshView.frame = scrollView.defaultFrame(forPullToRefresh: self)
+        scrollView.sendSubview(toBack: refreshView)
+    }
+    
 }

PullToRefresh/UIScrollView+PullToRefresh.swift

@@ -33,28 +33,35 @@ public extension UIScrollView {
         }
     }
 
+    internal func defaultFrame(forPullToRefresh pullToRefresh: PullToRefresh) -> CGRect {
+        let view = pullToRefresh.refreshView
+        var originY: CGFloat
+        switch pullToRefresh.position {
+        case .top:
+            originY = -view.frame.size.height
+        case .bottom:
+            originY = contentSize.height
+        }
+        return CGRect(x: 0, y: originY, width: frame.width, height: view.frame.height)
+    }
+    
     public func addPullToRefresh(_ pullToRefresh: PullToRefresh, action: @escaping () -> ()) {
         pullToRefresh.scrollView = self
         pullToRefresh.action = action
 
-        var originY: CGFloat
         let view = pullToRefresh.refreshView
 
         switch pullToRefresh.position {
         case .top:
             removePullToRefresh(at: .top)
-            
             topPullToRefresh = pullToRefresh
-            originY = -view.frame.size.height
 
         case .bottom:
             removePullToRefresh(at: .bottom)
-            
             bottomPullToRefresh = pullToRefresh
-            originY = contentSize.height
         }
 
-        view.frame = CGRect(x: 0, y: originY, width: frame.width, height: view.frame.height)
+        view.frame = defaultFrame(forPullToRefresh: pullToRefresh)
 
         addSubview(view)
         sendSubview(toBack: view)