fix Match transition inside a nav controller

Author: lkzhao

Sources/Hero2/Base/Transition.swift

@@ -48,6 +48,7 @@ open class Transition: NSObject {
     private var canAddBlocks: Bool = false
     private var dismissBlocks: [() -> Void] = []
     private var presentBlocks: [() -> Void] = []
+    private var startBlocks: [() -> Void] = []
     private var completeBlocks: [(Bool) -> Void] = []
     private var prepareBlocks: [() -> Void] = []
     private var pausedAnimations: [UIView: [String: CAAnimation]] = [:]
@@ -122,6 +123,10 @@ open class Transition: NSObject {
         prepareBlocks.append(block)
     }
 
+    public func addStartBlock(_ block: @escaping () -> Void) {
+        startBlocks.append(block)
+    }
+
     // MARK: - Subclass Overrides
     open func animate() {}
 }
@@ -277,6 +282,12 @@ extension Transition: UIViewControllerAnimatedTransitioning {
                 }
 
             animator.startAnimation()
+
+            for block in startBlocks {
+                block()
+            }
+            startBlocks = []
+
             if isInteractive {
                 animator.pauseAnimation()
             }

Sources/Hero2/BuiltinTransitions/MatchModalTransition.swift

@@ -110,15 +110,17 @@ open class MatchModalTransition: Transition {
             sourceViewPlaceholder.removeFromSuperview()
             foregroundContainerView.removeFromSuperview()
         }
+        addStartBlock {
+            if self.isInteractive, self.isMatched {
+                self.pauseForegroundView()
+            }
+        }
     }
 
-    open override func animateTransition(using context: UIViewControllerContextTransitioning) {
-        super.animateTransition(using: context)
-        if isInteractive, isMatched {
-            let position = foregroundContainerView.layer.presentation()?.position ?? foregroundContainerView.layer.position
-            pause(view: foregroundContainerView, animationForKey: "position")
-            foregroundContainerView.layer.position = position
-        }
+    func pauseForegroundView() {
+        let position = foregroundContainerView.layer.presentation()?.position ?? foregroundContainerView.layer.position
+        self.pause(view: foregroundContainerView, animationForKey: "position")
+        foregroundContainerView.layer.position = position
     }
 
     open override func animationEnded(_ transitionCompleted: Bool) {