From 1bda17f09a422ce6e97b3904b2b0e806f7611d68 Mon Sep 17 00:00:00 2001
From: pera <pera@xmartlabs.com>
Date: Thu, 4 May 2017 17:16:35 -0300
Subject: [PATCH] Fixes #357

---
 Sources/ButtonBarPagerTabStripViewController.swift |  2 +-
 Sources/PagerTabStripViewController.swift          | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Sources/ButtonBarPagerTabStripViewController.swift b/Sources/ButtonBarPagerTabStripViewController.swift
index d4e1c1c..790c7ee 100644
--- a/Sources/ButtonBarPagerTabStripViewController.swift
+++ b/Sources/ButtonBarPagerTabStripViewController.swift
@@ -266,7 +266,7 @@ open class ButtonBarPagerTabStripViewController: PagerTabStripViewController, Pa
         return cells
     }
 
-    // MARK: - UICollectionViewDelegateFlowLayut
+    // MARK: - UICollectionViewDelegateFlowLayout
     
     open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: IndexPath) -> CGSize {
         guard let cellWidthValue = cachedCellWidths?[indexPath.row] else {
diff --git a/Sources/PagerTabStripViewController.swift b/Sources/PagerTabStripViewController.swift
index 564124e..672db6e 100644
--- a/Sources/PagerTabStripViewController.swift
+++ b/Sources/PagerTabStripViewController.swift
@@ -62,6 +62,7 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
     
     open private(set) var viewControllers = [UIViewController]()
     open private(set) var currentIndex = 0
+    open private(set) var preCurrentIndex = 0 // used *only* to store the index to which move when the pager becomes visible
     
     open var pageWidth: CGFloat {
         return containerView.bounds.width
@@ -123,6 +124,10 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
         super.viewDidAppear(animated)
         lastSize = containerView.bounds.size
         updateIfNeeded()
+        let needToUpdateCurrentChild = preCurrentIndex != currentIndex
+        if needToUpdateCurrentChild {
+            moveToViewController(at: preCurrentIndex)
+        }
         isViewAppearing = false
         childViewControllers.forEach { $0.endAppearanceTransition() }
     }
@@ -148,9 +153,10 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
     
     open func moveToViewController(at index: Int, animated: Bool = true) {
         guard isViewLoaded && view.window != nil && currentIndex != index else {
-            currentIndex = index
+            preCurrentIndex = index
             return
         }
+        
         if animated && pagerBehaviour.skipIntermediateViewControllers && abs(currentIndex - index) > 1 {
             var tmpViewControllers = viewControllers
             let currentChildVC = viewControllers[currentIndex]
@@ -268,6 +274,7 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
         let virtualPage = virtualPageFor(contentOffset: containerView.contentOffset.x)
         let newCurrentIndex = pageFor(virtualPage: virtualPage)
         currentIndex = newCurrentIndex
+        preCurrentIndex = currentIndex
         let changeCurrentIndex = newCurrentIndex != oldCurrentIndex
         
         if let progressiveDeledate = self as? PagerTabStripIsProgressiveDelegate, pagerBehaviour.isProgressiveIndicator {
@@ -296,6 +303,7 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
         if currentIndex >= viewControllers.count {
             currentIndex = viewControllers.count - 1
         }
+        preCurrentIndex = currentIndex
         containerView.contentOffset = CGPoint(x: pageOffsetForChild(at: currentIndex), y: 0)
         updateContent()
     }
@@ -333,6 +341,7 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
             guard let me = self else { return }
             me.isViewRotating = false
             me.currentIndex = me.pageBeforeRotate
+            me.preCurrentIndex = me.currentIndex
             me.updateIfNeeded()
         }
     }