Update PagerTabStripViewController.swift

Author: Desgard

Sources/PagerTabStripViewController.swift

@@ -147,6 +147,22 @@ open class PagerTabStripViewController: UIViewController, UIScrollViewDelegate {
     open override var shouldAutomaticallyForwardAppearanceMethods: Bool {
         return false
     }
+    
+    // 这里是 default selector pager
+    open func setupDefaultViewController(at index: Int) {
+        guard currentIndex != index else { return }
+        guard isViewLoaded, !self.viewControllers.isEmpty else {
+            currentIndex = index
+            return
+        }
+        guard view.window != nil else {
+        let step = (currentIndex < index) ? 1 : -1
+            for subindex in stride(from: currentIndex+step, through: index, by: step) {
+                containerView.setContentOffset(CGPoint(x: pageOffsetForChild(at: subindex), y: 0), animated: false)
+            }
+            return
+        }
+    }
 
     open func moveToViewController(at index: Int, animated: Bool = true) {
         guard isViewLoaded && view.window != nil && currentIndex != index else {