fix navbar shadow

@@ -52,13 +52,6 @@ extension UIViewController {
         navigationItem.standardAppearance = navigationBarAppearance
         navigationItem.compactAppearance = navigationBarAppearance
         navigationItem.scrollEdgeAppearance = navigationBarAppearance
-        
-        // Add shadow
-        self.navigationController?.navigationBar.layer.masksToBounds = false
-        self.navigationController?.navigationBar.layer.shadowColor = UIColor.lightGray.cgColor
-        self.navigationController?.navigationBar.layer.shadowOpacity = 0.8
-        self.navigationController?.navigationBar.layer.shadowOffset = CGSize(width: 0, height: 2.0)
-        self.navigationController?.navigationBar.layer.shadowRadius = 2
     }
     
     
@@ -66,6 +59,15 @@ extension UIViewController {
         self.navigationController?.popViewController(animated: true)
         self.dismiss(animated: true, completion: {})
     }
+
+    func addNavShadow() {
+        // Add shadow
+        self.navigationController?.navigationBar.layer.masksToBounds = false
+        self.navigationController?.navigationBar.layer.shadowColor = UIColor.lightGray.cgColor
+        self.navigationController?.navigationBar.layer.shadowOpacity = 0.8
+        self.navigationController?.navigationBar.layer.shadowOffset = CGSize(width: 0, height: 2.0)
+        self.navigationController?.navigationBar.layer.shadowRadius = 2
+    }
     
     func setNavigationTitle(_ title: String, _ fontWeight: String? = "medium") {
         let uiscreen: CGRect = UIScreen.main.bounds

@@ -291,6 +291,8 @@ import SwiftEventBus
 
     public override func viewWillAppear(_ animated: Bool) {
         super.viewWillAppear(animated)
+
+        addNavShadow()
         
         let userTag = swiftApi().getUserTag()
         if (questionnaireButton.currentTitle != userTag) {
@@ -327,6 +329,15 @@ import SwiftEventBus
 
         self.coupons = swiftApi().getCouponList()
         self.tableView.reloadData()
+
+        self.startTimer()
+    }
+
+    public override func viewWillDisappear(_ animated: Bool) {
+        super.viewWillDisappear(animated)
+
+        self.stopTimer()
+        self.navigationController?.navigationBar.layer.shadowOpacity = 0.0
     }
 
     public override func viewDidLayoutSubviews() {