diff --git a/DropdownMenu/DropUpMenu.swift b/DropdownMenu/DropUpMenu.swift
index 6daf213..db3d4b3 100644
--- a/DropdownMenu/DropUpMenu.swift
+++ b/DropdownMenu/DropUpMenu.swift
@@ -20,7 +20,8 @@ public protocol DropUpMenuDelegate: class {
     func dropUpMenu(_ dropUpMenu: DropUpMenu, cellForRowAt indexPath: IndexPath) -> UITableViewCell?
     func dropUpMenu(_ dropUpMenu: DropUpMenu, didSelectRowAt indexPath: IndexPath)
     func dropUpMenuCancel(_ dropUpMenu: DropUpMenu)
-    func dropUpMenuWillDismiss(_ dropUpMenu: DropdownMenu)
+    func dropUpMenuWillDismiss(_ dropUpMenu: DropUpMenu)
+    func dropUpMenuWillShow(_ dropUpMenu: DropUpMenu)
 }
 
 public extension DropUpMenuDelegate {
@@ -28,14 +29,13 @@ public extension DropUpMenuDelegate {
         return nil
     }
     
-    func dropUpMenu(_ dropUpMenu: DropUpMenu, didSelectRowAt indexPath: IndexPath) {
-    }
+    func dropUpMenu(_ dropUpMenu: DropUpMenu, didSelectRowAt indexPath: IndexPath) { }
     
-    func dropUpMenuCancel(_ dropUpMenu: DropUpMenu) {
-    }
+    func dropUpMenuCancel(_ dropUpMenu: DropUpMenu) { }
   
-    func dropUpMenuWillDismiss(_ dropUpMenu: DropUpMenu) {
-    }
+    func dropUpMenuWillDismiss(_ dropUpMenu: DropUpMenu) { }
+  
+    func dropUpMenuWillShow(_ dropUpMenu: DropUpMenu) { }
 }
 
 private let screenRect = UIScreen.main.bounds
@@ -152,6 +152,7 @@ open class DropUpMenu: UIView {
     }
     
     open func showMenu() {
+        delegate?.dropUpMenuWillShow(self)
         if isShow {
             hideMenu()
             return
diff --git a/DropdownMenu/DropdownMenu.swift b/DropdownMenu/DropdownMenu.swift
index c3818d7..c0b1299 100644
--- a/DropdownMenu/DropdownMenu.swift
+++ b/DropdownMenu/DropdownMenu.swift
@@ -13,6 +13,7 @@ public protocol DropdownMenuDelegate: class {
     func dropdownMenu(_ dropdownMenu: DropdownMenu, didSelectRowAt indexPath: IndexPath)
     func dropdownMenuCancel(_ dropdownMenu: DropdownMenu)
     func dropdownMenuWillDismiss(_ dropdownMenu: DropdownMenu)
+    func dropdownMenuWillShow(_ dropdownMenu: DropdownMenu)
 }
 
 public extension DropdownMenuDelegate {
@@ -20,6 +21,7 @@ public extension DropdownMenuDelegate {
     func dropdownMenu(_ dropdownMenu: DropdownMenu, didSelectRowAt indexPath: IndexPath) { }
     func dropdownMenuCancel(_ dropdownMenu: DropdownMenu) { }
     func dropdownMenuWillDismiss(_ dropdownMenu: DropdownMenu) { }
+    func dropdownMenuWillShow(_ dropdownMenu: DropdownMenu) { }
 }
 
 open class DropdownMenu: UIView {
@@ -36,7 +38,11 @@ open class DropdownMenu: UIView {
     fileprivate let portraitTopOffset: CGFloat = 64.0
     fileprivate let landscapeTopOffset: CGFloat = 32.0
     fileprivate var topLayoutConstraintConstant: CGFloat {
-        return navigationController.navigationBar.frame.height + navigationController.navigationBar.frame.origin.y + topOffsetY
+        var offset: CGFloat = 0
+        if !navigationController.isNavigationBarHidden {
+          offset = navigationController.navigationBar.frame.height + navigationController.navigationBar.frame.origin.y
+        }
+        return offset + topOffsetY
     }
     
     open weak var delegate: DropdownMenuDelegate?
@@ -197,6 +203,7 @@ open class DropdownMenu: UIView {
     }
     
     open func showMenu(isOnNavigaitionView: Bool = false) {
+        delegate?.dropdownMenuWillShow(self)
         if isShow {
             hideMenu()
             return
diff --git a/TBDropdownMenu.podspec b/TBDropdownMenu.podspec
index 404075c..cb58d69 100644
--- a/TBDropdownMenu.podspec
+++ b/TBDropdownMenu.podspec
@@ -16,7 +16,7 @@ Pod::Spec.new do |s|
   #
 
   s.name         = "TBDropdownMenu"
-  s.version      = "2.3.0"
+  s.version      = "2.4.1"
   s.summary      = "TBDropdownMenu is a dropdown menu for navigationController in Swift"
 
   # This description is used to generate tags and improve search results.