Support tab bar height

Sources/KeyboardLayoutGuide/KeyboardLayoutGuide.swift

@@ -1,3 +1,4 @@
+
 //
 //  Keyboard+LayoutGuide.swift
 //  KeyboardLayoutGuide
@@ -18,19 +19,19 @@ extension UIView {
         static var usingSafeArea = "KeyboardLayoutGuideUsingSafeArea"
         static var notUsingSafeArea = "KeyboardLayoutGuide"
     }
-
+    
     /// A layout guide representing the inset for the keyboard.
     /// Use this layout guide’s top anchor to create constraints pinning to the top of the keyboard or the bottom of safe area.
     public var keyboardLayoutGuide: UILayoutGuide {
         getOrCreateKeyboardLayoutGuide(identifier: Identifiers.usingSafeArea, usesSafeArea: true)
     }
-
+    
     /// A layout guide representing the inset for the keyboard.
     /// Use this layout guide’s top anchor to create constraints pinning to the top of the keyboard or the bottom of the view.
     public var keyboardLayoutGuideNoSafeArea: UILayoutGuide {
         getOrCreateKeyboardLayoutGuide(identifier: Identifiers.notUsingSafeArea, usesSafeArea: false)
     }
-
+    
     private func getOrCreateKeyboardLayoutGuide(identifier: String, usesSafeArea: Bool) -> UILayoutGuide {
         if let existing = layoutGuides.first(where: { $0.identifier == identifier }) {
             return existing
@@ -50,14 +51,14 @@ open class KeyboardLayoutGuide: UILayoutGuide {
             updateButtomAnchor()
         }
     }
-
+    
     private var bottomConstraint: NSLayoutConstraint?
-
+    
     @available(*, unavailable)
     public required init?(coder aDecoder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
-
+    
     public init(notificationCenter: NotificationCenter = NotificationCenter.default) {
         super.init()
         // Observe keyboardWillChangeFrame notifications
@@ -68,7 +69,7 @@ open class KeyboardLayoutGuide: UILayoutGuide {
             object: nil
         )
     }
-
+    
     internal func setUp() {
         guard let view = owningView else { return }
         NSLayoutConstraint.activate(
@@ -80,39 +81,51 @@ open class KeyboardLayoutGuide: UILayoutGuide {
         )
         updateButtomAnchor()
     }
-
+    
     func updateButtomAnchor() {
         if let bottomConstraint = bottomConstraint {
             bottomConstraint.isActive = false
         }
-
+        
         guard let view = owningView else { return }
-
+        
         let viewBottomAnchor: NSLayoutYAxisAnchor
         if #available(iOS 11.0, *), usesSafeArea {
             viewBottomAnchor = view.safeAreaLayoutGuide.bottomAnchor
         } else {
             viewBottomAnchor = view.bottomAnchor
         }
-
+        
         bottomConstraint = bottomAnchor.constraint(equalTo: viewBottomAnchor)
         bottomConstraint?.isActive = true
     }
-
+    
     @objc
     private func keyboardWillChangeFrame(_ note: Notification) {
         if var height = note.keyboardHeight, let duration = note.animationDuration {
+
+            let presentedView = UIApplication.topViewController()
+
+            var tabBarHeight: CGFloat = 0
+
+            if presentedView?.tabBarController?.tabBar.isHidden == false {
+                tabBarHeight = presentedView?.tabBarController?.tabBar.frame.height ?? 0
+            }
+
             if #available(iOS 11.0, *), usesSafeArea, height > 0, let bottom = owningView?.safeAreaInsets.bottom {
-                height -= bottom
+                height -= bottom + tabBarHeight
             }
+
             heightConstraint?.constant = height
+
             if duration > 0.0 {
                 animate(note)
             }
+
             Keyboard.shared.currentHeight = height
         }
     }
-
+    
     private func animate(_ note: Notification) {
         if
             let owningView = self.owningView,
@@ -153,6 +166,23 @@ extension Notification {
     }
 }
 
+extension UIApplication {
+    class func topViewController(base: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
+
+        if let nav = base as? UINavigationController {
+            return topViewController(base: nav.visibleViewController)
+        } else if let tab = base as? UITabBarController {
+            if let selected = tab.selectedViewController {
+                return topViewController(base: selected)
+            }
+        } else if let presented = base?.presentedViewController {
+            return topViewController(base: presented)
+        }
+
+        return base
+    }
+}
+
 // Credits to John Gibb for this nice helper :)
 // https://stackoverflow.com/questions/1536923/determine-if-uiview-is-visible-to-the-user
 func isVisible(view: UIView) -> Bool {