[ContextMenu] Improvements to Android icon and auto-close when app goes to background (#324)

* made sure android does not crash if you add a icon to a context menu item

* made sure we close the context menu when the app goes from background to foreground

* made sure we close the context menu when the app goes to background on ios

Author: haavamoa

src/DIPS.Xamarin.UI.Android/ContextMenu/ContextMenuButtonRenderer.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Android.App;
 using Android.Content;
+using Android.OS;
 using Android.Support.V7.View.Menu;
 using Android.Views;
 using AndroidX.AppCompat.Widget;
@@ -11,16 +13,18 @@
 using Xamarin.Forms;
 using Xamarin.Forms.Internals;
 using Xamarin.Forms.Platform.Android;
+using Application = Android.App.Application;
 
 [assembly: ExportRenderer(typeof(ContextMenuButton), typeof(ContextMenuButtonRenderer))]
 
 namespace DIPS.Xamarin.UI.Android.ContextMenu
 {
-    internal class ContextMenuButtonRenderer : ButtonRenderer, PopupMenu.IOnMenuItemClickListener
+    internal class ContextMenuButtonRenderer : ButtonRenderer, PopupMenu.IOnMenuItemClickListener, Application.IActivityLifecycleCallbacks
     {
         private readonly Context m_context;
         private ContextMenuButton m_contextMenuButton;
         private Dictionary<ContextMenuItem, IMenuItem> m_menuItems;
+        private MenuPopupHelper? m_menuHelper; //Might be null if the user never tapped the button to open it
 
         public ContextMenuButtonRenderer(Context context) : base(context)
         {
@@ -40,11 +44,13 @@ protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
                 {
                     {
                         contextMenuButton.Clicked += OpenContextMenu;
+                        (((Activity)Context!)).RegisterActivityLifecycleCallbacks(this);
                     }
                 }
                 else
                 {
                     contextMenuButton.Clicked -= OpenContextMenu;
+                    (((Activity)Context!)).UnregisterActivityLifecycleCallbacks(this);
                 }
             }
         }
@@ -58,10 +64,10 @@ private void OpenContextMenu(object sender, EventArgs e)
                 m_menuItems = ContextMenuHelper.CreateMenuItems(m_context, m_contextMenuButton.ItemsSource,
                 m_contextMenuButton, popupMenu);
             popupMenu.SetOnMenuItemClickListener(this);
-            var menuHelper = new MenuPopupHelper(Context,(MenuBuilder) popupMenu.Menu, Control);
-            menuHelper.Gravity = gravity;
-            menuHelper.SetForceShowIcon(m_menuItems.Keys.Any(contextMenuItem => !string.IsNullOrEmpty(contextMenuItem.Icon) || !string.IsNullOrEmpty(contextMenuItem.AndroidOptions.IconResourceName))); //Show icons if there is any context menu items with a icon added
-            menuHelper.Show();
+            m_menuHelper = new MenuPopupHelper(Context,(MenuBuilder) popupMenu.Menu, Control);
+            m_menuHelper.Gravity = gravity;
+            m_menuHelper.SetForceShowIcon(m_menuItems.Keys.Any(contextMenuItem => !string.IsNullOrEmpty(contextMenuItem.Icon) || !string.IsNullOrEmpty(contextMenuItem.AndroidOptions.IconResourceName))); //Show icons if there is any context menu items with a icon added
+            m_menuHelper.Show();
             m_contextMenuButton.SendContextMenuOpened();
         }
 
@@ -98,5 +104,38 @@ public bool OnMenuItemClick(IMenuItem theTappedNativeItem)
 
             return false;
         }
+
+        public void OnActivityCreated(Activity activity, Bundle savedInstanceState)
+        {
+            
+        }
+
+        public void OnActivityDestroyed(Activity activity)
+        {
+        }
+
+        public void OnActivityPaused(Activity activity)
+        {
+            if (m_menuHelper is {IsShowing: true})
+            {
+                m_menuHelper.Dismiss();    
+            }
+        }
+
+        public void OnActivityResumed(Activity activity)
+        {
+        }
+
+        public void OnActivitySaveInstanceState(Activity activity, Bundle outState)
+        {
+        }
+
+        public void OnActivityStarted(Activity activity)
+        {
+        }
+
+        public void OnActivityStopped(Activity activity)
+        {
+        }
     }
 }

src/DIPS.Xamarin.UI.Android/ContextMenu/ContextMenuHelper.cs

@@ -92,8 +92,14 @@ private static void UpdateMenuItem(Context context, ContextMenuButton contextMen
             if (!string.IsNullOrEmpty(contextMenuItem.Icon))
             {
                 var id = context.Resources?.GetIdentifier(contextMenuItem.Icon, "drawable", context.PackageName);
-                var androidResourceId = context.Resources?.GetIdentifier(contextMenuItem.AndroidOptions.IconResourceName, "drawable",context.PackageName);
-                id = androidResourceId ?? id;
+                if (!string.IsNullOrEmpty(contextMenuItem.AndroidOptions.IconResourceName))
+                {
+                    var androidResourceId= context.Resources?.GetIdentifier(contextMenuItem.AndroidOptions.IconResourceName, "drawable",context.PackageName);
+                    if (androidResourceId != null)
+                    {
+                        id = androidResourceId;
+                    }
+                }
                 if (id != null)
                 {
                     menuItem.SetIcon((int)id);   

src/DIPS.Xamarin.UI.iOS/ContextMenu/ContextMenuButtonRenderer.cs

@@ -5,6 +5,7 @@
 using CoreGraphics;
 using DIPS.Xamarin.UI.Controls.ContextMenu;
 using DIPS.Xamarin.UI.iOS.ContextMenu;
+using Foundation;
 using ObjCRuntime;
 using UIKit;
 using Xamarin.Forms;
@@ -35,6 +36,11 @@ protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
                             CreateMenu(); //Create the menu the first time so it shows up the first time the user taps the button
                         Control.TouchDown += OnTouchDown;
                         Control.ShowsMenuAsPrimaryAction = true;
+                        NSNotificationCenter.DefaultCenter.AddObserver(UIApplication.DidEnterBackgroundNotification, notification =>
+                        {
+                            Control.Menu = null;
+                            Control.Menu = CreateMenu(); //Recreate the menu to close it, and to make it possible to re-open it in one tap after it went to the background
+                        });
                     }
                 }
             }
@@ -43,6 +49,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
                 if (Control != null)
                 {
                     Control.TouchDown -= OnTouchDown;
+                    NSNotificationCenter.DefaultCenter.RemoveObserver(UIApplication.DidEnterBackgroundNotification);
                 }
             }
         }