Improve context menus on old versions of Android

* java/org/gnu/emacs/EmacsActivity.java (EmacsActivity): New
field `lastClosedMenu'.
(onContextMenuClosed): Don't send event if a menu is closed
twice in a row.  Also, clear wasSubmenuSelected immediately.
* java/org/gnu/emacs/EmacsContextMenu.java: Display submenus
manually in Android 6.0 and earlier.
* java/org/gnu/emacs/EmacsView.java (onCreateContextMenu)
(popupMenu): Adjust accordingly.

3 files changed, 76 insertions, 31 deletions

diff --git a/java/org/gnu/emacs/EmacsActivity.java b/java/org/gnu/emacs/EmacsActivity.java
index 62bef33fab3..13002d5d0e5 100644
--- a/java/org/gnu/emacs/EmacsActivity.java
+++ b/java/org/gnu/emacs/EmacsActivity.java
@@ -65,6 +65,9 @@ public class EmacsActivity extends Activity
   /* Whether or not this activity is fullscreen.  */
   private boolean isFullscreen;
 
+  /* The last context menu to be closed.  */
+  private Menu lastClosedMenu;
+
   static
   {
     focusedActivities = new ArrayList<EmacsActivity> ();
@@ -308,9 +311,19 @@ public class EmacsActivity extends Activity
     Log.d (TAG, "onContextMenuClosed: " + menu);
 
     /* See the comment inside onMenuItemClick.  */
+
     if (EmacsContextMenu.wasSubmenuSelected
-        && menu.toString ().contains ("ContextMenuBuilder"))
-      return;
+        || menu == lastClosedMenu)
+      {
+        EmacsContextMenu.wasSubmenuSelected = false;
+        lastClosedMenu = menu;
+        return;
+      }
+
+    /* lastClosedMenu is set because Android apparently calls this
+       function twice.  */
+
+    lastClosedMenu = null;
 
     /* Send a context menu event given that no menu item has already
        been selected.  */
diff --git a/java/org/gnu/emacs/EmacsContextMenu.java b/java/org/gnu/emacs/EmacsContextMenu.java
index a1bca98daa0..d1a624e68d9 100644
--- a/java/org/gnu/emacs/EmacsContextMenu.java
+++ b/java/org/gnu/emacs/EmacsContextMenu.java
@@ -58,6 +58,7 @@ public final class EmacsContextMenu
     public String itemName, tooltip;
     public EmacsContextMenu subMenu;
     public boolean isEnabled, isCheckable, isChecked;
+    public EmacsView inflatedView;
 
     @Override
     public boolean
@@ -67,6 +68,34 @@ public final class EmacsContextMenu
 
       if (subMenu != null)
         {
+          /* Android 6.0 and earlier don't support nested submenus
+             properly, so display the submenu popup by hand.  */
+
+          if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N)
+            {
+              Log.d (TAG, "onMenuItemClick: displaying submenu " + subMenu);
+
+              /* Still set wasSubmenuSelected -- if not set, the
+                 dismissal of this context menu will result in a
+                 context menu event being sent.  */
+              wasSubmenuSelected = true;
+
+              /* Running a popup menu from inside a click handler
+                 doesn't work, so make sure it is displayed
+                 outside.  */
+
+              inflatedView.post (new Runnable () {
+                  @Override
+                  public void
+                  run ()
+                  {
+                    inflatedView.popupMenu (subMenu, 0, 0, true);
+                  }
+                });
+
+              return true;
+            }
+
           /* After opening a submenu within a submenu, Android will
              send onContextMenuClosed for a ContextMenuBuilder.  This
              will normally confuse Emacs into thinking that the
@@ -164,10 +193,11 @@ public final class EmacsContextMenu
     return item.subMenu;
   }
 
-  /* Add the contents of this menu to MENU.  */
+  /* Add the contents of this menu to MENU.  Assume MENU will be
+     displayed in INFLATEDVIEW.  */
 
   private void
-  inflateMenuItems (Menu menu)
+  inflateMenuItems (Menu menu, EmacsView inflatedView)
   {
     Intent intent;
     MenuItem menuItem;
@@ -177,26 +207,26 @@ public final class EmacsContextMenu
       {
         if (item.subMenu != null)
           {
-            try
+            /* This is a submenu.  On versions of Android which
+               support doing so, create the submenu and add the
+               contents of the menu to it.
+
+               Note that Android 4.0 and later technically supports
+               having multiple layers of nested submenus, but if they
+               are used, onContextMenuClosed becomes unreliable.  */
+
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N)
               {
-                /* This is a submenu.  On versions of Android which
-                   support doing so, create the submenu and add the
-                   contents of the menu to it.  */
                 submenu = menu.addSubMenu (item.itemName);
-                item.subMenu.inflateMenuItems (submenu);
-              }
-            catch (UnsupportedOperationException exception)
-              {
-                /* This version of Android has a restriction
-                   preventing submenus from being added to submenus.
-                   Inflate everything into the parent menu
-                   instead.  */
-                item.subMenu.inflateMenuItems (menu);
-                continue;
+                item.subMenu.inflateMenuItems (submenu, inflatedView);
+
+                /* This is still needed to set wasSubmenuSelected.  */
+                menuItem = submenu.getItem ();
               }
+            else
+              menuItem = menu.add (item.itemName);
 
-            /* This is still needed to set wasSubmenuSelected.  */
-            menuItem = submenu.getItem ();
+            item.inflatedView = inflatedView;
             menuItem.setOnMenuItemClickListener (item);
           }
         else
@@ -227,16 +257,14 @@ public final class EmacsContextMenu
       }
   }
 
-  /* Enter the items in this context menu to MENU.  Create each menu
-     item with an Intent containing a Bundle, where the key
-     "emacs:menu_item_hi" maps to the high 16 bits of the
-     corresponding item ID, and the key "emacs:menu_item_low" maps to
-     the low 16 bits of the item ID.  */
+  /* Enter the items in this context menu to MENU.
+     Assume that MENU will be displayed in VIEW; this may lead to
+     popupMenu being called on VIEW if a submenu is selected.  */
 
   public void
-  expandTo (Menu menu)
+  expandTo (Menu menu, EmacsView view)
   {
-    inflateMenuItems (menu);
+    inflateMenuItems (menu, view);
   }
 
   /* Return the parent or NULL.  */
@@ -260,7 +288,8 @@ public final class EmacsContextMenu
     /* No submenu has been selected yet.  */
     wasSubmenuSelected = false;
 
-    return window.view.popupMenu (this, xPosition, yPosition);
+    return window.view.popupMenu (this, xPosition, yPosition,
+                                  false);
   }
 
   /* Display this context menu on WINDOW, at xPosition and
diff --git a/java/org/gnu/emacs/EmacsView.java b/java/org/gnu/emacs/EmacsView.java
index d2330494bc7..617836d8811 100644
--- a/java/org/gnu/emacs/EmacsView.java
+++ b/java/org/gnu/emacs/EmacsView.java
@@ -464,19 +464,22 @@ public final class EmacsView extends ViewGroup
     if (contextMenu == null)
       return;
 
-    contextMenu.expandTo (menu);
+    contextMenu.expandTo (menu, this);
   }
 
   public boolean
   popupMenu (EmacsContextMenu menu, int xPosition,
-             int yPosition)
+             int yPosition, boolean force)
   {
-    if (popupActive)
+    if (popupActive && !force)
       return false;
 
     contextMenu = menu;
     popupActive = true;
 
+    Log.d (TAG, "popupMenu: " + menu + " @" + xPosition
+           + ", " + yPosition + " " + force);
+
     /* Use showContextMenu (float, float) on N to get actual popup
        behavior.  */
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N)