core/java/com/android/internal/view/menu/MenuBuilder.java

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.internal.view.menu;


import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.graphics.drawable.Drawable;
import android.os.Parcelable;
import android.util.Log;
import android.util.SparseArray;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.KeyCharacterMap;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.SubMenu;
import android.view.View;

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * Implementation of the {@link android.view.Menu} interface for creating a
 * standard menu UI.
 */
public class MenuBuilder implements Menu {
    private static final String LOGTAG = "MenuBuilder";

    private static final int[]  sCategoryToOrder = new int[] {
        1, /* No category */
        4, /* CONTAINER */
        5, /* SYSTEM */
        3, /* SECONDARY */
        2, /* ALTERNATIVE */
        0, /* SELECTED_ALTERNATIVE */
    };

    private final Context mContext;
    private final Resources mResources;

    /**
     * Whether the shortcuts should be qwerty-accessible. Use isQwertyMode()
     * instead of accessing this directly.
     */
    private boolean mQwertyMode;

    /**
     * Whether the shortcuts should be visible on menus. Use isShortcutsVisible()
     * instead of accessing this directly.
     */ 
    private boolean mShortcutsVisible;
    
    /**
     * Callback that will receive the various menu-related events generated by
     * this class. Use getCallback to get a reference to the callback.
     */
    private Callback mCallback;
    
    /** Contains all of the items for this menu */
    private ArrayList<MenuItemImpl> mItems;

    /** Contains only the items that are currently visible.  This will be created/refreshed from
     * {@link #getVisibleItems()} */
    private ArrayList<MenuItemImpl> mVisibleItems;
    /**
     * Whether or not the items (or any one item's shown state) has changed since it was last
     * fetched from {@link #getVisibleItems()}
     */ 
    private boolean mIsVisibleItemsStale;
    
    /**
     * Contains only the items that should appear in the Action Bar, if present.
     */
    private ArrayList<MenuItemImpl> mActionItems;
    /**
     * Contains items that should NOT appear in the Action Bar, if present.
     */
    private ArrayList<MenuItemImpl> mNonActionItems;

    /**
     * Whether or not the items (or any one item's action state) has changed since it was
     * last fetched.
     */
    private boolean mIsActionItemsStale;

    /**
     * Default value for how added items should show in the action list.
     */
    private int mDefaultShowAsAction = MenuItem.SHOW_AS_ACTION_NEVER;

    /**
     * Current use case is Context Menus: As Views populate the context menu, each one has
     * extra information that should be passed along.  This is the current menu info that
     * should be set on all items added to this menu.
     */
    private ContextMenuInfo mCurrentMenuInfo;
    
    /** Header title for menu types that have a header (context and submenus) */
    CharSequence mHeaderTitle;
    /** Header icon for menu types that have a header and support icons (context) */
    Drawable mHeaderIcon;
    /** Header custom view for menu types that have a header and support custom views (context) */
    View mHeaderView;

    /**
     * Contains the state of the View hierarchy for all menu views when the menu
     * was frozen.
     */
    private SparseArray<Parcelable> mFrozenViewStates;

    /**
     * Prevents onItemsChanged from doing its junk, useful for batching commands
     * that may individually call onItemsChanged.
     */
    private boolean mPreventDispatchingItemsChanged = false;
    private boolean mItemsChangedWhileDispatchPrevented = false;
    
    private boolean mOptionalIconsVisible = false;

    private boolean mIsClosing = false;

    private ArrayList<MenuItemImpl> mTempShortcutItemList = new ArrayList<MenuItemImpl>();

    private CopyOnWriteArrayList<WeakReference<MenuPresenter>> mPresenters =
            new CopyOnWriteArrayList<WeakReference<MenuPresenter>>();
    
    /**
     * Called by menu to notify of close and selection changes.
     */
    public interface Callback {
        /**
         * Called when a menu item is selected.
         * @param menu The menu that is the parent of the item
         * @param item The menu item that is selected
         * @return whether the menu item selection was handled
         */
        public boolean onMenuItemSelected(MenuBuilder menu, MenuItem item);
        
        /**
         * Called when the mode of the menu changes (for example, from icon to expanded).
         * 
         * @param menu the menu that has changed modes
         */
        public void onMenuModeChange(MenuBuilder menu);
    }

    /**
     * Called by menu items to execute their associated action
     */
    public interface ItemInvoker {
        public boolean invokeItem(MenuItemImpl item);
    }

    public MenuBuilder(Context context) {
        mContext = context;
        mResources = context.getResources();
        
        mItems = new ArrayList<MenuItemImpl>();
        
        mVisibleItems = new ArrayList<MenuItemImpl>();
        mIsVisibleItemsStale = true;
        
        mActionItems = new ArrayList<MenuItemImpl>();
        mNonActionItems = new ArrayList<MenuItemImpl>();
        mIsActionItemsStale = true;
        
        setShortcutsVisibleInner(true);
    }
    
    public MenuBuilder setDefaultShowAsAction(int defaultShowAsAction) {
        mDefaultShowAsAction = defaultShowAsAction;
        return this;
    }

    /**
     * Add a presenter to this menu. This will only hold a WeakReference;
     * you do not need to explicitly remove a presenter, but you can using
     * {@link #removeMenuPresenter(MenuPresenter)}.
     *
     * @param presenter The presenter to add
     */
    public void addMenuPresenter(MenuPresenter presenter) {
        mPresenters.add(new WeakReference<MenuPresenter>(presenter));
        presenter.initForMenu(mContext, this);
        mIsActionItemsStale = true;
    }

    /**
     * Remove a presenter from this menu. That presenter will no longer
     * receive notifications of updates to this menu's data.
     *
     * @param presenter The presenter to remove
     */
    public void removeMenuPresenter(MenuPresenter presenter) {
        for (WeakReference<MenuPresenter> ref : mPresenters) {
            final MenuPresenter item = ref.get();
            if (item == null || item == presenter) {
                mPresenters.remove(ref);
            }
        }
    }
    
    private void dispatchPresenterUpdate(boolean cleared) {
        if (mPresenters.isEmpty()) return;

        stopDispatchingItemsChanged();
        for (WeakReference<MenuPresenter> ref : mPresenters) {
            final MenuPresenter presenter = ref.get();
            if (presenter == null) {
                mPresenters.remove(ref);
            } else {
                presenter.updateMenuView(cleared);
            }
        }
        startDispatchingItemsChanged();
    }
    
    private boolean dispatchSubMenuSelected(SubMenuBuilder subMenu) {
        if (mPresenters.isEmpty()) return false;

        boolean result = false;

        for (WeakReference<MenuPresenter> ref : mPresenters) {
            final MenuPresenter presenter = ref.get();
            if (presenter == null) {
                mPresenters.remove(ref);
            } else if (!result) {
                result = presenter.onSubMenuSelected(subMenu);
            }
        }
        return result;
    }

    public void setCallback(Callback cb) {
        mCallback = cb;
    }
    
    /**
     * Adds an item to the menu.  The other add methods funnel to this.
     */
    private MenuItem addInternal(int group, int id, int categoryOrder, CharSequence title) {
        final int ordering = getOrdering(categoryOrder);
        
        final MenuItemImpl item = new MenuItemImpl(this, group, id, categoryOrder,
                ordering, title, mDefaultShowAsAction);

        if (mCurrentMenuInfo != null) {
            // Pass along the current menu info
            item.setMenuInfo(mCurrentMenuInfo);
        }
        
        mItems.add(findInsertIndex(mItems, ordering), item);
        onItemsChanged(true);
        
        return item;
    }
    
    public MenuItem add(CharSequence title) {
        return addInternal(0, 0, 0, title);
    }

    public MenuItem add(int titleRes) {
        return addInternal(0, 0, 0, mResources.getString(titleRes));
    }

    public MenuItem add(int group, int id, int categoryOrder, CharSequence title) {
        return addInternal(group, id, categoryOrder, title);
    }

    public MenuItem add(int group, int id, int categoryOrder, int title) {
        return addInternal(group, id, categoryOrder, mResources.getString(title));
    }

    public SubMenu addSubMenu(CharSequence title) {
        return addSubMenu(0, 0, 0, title);
    }

    public SubMenu addSubMenu(int titleRes) {
        return addSubMenu(0, 0, 0, mResources.getString(titleRes));
    }

    public SubMenu addSubMenu(int group, int id, int categoryOrder, CharSequence title) {
        final MenuItemImpl item = (MenuItemImpl) addInternal(group, id, categoryOrder, title);
        final SubMenuBuilder subMenu = new SubMenuBuilder(mContext, this, item);
        item.setSubMenu(subMenu);
        
        return subMenu;
    }

    public SubMenu addSubMenu(int group, int id, int categoryOrder, int title) {
        return addSubMenu(group, id, categoryOrder, mResources.getString(title));
    }

    public int addIntentOptions(int group, int id, int categoryOrder, ComponentName caller,
            Intent[] specifics, Intent intent, int flags, MenuItem[] outSpecificItems) {
        PackageManager pm = mContext.getPackageManager();
        final List<ResolveInfo> lri =
                pm.queryIntentActivityOptions(caller, specifics, intent, 0);
        final int N = lri != null ? lri.size() : 0;

        if ((flags & FLAG_APPEND_TO_GROUP) == 0) {
            removeGroup(group);
        }

        for (int i=0; i<N; i++) {
            final ResolveInfo ri = lri.get(i);
            Intent rintent = new Intent(
                ri.specificIndex < 0 ? intent : specifics[ri.specificIndex]);
            rintent.setComponent(new ComponentName(
                    ri.activityInfo.applicationInfo.packageName,
                    ri.activityInfo.name));
            final MenuItem item = add(group, id, categoryOrder, ri.loadLabel(pm))
                    .setIcon(ri.loadIcon(pm))
                    .setIntent(rintent);
            if (outSpecificItems != null && ri.specificIndex >= 0) {
                outSpecificItems[ri.specificIndex] = item;
            }
        }

        return N;
    }

    public void removeItem(int id) {
        removeItemAtInt(findItemIndex(id), true);
    }

    public void removeGroup(int group) {
        final int i = findGroupIndex(group);

        if (i >= 0) {
            final int maxRemovable = mItems.size() - i;
            int numRemoved = 0;
            while ((numRemoved++ < maxRemovable) && (mItems.get(i).getGroupId() == group)) {
                // Don't force update for each one, this method will do it at the end
                removeItemAtInt(i, false);
            }
            
            // Notify menu views
            onItemsChanged(true);
        }
    }

    /**
     * Remove the item at the given index and optionally forces menu views to
     * update.
     * 
     * @param index The index of the item to be removed. If this index is
     *            invalid an exception is thrown.
     * @param updateChildrenOnMenuViews Whether to force update on menu views.
     *            Please make sure you eventually call this after your batch of
     *            removals.
     */
    private void removeItemAtInt(int index, boolean updateChildrenOnMenuViews) {
        if ((index < 0) || (index >= mItems.size())) return;

        mItems.remove(index);
        
        if (updateChildrenOnMenuViews) onItemsChanged(true);
    }
    
    public void removeItemAt(int index) {
        removeItemAtInt(index, true);
    }

    public void clearAll() {
        mPreventDispatchingItemsChanged = true;
        clear();
        clearHeader();
        mPreventDispatchingItemsChanged = false;
        mItemsChangedWhileDispatchPrevented = false;
        onItemsChanged(true);
    }
    
    public void clear() {
        mItems.clear();
        
        onItemsChanged(true);
    }

    void setExclusiveItemChecked(MenuItem item) {
        final int group = item.getGroupId();
        
        final int N = mItems.size();
        for (int i = 0; i < N; i++) {
            MenuItemImpl curItem = mItems.get(i);
            if (curItem.getGroupId() == group) {
                if (!curItem.isExclusiveCheckable()) continue;
                if (!curItem.isCheckable()) continue;
                
                // Check the item meant to be checked, uncheck the others (that are in the group)
                curItem.setCheckedInt(curItem == item);
            }
        }
    }
    
    public void setGroupCheckable(int group, boolean checkable, boolean exclusive) {
        final int N = mItems.size();
       
        for (int i = 0; i < N; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.getGroupId() == group) {
                item.setExclusiveCheckable(exclusive);
                item.setCheckable(checkable);
            }
        }
    }

    public void setGroupVisible(int group, boolean visible) {
        final int N = mItems.size();

        // We handle the notification of items being changed ourselves, so we use setVisibleInt rather
        // than setVisible and at the end notify of items being changed
        
        boolean changedAtLeastOneItem = false;
        for (int i = 0; i < N; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.getGroupId() == group) {
                if (item.setVisibleInt(visible)) changedAtLeastOneItem = true;
            }
        }

        if (changedAtLeastOneItem) onItemsChanged(false);
    }

    public void setGroupEnabled(int group, boolean enabled) {
        final int N = mItems.size();

        for (int i = 0; i < N; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.getGroupId() == group) {
                item.setEnabled(enabled);
            }
        }
    }

    public boolean hasVisibleItems() {
        final int size = size();

        for (int i = 0; i < size; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.isVisible()) {
                return true;
            }
        }

        return false;
    }

    public MenuItem findItem(int id) {
        final int size = size();
        for (int i = 0; i < size; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.getItemId() == id) {
                return item;
            } else if (item.hasSubMenu()) {
                MenuItem possibleItem = item.getSubMenu().findItem(id);
                
                if (possibleItem != null) {
                    return possibleItem;
                }
            }
        }
        
        return null;
    }

    public int findItemIndex(int id) {
        final int size = size();

        for (int i = 0; i < size; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.getItemId() == id) {
                return i;
            }
        }

        return -1;
    }

    public int findGroupIndex(int group) {
        return findGroupIndex(group, 0);
    }

    public int findGroupIndex(int group, int start) {
        final int size = size();
        
        if (start < 0) {
            start = 0;
        }
        
        for (int i = start; i < size; i++) {
            final MenuItemImpl item = mItems.get(i);
            
            if (item.getGroupId() == group) {
                return i;
            }
        }

        return -1;
    }
    
    public int size() {
        return mItems.size();
    }

    /** {@inheritDoc} */
    public MenuItem getItem(int index) {
        return mItems.get(index);
    }

    public boolean isShortcutKey(int keyCode, KeyEvent event) {
        return findItemWithShortcutForKey(keyCode, event) != null;
    }

    public void setQwertyMode(boolean isQwerty) {
        mQwertyMode = isQwerty;

        onItemsChanged(false);
    }

    /**
     * Returns the ordering across all items. This will grab the category from
     * the upper bits, find out how to order the category with respect to other
     * categories, and combine it with the lower bits.
     * 
     * @param categoryOrder The category order for a particular item (if it has
     *            not been or/add with a category, the default category is
     *            assumed).
     * @return An ordering integer that can be used to order this item across
     *         all the items (even from other categories).
     */
    private static int getOrdering(int categoryOrder) {
        final int index = (categoryOrder & CATEGORY_MASK) >> CATEGORY_SHIFT;
        
        if (index < 0 || index >= sCategoryToOrder.length) {
            throw new IllegalArgumentException("order does not contain a valid category.");
        }
        
        return (sCategoryToOrder[index] << CATEGORY_SHIFT) | (categoryOrder & USER_MASK);
    }

    /**
     * @return whether the menu shortcuts are in qwerty mode or not
     */
    boolean isQwertyMode() {
        return mQwertyMode;
    }

    /**
     * Sets whether the shortcuts should be visible on menus.  Devices without hardware
     * key input will never make shortcuts visible even if this method is passed 'true'.
     * 
     * @param shortcutsVisible Whether shortcuts should be visible (if true and a
     *            menu item does not have a shortcut defined, that item will
     *            still NOT show a shortcut)
     */
    public void setShortcutsVisible(boolean shortcutsVisible) {
        if (mShortcutsVisible == shortcutsVisible) return;

        setShortcutsVisibleInner(shortcutsVisible);
        onItemsChanged(false);
    }

    private void setShortcutsVisibleInner(boolean shortcutsVisible) {
        mShortcutsVisible = shortcutsVisible
                && mResources.getConfiguration().keyboard != Configuration.KEYBOARD_NOKEYS
                && mResources.getBoolean(
                        com.android.internal.R.bool.config_showMenuShortcutsWhenKeyboardPresent);
    }

    /**
     * @return Whether shortcuts should be visible on menus.
     */
    public boolean isShortcutsVisible() {
        return mShortcutsVisible;
    }
    
    Resources getResources() {
        return mResources;
    }
    
    public Context getContext() {
        return mContext;
    }
    
    boolean dispatchMenuItemSelected(MenuBuilder menu, MenuItem item) {
        return mCallback != null && mCallback.onMenuItemSelected(menu, item);
    }

    /**
     * Dispatch a mode change event to this menu's callback.
     */
    public void changeMenuMode() {
        if (mCallback != null) {
            mCallback.onMenuModeChange(this);
        }
    }

    private static int findInsertIndex(ArrayList<MenuItemImpl> items, int ordering) {
        for (int i = items.size() - 1; i >= 0; i--) {
            MenuItemImpl item = items.get(i);
            if (item.getOrdering() <= ordering) {
                return i + 1;
            }
        }
        
        return 0;
    }
    
    public boolean performShortcut(int keyCode, KeyEvent event, int flags) {
        final MenuItemImpl item = findItemWithShortcutForKey(keyCode, event);

        boolean handled = false;
        
        if (item != null) {
            handled = performItemAction(item, flags);
        }
        
        if ((flags & FLAG_ALWAYS_PERFORM_CLOSE) != 0) {
            close(true);
        }
        
        return handled;
    }

    /*
     * This function will return all the menu and sub-menu items that can
     * be directly (the shortcut directly corresponds) and indirectly
     * (the ALT-enabled char corresponds to the shortcut) associated
     * with the keyCode.
     */
    void findItemsWithShortcutForKey(List<MenuItemImpl> items, int keyCode, KeyEvent event) {
        final boolean qwerty = isQwertyMode();
        final int metaState = event.getMetaState();
        final KeyCharacterMap.KeyData possibleChars = new KeyCharacterMap.KeyData();
        // Get the chars associated with the keyCode (i.e using any chording combo)
        final boolean isKeyCodeMapped = event.getKeyData(possibleChars);
        // The delete key is not mapped to '\b' so we treat it specially
        if (!isKeyCodeMapped && (keyCode != KeyEvent.KEYCODE_DEL)) {
            return;
        }

        // Look for an item whose shortcut is this key.
        final int N = mItems.size();
        for (int i = 0; i < N; i++) {
            MenuItemImpl item = mItems.get(i);
            if (item.hasSubMenu()) {
                ((MenuBuilder)item.getSubMenu()).findItemsWithShortcutForKey(items, keyCode, event);
            }
            final char shortcutChar = qwerty ? item.getAlphabeticShortcut() : item.getNumericShortcut();
            if (((metaState & (KeyEvent.META_SHIFT_ON | KeyEvent.META_SYM_ON)) == 0) &&
                  (shortcutChar != 0) &&
                  (shortcutChar == possibleChars.meta[0]
                      || shortcutChar == possibleChars.meta[2]
                      || (qwerty && shortcutChar == '\b' &&
                          keyCode == KeyEvent.KEYCODE_DEL)) &&
                  item.isEnabled()) {
                items.add(item);
            }
        }
    }

    /*
     * We want to return the menu item associated with the key, but if there is no
     * ambiguity (i.e. there is only one menu item corresponding to the key) we want
     * to return it even if it's not an exact match; this allow the user to
     * _not_ use the ALT key for example, making the use of shortcuts slightly more
     * user-friendly. An example is on the G1, '!' and '1' are on the same key, and
     * in Gmail, Menu+1 will trigger Menu+! (the actual shortcut).
     *
     * On the other hand, if two (or more) shortcuts corresponds to the same key,
     * we have to only return the exact match.
     */
    MenuItemImpl findItemWithShortcutForKey(int keyCode, KeyEvent event) {
        // Get all items that can be associated directly or indirectly with the keyCode
        ArrayList<MenuItemImpl> items = mTempShortcutItemList;
        items.clear();
        findItemsWithShortcutForKey(items, keyCode, event);

        if (items.isEmpty()) {
            return null;
        }

        final int metaState = event.getMetaState();
        final KeyCharacterMap.KeyData possibleChars = new KeyCharacterMap.KeyData();
        // Get the chars associated with the keyCode (i.e using any chording combo)
        event.getKeyData(possibleChars);

        // If we have only one element, we can safely returns it
        final int size = items.size();
        if (size == 1) {
            return items.get(0);
        }

        final boolean qwerty = isQwertyMode();
        // If we found more than one item associated with the key,
        // we have to return the exact match
        for (int i = 0; i < size; i++) {
            final MenuItemImpl item = items.get(i);
            final char shortcutChar = qwerty ? item.getAlphabeticShortcut() :
                    item.getNumericShortcut();
            if ((shortcutChar == possibleChars.meta[0] &&
                    (metaState & KeyEvent.META_ALT_ON) == 0)
                || (shortcutChar == possibleChars.meta[2] &&
                    (metaState & KeyEvent.META_ALT_ON) != 0)
                || (qwerty && shortcutChar == '\b' &&
                    keyCode == KeyEvent.KEYCODE_DEL)) {
                return item;
            }
        }
        return null;
    }

    public boolean performIdentifierAction(int id, int flags) {
        // Look for an item whose identifier is the id.
        return performItemAction(findItem(id), flags);           
    }

    public boolean performItemAction(MenuItem item, int flags) {
        MenuItemImpl itemImpl = (MenuItemImpl) item;
        
        if (itemImpl == null || !itemImpl.isEnabled()) {
            return false;
        }        
        
        boolean invoked = itemImpl.invoke();

        if (item.hasSubMenu()) {
            close(false);

            invoked |= dispatchSubMenuSelected((SubMenuBuilder) item.getSubMenu());
            if (!invoked) close(true);
        } else {
            if ((flags & FLAG_PERFORM_NO_CLOSE) == 0) {
                close(true);
            }
        }
        
        return invoked;
    }
    
    /**
     * Closes the visible menu.
     * 
     * @param allMenusAreClosing Whether the menus are completely closing (true),
     *            or whether there is another menu coming in this menu's place
     *            (false). For example, if the menu is closing because a
     *            sub menu is about to be shown, <var>allMenusAreClosing</var>
     *            is false.
     */
    final void close(boolean allMenusAreClosing) {
        if (mIsClosing) return;

        mIsClosing = true;
        for (WeakReference<MenuPresenter> ref : mPresenters) {
            final MenuPresenter presenter = ref.get();
            if (presenter == null) {
                mPresenters.remove(ref);
            } else {
                presenter.onCloseMenu(this, allMenusAreClosing);
            }
        }
        mIsClosing = false;
    }

    /** {@inheritDoc} */
    public void close() {
        close(true);
    }

    /**
     * Called when an item is added or removed.
     * 
     * @param structureChanged true if the menu structure changed,
     *                         false if only item properties changed.
     */
    void onItemsChanged(boolean structureChanged) {
        if (!mPreventDispatchingItemsChanged) {
            if (structureChanged) {
                mIsVisibleItemsStale = true;
                mIsActionItemsStale = true;
            }

            dispatchPresenterUpdate(structureChanged);
        } else {
            mItemsChangedWhileDispatchPrevented = true;
        }
    }

    /**
     * Stop dispatching item changed events to presenters until
     * {@link #startDispatchingItemsChanged()} is called. Useful when
     * many menu operations are going to be performed as a batch.
     */
    public void stopDispatchingItemsChanged() {
        if (!mPreventDispatchingItemsChanged) {
            mPreventDispatchingItemsChanged = true;
            mItemsChangedWhileDispatchPrevented = false;
        }
    }

    public void startDispatchingItemsChanged() {
        mPreventDispatchingItemsChanged = false;

        if (mItemsChangedWhileDispatchPrevented) {
            mItemsChangedWhileDispatchPrevented = false;
            onItemsChanged(true);
        }
    }

    /**
     * Called by {@link MenuItemImpl} when its visible flag is changed.
     * @param item The item that has gone through a visibility change.
     */
    void onItemVisibleChanged(MenuItemImpl item) {
        // Notify of items being changed
        mIsVisibleItemsStale = true;
        onItemsChanged(false);
    }
    
    /**
     * Called by {@link MenuItemImpl} when its action request status is changed.
     * @param item The item that has gone through a change in action request status.
     */
    void onItemActionRequestChanged(MenuItemImpl item) {
        // Notify of items being changed
        mIsActionItemsStale = true;
        onItemsChanged(false);
    }
    
    ArrayList<MenuItemImpl> getVisibleItems() {
        if (!mIsVisibleItemsStale) return mVisibleItems;
        
        // Refresh the visible items
        mVisibleItems.clear();
        
        final int itemsSize = mItems.size(); 
        MenuItemImpl item;
        for (int i = 0; i < itemsSize; i++) {
            item = mItems.get(i);
            if (item.isVisible()) mVisibleItems.add(item);
        }
        
        mIsVisibleItemsStale = false;
        mIsActionItemsStale = true;
        
        return mVisibleItems;
    }

    /**
     * This method determines which menu items get to be 'action items' that will appear
     * in an action bar and which items should be 'overflow items' in a secondary menu.
     * The rules are as follows:
     *
     * <p>Items are considered for inclusion in the order specified within the menu.
     * There is a limit of mMaxActionItems as a total count, optionally including the overflow
     * menu button itself. This is a soft limit; if an item shares a group ID with an item
     * previously included as an action item, the new item will stay with its group and become
     * an action item itself even if it breaks the max item count limit. This is done to
     * limit the conceptual complexity of the items presented within an action bar. Only a few
     * unrelated concepts should be presented to the user in this space, and groups are treated
     * as a single concept.
     *
     * <p>There is also a hard limit of consumed measurable space: mActionWidthLimit. This
     * limit may be broken by a single item that exceeds the remaining space, but no further
     * items may be added. If an item that is part of a group cannot fit within the remaining
     * measured width, the entire group will be demoted to overflow. This is done to ensure room
     * for navigation and other affordances in the action bar as well as reduce general UI clutter.
     *
     * <p>The space freed by demoting a full group cannot be consumed by future menu items.
     * Once items begin to overflow, all future items become overflow items as well. This is
     * to avoid inadvertent reordering that may break the app's intended design.
     */
    public void flagActionItems() {
        if (!mIsActionItemsStale) {
            return;
        }

        // Presenters flag action items as needed.
        boolean flagged = false;
        for (WeakReference<MenuPresenter> ref : mPresenters) {
            final MenuPresenter presenter = ref.get();
            if (presenter == null) {
                mPresenters.remove(ref);
            } else {
                flagged |= presenter.flagActionItems();
            }
        }

        if (flagged) {
            mActionItems.clear();
            mNonActionItems.clear();
            ArrayList<MenuItemImpl> visibleItems = getVisibleItems();
            final int itemsSize = visibleItems.size();
            for (int i = 0; i < itemsSize; i++) {
                MenuItemImpl item = visibleItems.get(i);
                if (item.isActionButton()) {
                    mActionItems.add(item);
                } else {
                    mNonActionItems.add(item);
                }
            }
        } else if (mActionItems.size() + mNonActionItems.size() != getVisibleItems().size()) {
            // Nobody flagged anything, but if something doesn't add up then treat everything
            // as non-action items.
            // (This happens during a first pass with no action-item presenters.)
            mActionItems.clear();
            mNonActionItems.clear();
            mNonActionItems.addAll(getVisibleItems());
        }
        mIsActionItemsStale = false;
    }
    
    ArrayList<MenuItemImpl> getActionItems() {
        flagActionItems();
        return mActionItems;
    }
    
    ArrayList<MenuItemImpl> getNonActionItems() {
        flagActionItems();
        return mNonActionItems;
    }

    public void clearHeader() {
        mHeaderIcon = null;
        mHeaderTitle = null;
        mHeaderView = null;
        
        onItemsChanged(false);
    }
    
    private void setHeaderInternal(final int titleRes, final CharSequence title, final int iconRes,
            final Drawable icon, final View view) {
        final Resources r = getResources();

        if (view != null) {
            mHeaderView = view;
            
            // If using a custom view, then the title and icon aren't used
            mHeaderTitle = null;
            mHeaderIcon = null;
        } else {
            if (titleRes > 0) {
                mHeaderTitle = r.getText(titleRes);
            } else if (title != null) {
                mHeaderTitle = title;
            }
            
            if (iconRes > 0) {
                mHeaderIcon = r.getDrawable(iconRes);
            } else if (icon != null) {
                mHeaderIcon = icon;
            }
            
            // If using the title or icon, then a custom view isn't used
            mHeaderView = null;
        }
        
        // Notify of change
        onItemsChanged(false);
    }

    /**
     * Sets the header's title. This replaces the header view. Called by the
     * builder-style methods of subclasses.
     * 
     * @param title The new title.
     * @return This MenuBuilder so additional setters can be called.
     */
    protected MenuBuilder setHeaderTitleInt(CharSequence title) {
        setHeaderInternal(0, title, 0, null, null);
        return this;
    }
    
    /**
     * Sets the header's title. This replaces the header view. Called by the
     * builder-style methods of subclasses.
     * 
     * @param titleRes The new title (as a resource ID).
     * @return This MenuBuilder so additional setters can be called.
     */
    protected MenuBuilder setHeaderTitleInt(int titleRes) {
        setHeaderInternal(titleRes, null, 0, null, null);
        return this;
    }
    
    /**
     * Sets the header's icon. This replaces the header view. Called by the
     * builder-style methods of subclasses.
     * 
     * @param icon The new icon.
     * @return This MenuBuilder so additional setters can be called.
     */
    protected MenuBuilder setHeaderIconInt(Drawable icon) {
        setHeaderInternal(0, null, 0, icon, null);
        return this;
    }
    
    /**
     * Sets the header's icon. This replaces the header view. Called by the
     * builder-style methods of subclasses.
     * 
     * @param iconRes The new icon (as a resource ID).
     * @return This MenuBuilder so additional setters can be called.
     */
    protected MenuBuilder setHeaderIconInt(int iconRes) {
        setHeaderInternal(0, null, iconRes, null, null);
        return this;
    }
    
    /**
     * Sets the header's view. This replaces the title and icon. Called by the
     * builder-style methods of subclasses.
     * 
     * @param view The new view.
     * @return This MenuBuilder so additional setters can be called.
     */
    protected MenuBuilder setHeaderViewInt(View view) {
        setHeaderInternal(0, null, 0, null, view);
        return this;
    }
    
    public CharSequence getHeaderTitle() {
        return mHeaderTitle;
    }
    
    public Drawable getHeaderIcon() {
        return mHeaderIcon;
    }
    
    public View getHeaderView() {
        return mHeaderView;
    }
    
    /**
     * Gets the root menu (if this is a submenu, find its root menu).
     * @return The root menu.
     */
    public MenuBuilder getRootMenu() {
        return this;
    }
    
    /**
     * Sets the current menu info that is set on all items added to this menu
     * (until this is called again with different menu info, in which case that
     * one will be added to all subsequent item additions).
     * 
     * @param menuInfo The extra menu information to add.
     */
    public void setCurrentMenuInfo(ContextMenuInfo menuInfo) {
        mCurrentMenuInfo = menuInfo;
    }

    void setOptionalIconsVisible(boolean visible) {
        mOptionalIconsVisible = visible;
    }
    
    boolean getOptionalIconsVisible() {
        return mOptionalIconsVisible;
    }
}