core/java/android/view/Menu.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 android.view;

import android.annotation.StringRes;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;

/**
 * Interface for managing the items in a menu.
 * <p>
 * By default, every Activity supports an options menu of actions or options.
 * You can add items to this menu and handle clicks on your additions. The
 * easiest way of adding menu items is inflating an XML file into the
 * {@link Menu} via {@link MenuInflater}. The easiest way of attaching code to
 * clicks is via {@link Activity#onOptionsItemSelected(MenuItem)} and
 * {@link Activity#onContextItemSelected(MenuItem)}.
 * <p>
 * Different menu types support different features:
 * <ol>
 * <li><b>Context menus</b>: Do not support item shortcuts and item icons.
 * <li><b>Options menus</b>: The <b>icon menus</b> do not support item check
 * marks and only show the item's
 * {@link MenuItem#setTitleCondensed(CharSequence) condensed title}. The
 * <b>expanded menus</b> (only available if six or more menu items are visible,
 * reached via the 'More' item in the icon menu) do not show item icons, and
 * item check marks are discouraged.
 * <li><b>Sub menus</b>: Do not support item icons, or nested sub menus.
 * </ol>
 *
 * <div class="special reference">
 * <h3>Developer Guides</h3>
 * <p>For more information about creating menus, read the
 * <a href="{@docRoot}guide/topics/ui/menus.html">Menus</a> developer guide.</p>
 * </div>
 */
public interface Menu {

    /**
     * This is the part of an order integer that the user can provide.
     * @hide
     */
    static final int USER_MASK = 0x0000ffff;
    /**
     * Bit shift of the user portion of the order integer.
     * @hide
     */
    static final int USER_SHIFT = 0;

    /**
     * This is the part of an order integer that supplies the category of the
     * item.
     * @hide
     */
    static final int CATEGORY_MASK = 0xffff0000;
    /**
     * Bit shift of the category portion of the order integer.
     * @hide
     */
    static final int CATEGORY_SHIFT = 16;

    /**
     * A mask of all supported modifiers for MenuItem's keyboard shortcuts
     */
    static final int SUPPORTED_MODIFIERS_MASK = KeyEvent.META_META_ON | KeyEvent.META_CTRL_ON
            | KeyEvent.META_ALT_ON | KeyEvent.META_SHIFT_ON | KeyEvent.META_SYM_ON
            | KeyEvent.META_FUNCTION_ON;

    /**
     * Value to use for group and item identifier integers when you don't care
     * about them.
     */
    static final int NONE = 0;

    /**
     * First value for group and item identifier integers.
     */
    static final int FIRST = 1;

    // Implementation note: Keep these CATEGORY_* in sync with the category enum
    // in attrs.xml

    /**
     * Category code for the order integer for items/groups that are part of a
     * container -- or/add this with your base value.
     */
    static final int CATEGORY_CONTAINER = 0x00010000;

    /**
     * Category code for the order integer for items/groups that are provided by
     * the system -- or/add this with your base value.
     */
    static final int CATEGORY_SYSTEM = 0x00020000;

    /**
     * Category code for the order integer for items/groups that are
     * user-supplied secondary (infrequently used) options -- or/add this with
     * your base value.
     */
    static final int CATEGORY_SECONDARY = 0x00030000;

    /**
     * Category code for the order integer for items/groups that are 
     * alternative actions on the data that is currently displayed -- or/add
     * this with your base value.
     */
    static final int CATEGORY_ALTERNATIVE = 0x00040000;

    /**
     * Flag for {@link #addIntentOptions}: if set, do not automatically remove
     * any existing menu items in the same group.
     */
    static final int FLAG_APPEND_TO_GROUP = 0x0001;

    /**
     * Flag for {@link #performShortcut}: if set, do not close the menu after
     * executing the shortcut.
     */
    static final int FLAG_PERFORM_NO_CLOSE = 0x0001;

    /**
     * Flag for {@link #performShortcut(int, KeyEvent, int)}: if set, always
     * close the menu after executing the shortcut. Closing the menu also resets
     * the prepared state.
     */
    static final int FLAG_ALWAYS_PERFORM_CLOSE = 0x0002;
    
    /**
     * Add a new item to the menu. This item displays the given title for its
     * label.
     * 
     * @param title The text to display for the item.
     * @return The newly added menu item.
     */
    public MenuItem add(CharSequence title);
    
    /**
     * Add a new item to the menu. This item displays the given title for its
     * label.
     * 
     * @param titleRes Resource identifier of title string.
     * @return The newly added menu item.
     */
    public MenuItem add(@StringRes int titleRes);

    /**
     * Add a new item to the menu. This item displays the given title for its
     * label.
     * 
     * @param groupId The group identifier that this item should be part of.
     *        This can be used to define groups of items for batch state
     *        changes. Normally use {@link #NONE} if an item should not be in a
     *        group.
     * @param itemId Unique item ID. Use {@link #NONE} if you do not need a
     *        unique ID.
     * @param order The order for the item. Use {@link #NONE} if you do not care
     *        about the order. See {@link MenuItem#getOrder()}.
     * @param title The text to display for the item.
     * @return The newly added menu item.
     */
    public MenuItem add(int groupId, int itemId, int order, CharSequence title);

    /**
     * Variation on {@link #add(int, int, int, CharSequence)} that takes a
     * string resource identifier instead of the string itself.
     * 
     * @param groupId The group identifier that this item should be part of.
     *        This can also be used to define groups of items for batch state
     *        changes. Normally use {@link #NONE} if an item should not be in a
     *        group.
     * @param itemId Unique item ID. Use {@link #NONE} if you do not need a
     *        unique ID.
     * @param order The order for the item. Use {@link #NONE} if you do not care
     *        about the order. See {@link MenuItem#getOrder()}.
     * @param titleRes Resource identifier of title string.
     * @return The newly added menu item.
     */
    public MenuItem add(int groupId, int itemId, int order, @StringRes int titleRes);

    /**
     * Add a new sub-menu to the menu. This item displays the given title for
     * its label. To modify other attributes on the submenu's menu item, use
     * {@link SubMenu#getItem()}.
     * 
     * @param title The text to display for the item.
     * @return The newly added sub-menu
     */
    SubMenu addSubMenu(final CharSequence title);

    /**
     * Add a new sub-menu to the menu. This item displays the given title for
     * its label. To modify other attributes on the submenu's menu item, use
     * {@link SubMenu#getItem()}.
     * 
     * @param titleRes Resource identifier of title string.
     * @return The newly added sub-menu
     */
    SubMenu addSubMenu(@StringRes final int titleRes);

    /**
     * Add a new sub-menu to the menu. This item displays the given
     * <var>title</var> for its label. To modify other attributes on the
     * submenu's menu item, use {@link SubMenu#getItem()}.
     *<p>
     * Note that you can only have one level of sub-menus, i.e. you cannnot add
     * a subMenu to a subMenu: An {@link UnsupportedOperationException} will be
     * thrown if you try.
     * 
     * @param groupId The group identifier that this item should be part of.
     *        This can also be used to define groups of items for batch state
     *        changes. Normally use {@link #NONE} if an item should not be in a
     *        group.
     * @param itemId Unique item ID. Use {@link #NONE} if you do not need a
     *        unique ID.
     * @param order The order for the item. Use {@link #NONE} if you do not care
     *        about the order. See {@link MenuItem#getOrder()}.
     * @param title The text to display for the item.
     * @return The newly added sub-menu
     */
    SubMenu addSubMenu(final int groupId, final int itemId, int order, final CharSequence title);

    /**
     * Variation on {@link #addSubMenu(int, int, int, CharSequence)} that takes
     * a string resource identifier for the title instead of the string itself.
     * 
     * @param groupId The group identifier that this item should be part of.
     *        This can also be used to define groups of items for batch state
     *        changes. Normally use {@link #NONE} if an item should not be in a group.
     * @param itemId Unique item ID. Use {@link #NONE} if you do not need a unique ID.
     * @param order The order for the item. Use {@link #NONE} if you do not care about the
     *        order. See {@link MenuItem#getOrder()}.
     * @param titleRes Resource identifier of title string.
     * @return The newly added sub-menu
     */
    SubMenu addSubMenu(int groupId, int itemId, int order, @StringRes int titleRes);

    /**
     * Add a group of menu items corresponding to actions that can be performed
     * for a particular Intent. The Intent is most often configured with a null
     * action, the data that the current activity is working with, and includes
     * either the {@link Intent#CATEGORY_ALTERNATIVE} or
     * {@link Intent#CATEGORY_SELECTED_ALTERNATIVE} to find activities that have
     * said they would like to be included as optional action. You can, however,
     * use any Intent you want.
     * 
     * <p>
     * See {@link android.content.pm.PackageManager#queryIntentActivityOptions}
     * for more * details on the <var>caller</var>, <var>specifics</var>, and
     * <var>intent</var> arguments. The list returned by that function is used
     * to populate the resulting menu items.
     * 
     * <p>
     * All of the menu items of possible options for the intent will be added
     * with the given group and id. You can use the group to control ordering of
     * the items in relation to other items in the menu. Normally this function
     * will automatically remove any existing items in the menu in the same
     * group and place a divider above and below the added items; this behavior
     * can be modified with the <var>flags</var> parameter. For each of the
     * generated items {@link MenuItem#setIntent} is called to associate the
     * appropriate Intent with the item; this means the activity will
     * automatically be started for you without having to do anything else.
     * 
     * @param groupId The group identifier that the items should be part of.
     *        This can also be used to define groups of items for batch state
     *        changes. Normally use {@link #NONE} if the items should not be in
     *        a group.
     * @param itemId Unique item ID. Use {@link #NONE} if you do not need a
     *        unique ID.
     * @param order The order for the items. Use {@link #NONE} if you do not
     *        care about the order. See {@link MenuItem#getOrder()}.
     * @param caller The current activity component name as defined by
     *        queryIntentActivityOptions().
     * @param specifics Specific items to place first as defined by
     *        queryIntentActivityOptions().
     * @param intent Intent describing the kinds of items to populate in the
     *        list as defined by queryIntentActivityOptions().
     * @param flags Additional options controlling how the items are added.
     * @param outSpecificItems Optional array in which to place the menu items
     *        that were generated for each of the <var>specifics</var> that were
     *        requested. Entries may be null if no activity was found for that
     *        specific action.
     * @return The number of menu items that were added.
     * 
     * @see #FLAG_APPEND_TO_GROUP
     * @see MenuItem#setIntent
     * @see android.content.pm.PackageManager#queryIntentActivityOptions
     */
    public int addIntentOptions(int groupId, int itemId, int order,
                                ComponentName caller, Intent[] specifics,
                                Intent intent, int flags, MenuItem[] outSpecificItems);

    /**
     * Remove the item with the given identifier.
     *
     * @param id The item to be removed.  If there is no item with this
     *           identifier, nothing happens.
     */
    public void removeItem(int id);

    /**
     * Remove all items in the given group.
     *
     * @param groupId The group to be removed.  If there are no items in this
     *           group, nothing happens.
     */
    public void removeGroup(int groupId);

    /**
     * Remove all existing items from the menu, leaving it empty as if it had
     * just been created.
     */
    public void clear();

    /**
     * Control whether a particular group of items can show a check mark.  This
     * is similar to calling {@link MenuItem#setCheckable} on all of the menu items
     * with the given group identifier, but in addition you can control whether
     * this group contains a mutually-exclusive set items.  This should be called
     * after the items of the group have been added to the menu.
     *
     * @param group The group of items to operate on.
     * @param checkable Set to true to allow a check mark, false to
     *                  disallow.  The default is false.
     * @param exclusive If set to true, only one item in this group can be
     *                  checked at a time; checking an item will automatically
     *                  uncheck all others in the group.  If set to false, each
     *                  item can be checked independently of the others.
     *
     * @see MenuItem#setCheckable
     * @see MenuItem#setChecked
     */
    public void setGroupCheckable(int group, boolean checkable, boolean exclusive);

    /**
     * Show or hide all menu items that are in the given group.
     *
     * @param group The group of items to operate on.
     * @param visible If true the items are visible, else they are hidden.
     *
     * @see MenuItem#setVisible
     */
    public void setGroupVisible(int group, boolean visible);
    
    /**
     * Enable or disable all menu items that are in the given group.
     *
     * @param group The group of items to operate on.
     * @param enabled If true the items will be enabled, else they will be disabled.
     *
     * @see MenuItem#setEnabled
     */
    public void setGroupEnabled(int group, boolean enabled);
    
    /**
     * Return whether the menu currently has item items that are visible.
     *
     * @return True if there is one or more item visible,
     *         else false.
     */
    public boolean hasVisibleItems();

    /**
     * Return the menu item with a particular identifier.
     *
     * @param id The identifier to find.
     *
     * @return The menu item object, or null if there is no item with
     *         this identifier.
     */
    public MenuItem findItem(int id);

    /**
     * Get the number of items in the menu.  Note that this will change any
     * times items are added or removed from the menu.
     *
     * @return The item count.
     */
    public int size();

    /**
     * Gets the menu item at the given index.
     * 
     * @param index The index of the menu item to return.
     * @return The menu item.
     * @exception IndexOutOfBoundsException
     *                when {@code index < 0 || >= size()}
     */
    public MenuItem getItem(int index);
    
    /**
     * Closes the menu, if open.
     */
    public void close();
    
    /**
     * Execute the menu item action associated with the given shortcut
     * character.
     *
     * @param keyCode The keycode of the shortcut key.
     * @param event Key event message.
     * @param flags Additional option flags or 0.
     *
     * @return If the given shortcut exists and is shown, returns
     *         true; else returns false.
     *
     * @see #FLAG_PERFORM_NO_CLOSE
     */
    public boolean performShortcut(int keyCode, KeyEvent event, int flags);

    /**
     * Is a keypress one of the defined shortcut keys for this window.
     * @param keyCode the key code from {@link KeyEvent} to check.
     * @param event the {@link KeyEvent} to use to help check.
     */
    boolean isShortcutKey(int keyCode, KeyEvent event);
    
    /**
     * Execute the menu item action associated with the given menu identifier.
     * 
     * @param id Identifier associated with the menu item. 
     * @param flags Additional option flags or 0.
     * 
     * @return If the given identifier exists and is shown, returns
     *         true; else returns false.
     * 
     * @see #FLAG_PERFORM_NO_CLOSE
     */
    public boolean performIdentifierAction(int id, int flags);


    /**
     * Control whether the menu should be running in qwerty mode (alphabetic
     * shortcuts) or 12-key mode (numeric shortcuts).
     * 
     * @param isQwerty If true the menu will use alphabetic shortcuts; else it
     *                 will use numeric shortcuts.
     */
    public void setQwertyMode(boolean isQwerty);

    /**
     * Enable or disable the group dividers.
     */
    default void setGroupDividerEnabled(boolean groupDividerEnabled) {
    }
}