1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.internal.view.menu;
18
19import android.annotation.NonNull;
20import android.annotation.Nullable;
21import android.content.Context;
22import android.os.Parcelable;
23import android.view.ViewGroup;
24
25/**
26 * A MenuPresenter is responsible for building views for a Menu object.
27 * It takes over some responsibility from the old style monolithic MenuBuilder class.
28 */
29public interface MenuPresenter {
30    /**
31     * Called by menu implementation to notify another component of open/close events.
32     */
33    public interface Callback {
34        /**
35         * Called when a menu is closing.
36         * @param menu
37         * @param allMenusAreClosing
38         */
39        public void onCloseMenu(MenuBuilder menu, boolean allMenusAreClosing);
40
41        /**
42         * Called when a submenu opens. Useful for notifying the application
43         * of menu state so that it does not attempt to hide the action bar
44         * while a submenu is open or similar.
45         *
46         * @param subMenu Submenu currently being opened
47         * @return true if the Callback will handle presenting the submenu, false if
48         *         the presenter should attempt to do so.
49         */
50        public boolean onOpenSubMenu(MenuBuilder subMenu);
51    }
52
53    /**
54     * Initializes this presenter for the given context and menu.
55     * <p>
56     * This method is called by MenuBuilder when a presenter is added. See
57     * {@link MenuBuilder#addMenuPresenter(MenuPresenter)}.
58     *
59     * @param context the context for this presenter; used for view creation
60     *                and resource management, must be non-{@code null}
61     * @param menu the menu to host, or {@code null} to clear the hosted menu
62     */
63    public void initForMenu(@NonNull Context context, @Nullable MenuBuilder menu);
64
65    /**
66     * Retrieve a MenuView to display the menu specified in
67     * {@link #initForMenu(Context, MenuBuilder)}.
68     *
69     * @param root Intended parent of the MenuView.
70     * @return A freshly created MenuView.
71     */
72    public MenuView getMenuView(ViewGroup root);
73
74    /**
75     * Update the menu UI in response to a change. Called by
76     * MenuBuilder during the normal course of operation.
77     *
78     * @param cleared true if the menu was entirely cleared
79     */
80    public void updateMenuView(boolean cleared);
81
82    /**
83     * Set a callback object that will be notified of menu events
84     * related to this specific presentation.
85     * @param cb Callback that will be notified of future events
86     */
87    public void setCallback(Callback cb);
88
89    /**
90     * Called by Menu implementations to indicate that a submenu item
91     * has been selected. An active Callback should be notified, and
92     * if applicable the presenter should present the submenu.
93     *
94     * @param subMenu SubMenu being opened
95     * @return true if the the event was handled, false otherwise.
96     */
97    public boolean onSubMenuSelected(SubMenuBuilder subMenu);
98
99    /**
100     * Called by Menu implementations to indicate that a menu or submenu is
101     * closing. Presenter implementations should close the representation
102     * of the menu indicated as necessary and notify a registered callback.
103     *
104     * @param menu the menu or submenu that is closing
105     * @param allMenusAreClosing {@code true} if all displayed menus and
106     *                           submenus are closing, {@code false} if only
107     *                           the specified menu is closing
108     */
109    public void onCloseMenu(MenuBuilder menu, boolean allMenusAreClosing);
110
111    /**
112     * Called by Menu implementations to flag items that will be shown as actions.
113     * @return true if this presenter changed the action status of any items.
114     */
115    public boolean flagActionItems();
116
117    /**
118     * Called when a menu item with a collapsable action view should expand its action view.
119     *
120     * @param menu Menu containing the item to be expanded
121     * @param item Item to be expanded
122     * @return true if this presenter expanded the action view, false otherwise.
123     */
124    public boolean expandItemActionView(MenuBuilder menu, MenuItemImpl item);
125
126    /**
127     * Called when a menu item with a collapsable action view should collapse its action view.
128     *
129     * @param menu Menu containing the item to be collapsed
130     * @param item Item to be collapsed
131     * @return true if this presenter collapsed the action view, false otherwise.
132     */
133    public boolean collapseItemActionView(MenuBuilder menu, MenuItemImpl item);
134
135    /**
136     * Returns an ID for determining how to save/restore instance state.
137     * @return a valid ID value.
138     */
139    public int getId();
140
141    /**
142     * Returns a Parcelable describing the current state of the presenter.
143     * It will be passed to the {@link #onRestoreInstanceState(Parcelable)}
144     * method of the presenter sharing the same ID later.
145     * @return The saved instance state
146     */
147    public Parcelable onSaveInstanceState();
148
149    /**
150     * Supplies the previously saved instance state to be restored.
151     * @param state The previously saved instance state
152     */
153    public void onRestoreInstanceState(Parcelable state);
154}
155