core/java/android/app/ActionBar.java

/*
 * Copyright (C) 2010 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.app;

import android.graphics.drawable.Drawable;
import android.view.View;
import android.view.Window;
import android.widget.SpinnerAdapter;

/**
 * This is the public interface to the contextual ActionBar.
 * The ActionBar acts as a replacement for the title bar in Activities.
 * It provides facilities for creating toolbar actions as well as
 * methods of navigating around an application. 
 */
public abstract class ActionBar {
    /**
     * Standard navigation mode. Consists of either a logo or icon
     * and title text with an optional subtitle. Clicking any of these elements
     * will dispatch onActionItemSelected to the registered Callback with
     * a MenuItem with item ID android.R.id.home.
     */
    public static final int NAVIGATION_MODE_STANDARD = 0;
    
    /**
     * Dropdown list navigation mode. Instead of static title text this mode
     * presents a dropdown menu for navigation within the activity.
     */
    public static final int NAVIGATION_MODE_DROPDOWN_LIST = 1;
    
    /**
     * Tab navigation mode. Instead of static title text this mode
     * presents a series of tabs for navigation within the activity.
     */
    public static final int NAVIGATION_MODE_TABS = 2;
    
    /**
     * Custom navigation mode. This navigation mode is set implicitly whenever
     * a custom navigation view is set. See {@link #setCustomNavigationMode(View)}.
     */
    public static final int NAVIGATION_MODE_CUSTOM = 3;

    /**
     * Use logo instead of icon if available. This flag will cause appropriate
     * navigation modes to use a wider logo in place of the standard icon.
     */
    public static final int DISPLAY_USE_LOGO = 0x1;
    
    /**
     * Hide 'home' elements in this action bar, leaving more space for other
     * navigation elements. This includes logo and icon.
     */
    public static final int DISPLAY_HIDE_HOME = 0x2;

    /**
     * Set the action bar into custom navigation mode, supplying a view
     * for custom navigation.
     * 
     * Custom navigation views appear between the application icon and
     * any action buttons and may use any space available there. Common
     * use cases for custom navigation views might include an auto-suggesting
     * address bar for a browser or other navigation mechanisms that do not
     * translate well to provided navigation modes.
     * 
     * @param view Custom navigation view to place in the ActionBar.
     */
    public abstract void setCustomNavigationMode(View view);
    
    /**
     * Set the action bar into dropdown navigation mode and supply an adapter
     * that will provide views for navigation choices.
     * 
     * @param adapter An adapter that will provide views both to display
     *                the current navigation selection and populate views
     *                within the dropdown navigation menu.
     * @param callback A NavigationCallback that will receive events when the user
     *                 selects a navigation item.
     */
    public abstract void setDropdownNavigationMode(SpinnerAdapter adapter,
            NavigationCallback callback);

    /**
     * Set the action bar into dropdown navigation mode and supply an adapter that will
     * provide views for navigation choices.
     *
     * @param adapter An adapter that will provide views both to display the current
     *                navigation selection and populate views within the dropdown
     *                navigation menu.
     * @param callback A NavigationCallback that will receive events when the user
     *                 selects a navigation item.
     * @param defaultSelectedPosition Position within the provided adapter that should be
     *                                selected from the outset.
     */
    public abstract void setDropdownNavigationMode(SpinnerAdapter adapter,
            NavigationCallback callback, int defaultSelectedPosition);

    /**
     * Set the selected navigation item in dropdown or tabbed navigation modes.
     *
     * @param position Position of the item to select.
     */
    public abstract void setSelectedNavigationItem(int position);

    /**
     * Get the position of the selected navigation item in dropdown or tabbed navigation modes.
     *
     * @return Position of the selected item.
     */
    public abstract int getSelectedNavigationItem();

    /**
     * Set the action bar into standard navigation mode, using the currently set title
     * and/or subtitle.
     *
     * Standard navigation mode is default. The title is automatically set to the name of
     * your Activity on startup if an action bar is present.
     */
    public abstract void setStandardNavigationMode();

    /**
     * Set the action bar's title. This will only be displayed in standard navigation mode.
     *
     * @param title Title to set
     *
     * @see #setTitle(int)
     */
    public abstract void setTitle(CharSequence title);

    /**
     * Set the action bar's title. This will only be displayed in standard navigation mode.
     *
     * @param resId Resource ID of title string to set
     *
     * @see #setTitle(CharSequence)
     */
    public abstract void setTitle(int resId);

    /**
     * Set the action bar's subtitle. This will only be displayed in standard navigation mode.
     * Set to null to disable the subtitle entirely.
     *
     * @param subtitle Subtitle to set
     *
     * @see #setSubtitle(int)
     */
    public abstract void setSubtitle(CharSequence subtitle);

    /**
     * Set the action bar's subtitle. This will only be displayed in standard navigation mode.
     *
     * @param resId Resource ID of subtitle string to set
     *
     * @see #setSubtitle(CharSequence)
     */
    public abstract void setSubtitle(int resId);

    /**
     * Set display options. This changes all display option bits at once. To change
     * a limited subset of display options, see {@link #setDisplayOptions(int, int)}.
     * 
     * @param options A combination of the bits defined by the DISPLAY_ constants
     *                defined in ActionBar.
     */
    public abstract void setDisplayOptions(int options);
    
    /**
     * Set selected display options. Only the options specified by mask will be changed.
     * To change all display option bits at once, see {@link #setDisplayOptions(int)}.
     * 
     * <p>Example: setDisplayOptions(0, DISPLAY_HIDE_HOME) will disable the
     * {@link #DISPLAY_HIDE_HOME} option.
     * setDisplayOptions(DISPLAY_HIDE_HOME, DISPLAY_HIDE_HOME | DISPLAY_USE_LOGO)
     * will enable {@link #DISPLAY_HIDE_HOME} and disable {@link #DISPLAY_USE_LOGO}.
     * 
     * @param options A combination of the bits defined by the DISPLAY_ constants
     *                defined in ActionBar.
     * @param mask A bit mask declaring which display options should be changed.
     */
    public abstract void setDisplayOptions(int options, int mask);
    
    /**
     * Set the ActionBar's background.
     * 
     * @param d Background drawable
     */
    public abstract void setBackgroundDrawable(Drawable d);
    
    /**
     * @return The current custom navigation view.
     */
    public abstract View getCustomNavigationView();
    
    /**
     * Returns the current ActionBar title in standard mode.
     * Returns null if {@link #getNavigationMode()} would not return
     * {@link #NAVIGATION_MODE_STANDARD}. 
     *
     * @return The current ActionBar title or null.
     */
    public abstract CharSequence getTitle();
    
    /**
     * Returns the current ActionBar subtitle in standard mode.
     * Returns null if {@link #getNavigationMode()} would not return
     * {@link #NAVIGATION_MODE_STANDARD}. 
     *
     * @return The current ActionBar subtitle or null.
     */
    public abstract CharSequence getSubtitle();
    
    /**
     * Returns the current navigation mode. The result will be one of:
     * <ul>
     * <li>{@link #NAVIGATION_MODE_STANDARD}</li>
     * <li>{@link #NAVIGATION_MODE_DROPDOWN_LIST}</li>
     * <li>{@link #NAVIGATION_MODE_TABS}</li>
     * <li>{@link #NAVIGATION_MODE_CUSTOM}</li>
     * </ul>
     *
     * @return The current navigation mode.
     * 
     * @see #setStandardNavigationMode()
     * @see #setStandardNavigationMode(CharSequence)
     * @see #setStandardNavigationMode(CharSequence, CharSequence)
     * @see #setDropdownNavigationMode(SpinnerAdapter)
     * @see #setTabNavigationMode()
     * @see #setCustomNavigationMode(View)
     */
    public abstract int getNavigationMode();
    
    /**
     * @return The current set of display options. 
     */
    public abstract int getDisplayOptions();

    /**
     * Set the action bar into tabbed navigation mode.
     *
     * @see #addTab(Tab)
     * @see #insertTab(Tab, int)
     * @see #removeTab(Tab)
     * @see #removeTabAt(int)
     */
    public abstract void setTabNavigationMode();

    /**
     * Create and return a new {@link Tab}.
     * This tab will not be included in the action bar until it is added.
     *
     * @return A new Tab
     *
     * @see #addTab(Tab)
     * @see #insertTab(Tab, int)
     */
    public abstract Tab newTab();

    /**
     * Add a tab for use in tabbed navigation mode. The tab will be added at the end of the list.
     *
     * @param tab Tab to add
     */
    public abstract void addTab(Tab tab);

    /**
     * Add a tab for use in tabbed navigation mode. The tab will be inserted at
     * <code>position</code>.
     *
     * @param tab The tab to add
     * @param position The new position of the tab
     */
    public abstract void addTab(Tab tab, int position);

    /**
     * Remove a tab from the action bar.
     *
     * @param tab The tab to remove
     */
    public abstract void removeTab(Tab tab);

    /**
     * Remove a tab from the action bar.
     *
     * @param position Position of the tab to remove
     */
    public abstract void removeTabAt(int position);

    /**
     * Select the specified tab. If it is not a child of this action bar it will be added.
     *
     * @param tab Tab to select
     */
    public abstract void selectTab(Tab tab);

    /**
     * Returns the currently selected tab if in tabbed navigation mode and there is at least
     * one tab present.
     *
     * @return The currently selected tab or null
     */
    public abstract Tab getSelectedTab();

    /**
     * Retrieve the current height of the ActionBar.
     *
     * @return The ActionBar's height
     */
    public abstract int getHeight();

    /**
     * Show the ActionBar if it is not currently showing.
     * If the window hosting the ActionBar does not have the feature
     * {@link Window#FEATURE_ACTION_BAR_OVERLAY} it will resize application
     * content to fit the new space available.
     */
    public abstract void show();

    /**
     * Hide the ActionBar if it is not currently showing.
     * If the window hosting the ActionBar does not have the feature
     * {@link Window#FEATURE_ACTION_BAR_OVERLAY} it will resize application
     * content to fit the new space available.
     */
    public abstract void hide();

    /**
     * @return <code>true</code> if the ActionBar is showing, <code>false</code> otherwise.
     */
    public abstract boolean isShowing();

    /**
     * Callback interface for ActionBar navigation events. 
     */
    public interface NavigationCallback {
        /**
         * This method is called whenever a navigation item in your action bar
         * is selected.
         *    
         * @param itemPosition Position of the item clicked.
         * @param itemId ID of the item clicked.
         * @return True if the event was handled, false otherwise.
         */
        public boolean onNavigationItemSelected(int itemPosition, long itemId);
    }

    /**
     * A tab in the action bar.
     *
     * <p>Tabs manage the hiding and showing of {@link Fragment}s.
     */
    public static abstract class Tab {
        /**
         * An invalid position for a tab.
         *
         * @see #getPosition()
         */
        public static final int INVALID_POSITION = -1;

        /**
         * Return the current position of this tab in the action bar.
         *
         * @return Current position, or {@link #INVALID_POSITION} if this tab is not currently in
         *         the action bar.
         */
        public abstract int getPosition();

        /**
         * Return the icon associated with this tab.
         *
         * @return The tab's icon
         */
        public abstract Drawable getIcon();

        /**
         * Return the text of this tab.
         *
         * @return The tab's text
         */
        public abstract CharSequence getText();

        /**
         * Set the icon displayed on this tab.
         *
         * @param icon The drawable to use as an icon
         */
        public abstract void setIcon(Drawable icon);

        /**
         * Set the text displayed on this tab. Text may be truncated if there is not
         * room to display the entire string.
         *
         * @param text The text to display
         */
        public abstract void setText(CharSequence text);

        /**
         * Set a custom view to be used for this tab. This overrides values set by
         * {@link #setText(CharSequence)} and {@link #setIcon(Drawable)}.
         *
         * @param view Custom view to be used as a tab.
         */
        public abstract void setCustomView(View view);

        /**
         * Retrieve a previously set custom view for this tab.
         *
         * @return The custom view set by {@link #setCustomView(View)}.
         */
        public abstract View getCustomView();

        /**
         * Give this Tab an arbitrary object to hold for later use.
         *
         * @param obj Object to store
         */
        public abstract void setTag(Object obj);

        /**
         * @return This Tab's tag object.
         */
        public abstract Object getTag();

        /**
         * Set the {@link TabListener} that will handle switching to and from this tab.
         * All tabs must have a TabListener set before being added to the ActionBar.
         *
         * @param listener Listener to handle tab selection events
         */
        public abstract void setTabListener(TabListener listener);

        /**
         * Select this tab. Only valid if the tab has been added to the action bar.
         */
        public abstract void select();
    }

    /**
     * Callback interface invoked when a tab is focused, unfocused, added, or removed.
     */
    public interface TabListener {
        /**
         * Called when a tab enters the selected state.
         *
         * @param tab The tab that was selected
         * @param ft A {@link FragmentTransaction} for queuing fragment operations to execute
         *        during a tab switch. The previous tab's unselect and this tab's select will be
         *        executed in a single transaction.
         */
        public void onTabSelected(Tab tab, FragmentTransaction ft);

        /**
         * Called when a tab exits the selected state.
         *
         * @param tab The tab that was unselected
         * @param ft A {@link FragmentTransaction} for queuing fragment operations to execute
         *        during a tab switch. This tab's unselect and the newly selected tab's select
         *        will be executed in a single transaction.
         */
        public void onTabUnselected(Tab tab, FragmentTransaction ft);
    }
}