https://source.android.com/ 
/*
 * Copyright (C) 2011 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.content.Context;
import android.util.Log;


An ActionProvider defines rich menu interaction in a single component.
ActionProvider can generate action views for use in the action bar,
dynamically populate submenus of a MenuItem, and handle default menu
item invocations.

An ActionProvider can be optionally specified for a MenuItem and will be responsible for creating the action view that appears in the ActionBar in place of a simple button in the bar. When the menu item is presented in a way that does not allow custom action views, (e.g. in an overflow menu,) the ActionProvider can perform a default action.


There are two ways to use an action provider:

    

  •  Set the action provider on a MenuItem directly by calling MenuItem.setActionProvider(ActionProvider). 
    • 

  • 
Declare the action provider in an XML menu resource. For example:

    
  <item android:id="@+id/my_menu_item"
    android:title="Title"
    android:icon="@drawable/my_menu_item_icon"
    android:showAsAction="ifRoom"
    android:actionProviderClass="foo.bar.SomeActionProvider" />


    

    • 





See Also:
/**
 * An ActionProvider defines rich menu interaction in a single component.
 * ActionProvider can generate action views for use in the action bar,
 * dynamically populate submenus of a MenuItem, and handle default menu
 * item invocations.
 *
 * <p>An ActionProvider can be optionally specified for a {@link MenuItem} and will be
 * responsible for creating the action view that appears in the {@link android.app.ActionBar}
 * in place of a simple button in the bar. When the menu item is presented in a way that
 * does not allow custom action views, (e.g. in an overflow menu,) the ActionProvider
 * can perform a default action.</p>
 *
 * <p>There are two ways to use an action provider:
 * <ul>
 * <li>
 * Set the action provider on a {@link MenuItem} directly by calling
 * {@link MenuItem#setActionProvider(ActionProvider)}.
 * </li>
 * <li>
 * Declare the action provider in an XML menu resource. For example:
 * <pre>
 * <code>
 *   &lt;item android:id="@+id/my_menu_item"
 *     android:title="Title"
 *     android:icon="@drawable/my_menu_item_icon"
 *     android:showAsAction="ifRoom"
 *     android:actionProviderClass="foo.bar.SomeActionProvider" /&gt;
 * </code>
 * </pre>
 * </li>
 * </ul>
 * </p>
 *
 * @see MenuItem#setActionProvider(ActionProvider)
 * @see MenuItem#getActionProvider()
 */
public abstract class ActionProvider {
    private static final String TAG = "ActionProvider";
    private SubUiVisibilityListener mSubUiVisibilityListener;
    private VisibilityListener mVisibilityListener;

    
Creates a new instance. ActionProvider classes should always implement a
constructor that takes a single Context parameter for inflating from menu XML.

Params:
  • context – Context for accessing resources.
/**
     * Creates a new instance. ActionProvider classes should always implement a
     * constructor that takes a single Context parameter for inflating from menu XML.
     *
     * @param context Context for accessing resources.
     */
    public ActionProvider(Context context) {
    }

    
Factory method called by the Android framework to create new action views.

This method has been deprecated in favor of onCreateActionView(MenuItem). Newer apps that wish to support platform versions prior to API 16 should also implement this method to return a valid action view.


Returns:A new action view.
Deprecated:use onCreateActionView(MenuItem)
/**
     * Factory method called by the Android framework to create new action views.
     *
     * <p>This method has been deprecated in favor of {@link #onCreateActionView(MenuItem)}.
     * Newer apps that wish to support platform versions prior to API 16 should also
     * implement this method to return a valid action view.</p>
     *
     * @return A new action view.
     *
     * @deprecated use {@link #onCreateActionView(MenuItem)}
     */
    @Deprecated
    public abstract View onCreateActionView();

    
Factory method called by the Android framework to create new action views.
This method returns a new action view for the given MenuItem.

If your ActionProvider implementation overrides the deprecated no-argument overload onCreateActionView(), overriding this method for devices running API 16 or later is recommended but optional. The default implementation calls onCreateActionView() for compatibility with applications written for older platform versions.


Params:
  • forItem – MenuItem to create the action view for
Returns:the new action view
/**
     * Factory method called by the Android framework to create new action views.
     * This method returns a new action view for the given MenuItem.
     *
     * <p>If your ActionProvider implementation overrides the deprecated no-argument overload
     * {@link #onCreateActionView()}, overriding this method for devices running API 16 or later
     * is recommended but optional. The default implementation calls {@link #onCreateActionView()}
     * for compatibility with applications written for older platform versions.</p>
     *
     * @param forItem MenuItem to create the action view for
     * @return the new action view
     */
    public View onCreateActionView(MenuItem forItem) {
        return onCreateActionView();
    }

    
The result of this method determines whether or not isVisible() will be used by the MenuItem this ActionProvider is bound to help determine its visibility. 
See Also:
Returns:true if this ActionProvider overrides the visibility of the MenuItem
        it is bound to, false otherwise. The default implementation returns false.
/**
     * The result of this method determines whether or not {@link #isVisible()} will be used
     * by the {@link MenuItem} this ActionProvider is bound to help determine its visibility.
     *
     * @return true if this ActionProvider overrides the visibility of the MenuItem
     *         it is bound to, false otherwise. The default implementation returns false.
     * @see #isVisible()
     */
    public boolean overridesItemVisibility() {
        return false;
    }

    
If overridesItemVisibility() returns true, the return value of this method will help determine the visibility of the MenuItem this ActionProvider is bound to. 
If the MenuItem's visibility is explicitly set to false by the application,
the MenuItem will not be shown, even if this method returns true.


Returns:true if the MenuItem this ActionProvider is bound to is visible, false if
        it is invisible. The default implementation returns true.
/**
     * If {@link #overridesItemVisibility()} returns true, the return value of this method
     * will help determine the visibility of the {@link MenuItem} this ActionProvider is bound to.
     *
     * <p>If the MenuItem's visibility is explicitly set to false by the application,
     * the MenuItem will not be shown, even if this method returns true.</p>
     *
     * @return true if the MenuItem this ActionProvider is bound to is visible, false if
     *         it is invisible. The default implementation returns true.
     */
    public boolean isVisible() {
        return true;
    }

    
If this ActionProvider is associated with an item in a menu, refresh the visibility of the item based on overridesItemVisibility() and isVisible(). If overridesItemVisibility() returns false, this call will have no effect. 
/**
     * If this ActionProvider is associated with an item in a menu,
     * refresh the visibility of the item based on {@link #overridesItemVisibility()} and
     * {@link #isVisible()}. If {@link #overridesItemVisibility()} returns false, this call
     * will have no effect.
     */
    public void refreshVisibility() {
        if (mVisibilityListener != null && overridesItemVisibility()) {
            mVisibilityListener.onActionProviderVisibilityChanged(isVisible());
        }
    }

    
Performs an optional default action.


For the case of an action provider placed in a menu item not shown as an action this
method is invoked if previous callbacks for processing menu selection has handled
the event.




A menu item selection is processed in the following order:






The default implementation does not perform any action and returns false.



/**
     * Performs an optional default action.
     * <p>
     * For the case of an action provider placed in a menu item not shown as an action this
     * method is invoked if previous callbacks for processing menu selection has handled
     * the event.
     * </p>
     * <p>
     * A menu item selection is processed in the following order:
     * <ul>
     * <li>
     * Receiving a call to {@link MenuItem.OnMenuItemClickListener#onMenuItemClick
     *  MenuItem.OnMenuItemClickListener.onMenuItemClick}.
     * </li>
     * <li>
     * Receiving a call to {@link android.app.Activity#onOptionsItemSelected(MenuItem)
     *  Activity.onOptionsItemSelected(MenuItem)}
     * </li>
     * <li>
     * Receiving a call to {@link android.app.Fragment#onOptionsItemSelected(MenuItem)
     *  Fragment.onOptionsItemSelected(MenuItem)}
     * </li>
     * <li>
     * Launching the {@link android.content.Intent} set via
     * {@link MenuItem#setIntent(android.content.Intent) MenuItem.setIntent(android.content.Intent)}
     * </li>
     * <li>
     * Invoking this method.
     * </li>
     * </ul>
     * </p>
     * <p>
     * The default implementation does not perform any action and returns false.
     * </p>
     */
    public boolean onPerformDefaultAction() {
        return false;
    }

    
Determines if this ActionProvider has a submenu associated with it.

Associated submenus will be shown when an action view is not. This provider instance will receive a call to onPrepareSubMenu(SubMenu) after the call to onPerformDefaultAction() and before a submenu is displayed to the user. 
Returns:true if the item backed by this provider should have an associated submenu
/**
     * Determines if this ActionProvider has a submenu associated with it.
     *
     * <p>Associated submenus will be shown when an action view is not. This
     * provider instance will receive a call to {@link #onPrepareSubMenu(SubMenu)}
     * after the call to {@link #onPerformDefaultAction()} and before a submenu is
     * displayed to the user.
     *
     * @return true if the item backed by this provider should have an associated submenu
     */
    public boolean hasSubMenu() {
        return false;
    }

    
Called to prepare an associated submenu for the menu item backed by this ActionProvider.

if hasSubMenu() returns true, this method will be called when the menu item is selected to prepare the submenu for presentation to the user. Apps may use this to create or alter submenu content right before display. 
Params:
  • subMenu – Submenu that will be displayed
/**
     * Called to prepare an associated submenu for the menu item backed by this ActionProvider.
     *
     * <p>if {@link #hasSubMenu()} returns true, this method will be called when the
     * menu item is selected to prepare the submenu for presentation to the user. Apps
     * may use this to create or alter submenu content right before display.
     *
     * @param subMenu Submenu that will be displayed
     */
    public void onPrepareSubMenu(SubMenu subMenu) {
    }

    
Notify the system that the visibility of an action view's sub-UI such as
an anchored popup has changed. This will affect how other system
visibility notifications occur.

@hidePending future API approval
/**
     * Notify the system that the visibility of an action view's sub-UI such as
     * an anchored popup has changed. This will affect how other system
     * visibility notifications occur.
     *
     * @hide Pending future API approval
     */
    public void subUiVisibilityChanged(boolean isVisible) {
        if (mSubUiVisibilityListener != null) {
            mSubUiVisibilityListener.onSubUiVisibilityChanged(isVisible);
        }
    }

    
@hideInternal use only
/**
     * @hide Internal use only
     */
    public void setSubUiVisibilityListener(SubUiVisibilityListener listener) {
        mSubUiVisibilityListener = listener;
    }

    
Set a listener to be notified when this ActionProvider's overridden visibility changes.
This should only be used by MenuItem implementations.

Params:
  • listener – listener to set
/**
     * Set a listener to be notified when this ActionProvider's overridden visibility changes.
     * This should only be used by MenuItem implementations.
     *
     * @param listener listener to set
     */
    public void setVisibilityListener(VisibilityListener listener) {
        if (mVisibilityListener != null) {
            Log.w(TAG, "setVisibilityListener: Setting a new ActionProvider.VisibilityListener " +
                    "when one is already set. Are you reusing this " + getClass().getSimpleName() +
                    " instance while it is still in use somewhere else?");
        }
        mVisibilityListener = listener;
    }

    
@hide
/**
     * @hide
     */
    public void reset() {
        mVisibilityListener = null;
        mSubUiVisibilityListener = null;
    }

    
@hideInternal use only
/**
     * @hide Internal use only
     */
    public interface SubUiVisibilityListener {
        public void onSubUiVisibilityChanged(boolean isVisible);
    }

    
Listens to changes in visibility as reported by ActionProvider.refreshVisibility(). 
See Also:
/**
     * Listens to changes in visibility as reported by {@link ActionProvider#refreshVisibility()}.
     *
     * @see ActionProvider#overridesItemVisibility()
     * @see ActionProvider#isVisible()
     */
    public interface VisibilityListener {
        public void onActionProviderVisibilityChanged(boolean isVisible);
    }
}