ActionProvider

abstract class ActionProvider

This class is a mediator for accomplishing a given task, for example sharing a file. It is responsible for creating a view that performs an action that accomplishes the task. This class also implements other functions such a performing a default action.

An ActionProvider can be optionally specified for a android.view.MenuItem and in such a case it will be responsible for creating the action view that appears in the android.app.ActionBar as a substitute for the menu item when the item is displayed as an action item. Also the provider is responsible for performing a default action if a menu item placed on the overflow menu of the ActionBar is selected and none of the menu item callbacks has handled the selection. For this case the provider can also optionally provide a sub-menu for accomplishing the task at hand.

There are two ways for using an action provider for creating and handling of action views:

• Setting the action provider on a android.view.MenuItem directly by calling setActionProvider.
• Declaring the action provider in the menu XML resource. For example:

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

To create a custom action provider, extend ActionProvider and implement its callback methods as necessary. In particular, implement the following methods:

ActionProvider() constructor

This constructor is passed the application context. You should save the context in a member field to use in the other callback methods.

onCreateActionView(MenuItem)

The system calls this method when the action provider is created. You define the action provider's layout through the implementation of this method. Use the context acquired from the constructor to instantiate a android.view.LayoutInflater and inflate your action provider's layout from an XML resource, then hook up event listeners for the view's components. For example:

public View onCreateActionView(MenuItem forItem) {
    // Inflate the action provider to be shown on the action bar.
    LayoutInflater layoutInflater = LayoutInflater.from(mContext);
    View providerView =
        layoutInflater.inflate(R.layout.my_action_provider, null);
    ImageButton button =
        (ImageButton) providerView.findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // Do something...
        }
    });
    return providerView;
}

onPerformDefaultAction()

The system calls this method when the user selects a menu item from the action overflow. The action provider should perform a default action for the menu item. The system does not call this method if the menu item opens a submenu.

If your action provider presents a submenu through the onPrepareSubMenu() callback, the submenu appears even if the action provider is in the overflow menu. Thus, the system never calls onPerformDefaultAction() if there is a submenu.

Note: An activity or a fragment that implements onOptionsItemSelected() can override the action provider's default behavior (unless it uses a submenu) by handling the item-selected event and returning true. In this case, the system does not call onPerformDefaultAction().

Summary

ActionProvider(context: Context)

fun getContext(): Context

fun hasSubMenu(): Boolean

fun isVisible(): Boolean

abstract fun onCreateActionView(): View

fun onCreateActionView(forItem: MenuItem): View

fun onPerformDefaultAction(): Boolean

fun onPrepareSubMenu(subMenu: SubMenu): Unit

fun overridesItemVisibility(): Boolean

fun refreshVisibility(): Unit

fun setVisibilityListener(listener: ActionProvider.VisibilityListener?): Unit