invalidateOptionsMenu() is used to say Android, that contents of menu have changed, and menu should be redrawn. For example, you click a button which adds another menu item at runtime, or hides menu items group. In this case you should call invalidateOptionsMenu() , so that the system could redraw it on UI.
What is the role of return true or false from the callback method onCreateOptionsMenu?
Returns boolean You must return true for the menu to be displayed; if you return false it will not be shown.
Which is valid menu in Android?
For all menu types, Android provides a standard XML format to define menu items. Instead of building a menu in your activity’s code, you should define a menu and all its items in an XML menu resource. You can then inflate the menu resource (load it as a Menu object) in your activity or fragment.
What is the use of Menuinflater in Android?
This class is used to instantiate menu XML files into Menu objects. For performance reasons, menu inflation relies heavily on pre-processing of XML files that is done at build time.
What are the two types of popup menu?
Usage
- Contextual Action Modes – An “action mode” which is enabled when a user selects an item. …
- PopupMenu – A modal menu that is anchored to a particular view within an activity. …
- PopupWindow – A simple dialog box that gains focus when appearing on screen.
What is ActionBar?
In Android applications, ActionBar is the element present at the top of the activity screen. It is a salient feature of a mobile application that has a consistent presence over all its activities. It provides a visual structure to the app and contains some of the frequently used elements for the users.
What is ifRoom in android?
Description. ifRoom. Only place this item in the app bar if there is room for it. If there is not room for all the items marked “ifRoom” , the items with the lowest orderInCategory values are displayed as actions, and the remaining items are displayed in the overflow menu.
What are activities in android?
You implement an activity as a subclass of the Activity class. An activity provides the window in which the app draws its UI. … Generally, one activity implements one screen in an app. For instance, one of an app’s activities may implement a Preferences screen, while another activity implements a Select Photo screen.
What is the best definition of an action in Android?
In Google’s definition, an Action is: “An interaction you build for the Assistant that supports a specific intent and has a corresponding fulfillment that processes the intent”.
When should we use FrameLayout?
FrameLayout is designed to block out an area on the screen to display a single item. Generally, FrameLayout should be used to hold a single child view, because it can be difficult to organize child views in a way that’s scalable to different screen sizes without the children overlapping each other.
How do I use pop up menu on Android?
Android Popup Menu displays the menu below the anchor text if space is available otherwise above the anchor text.
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Android Popup Menu Example
- <? …
- android:layout_width=”match_parent”
- android:layout_height=”match_parent”
- tools:context=”example.javatpoint.com.popupmenu.MainActivity”>
- <Button.