AppBarLayout is the ViewGroup used to wrap the app bar that provides many of the Material Design features and interactions for app bars, namely responsiveness to scrolling.
Design & API Documentation
As a container for Toolbars, and other views, it works with CoordinatorLayout in order to respond to scrolling techniques.
AppBarLayout depends heavily on being used as a direct child of the CoordinatorLayout and reacts to a sibling that supports scrolling (e.g. NestedScrollView, RecyclerView).
Flags are added to each child of the
AppBarLayout to control how they will respond to scrolling. These are interpreted by the
Available flags are:
Views using the scroll flag should be declared and visually positioned before other views in the
AppBarLayout. This ensures that they are able to exit at the top of the screen, leaving behind fixed, or pinned, elements.
The app bar is a way of referencing a specific type of Toolbar. It’s not a separate Android class. This UI element is often used to provide branding for the app as well as a place to handle common actions like navigation, search, and menus. These are accessible via text or buttons in the Toolbar. A Toolbar that provides some of these features is often referred to as the app bar. They are programatically identical and use the Toolbar class.
The app bar was previously termed action bar, and there are methods that utilize this name (e.g. getSupportActionBar). Other than use of the action bar APIs, references to this prominent Toolbar element should be app bar.
A CollapsingToolbarLayout is often used as a wrapper around the Toolbar to provide additional UI features in relation to scrolling.