AppBarLayout.md

Top App Bars

AppBarLayout is a ViewGroup, most commonly used to wrap a Toolbar, that provides many of the Material Design features and interactions for Top App Bars, namely responsiveness to scrolling.

Design & API Documentation

• Material Design guidelines: Top App Bar
• Material Design guidelines: Scrolling techniques
• Class definition
• Class overview

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 AppBarLayout.LayoutParams.

Available flags are:

• enterAlways
• enterAlwaysCollapsed
• exitUntilCollapsed
• scroll
• snap
• snapMargins

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.

Related Concepts

The Top 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 Top App Bar. They are programmatically identical and use the Toolbar class.

The Top 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 Top App Bar.

A CollapsingToolbarLayout is often used as a wrapper around the Toolbar to provide additional UI features in relation to scrolling.

• Top App Bar
• CollapsingToolbarLayout