# App Bars  `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 * [Material Design guidelines: App Bars](https://material.io/guidelines/layout/structure.html#structure-app-bar) * [Material Design guidelines: Scrolling techniques](https://material.io/guidelines/patterns/scrolling-techniques.html) * [Class definition](https://github.com/material-components/material-components-android/tree/master/lib/src/android/support/design/widget/AppBarLayout.java) * [Class overview](https://developer.android.com/reference/android/support/design/widget/AppBarLayout.html) As a container for Toolbars, and other views, it works with [CoordinatorLayout](CoordinatorLayout.md) 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](https://developer.android.com/reference/android/support/v4/widget/NestedScrollView.html), [RecyclerView](https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html)). 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](https://developer.android.com/reference/android/support/design/widget/AppBarLayout.LayoutParams.html#SCROLL_FLAG_ENTER_ALWAYS) * [enterAlwaysCollapsed](https://developer.android.com/reference/android/support/design/widget/AppBarLayout.LayoutParams.html#SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED) * [exitUntilCollapsed](https://developer.android.com/reference/android/support/design/widget/AppBarLayout.LayoutParams.html#SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) * [scroll](https://developer.android.com/reference/android/support/design/widget/AppBarLayout.LayoutParams.html#SCROLL_FLAG_SCROLL) * [snap](https://developer.android.com/reference/android/support/design/widget/AppBarLayout.LayoutParams.html#SCROLL_FLAG_SNAP) 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 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](https://developer.android.com/reference/android/support/v7/app/AppCompatActivity.html#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. * [App bar](https://material.io/guidelines/layout/structure.html#structure-app-bar) * [Toolbars](https://material.io/guidelines/components/toolbars.html#toolbars-usage) * [CollapsingToolbarLayout](CollapsingToolbarLayout.md)