Difference Between AppBar, ActionBar, and Toolbar in Android

AppBar, ActionBar, and Toolbar are components in Android that help in providing navigation and action UI patterns. While they may seem similar or related, they have distinct roles and characteristics:

AppBar:
- Definition: The AppBar is a more general term referring to the application bar UI pattern in Material Design. It typically consists of a horizontal bar at the top of the UI which can contain branding, navigation, actions, and other elements.
- Components: The AppBar can consist of a combination of UI elements. Typically, it's made up of a Toolbar and may also include a TabLayout for navigation between app sections.
- Usage Context: It's often associated with Material Design, and it's the recommended approach to provide a consistent app-wide navigation and action paradigm.
ActionBar:
- Definition: Introduced in Android 3.0 (Honeycomb), the ActionBar is the original system component for providing a top app bar. It supports a set of specific functionalities like app branding, navigation modes (like tabs and dropdown lists), and action buttons.
- Customization: Its functionality and appearance are a bit more rigid compared to the Toolbar. While you can customize it to some extent, its flexibility is limited.
- Usage Context: The ActionBar was the default component for navigation and actions before Material Design was introduced. While it can still be used today, the Toolbar (and generally the AppBar pattern) is preferred due to its greater flexibility and modern design.
Toolbar:
- Definition: Introduced with Android 5.0 (Lollipop) and Material Design, the Toolbar is a more flexible and powerful UI component that can act as a replacement for the ActionBar or can be used in other parts of the app UI.
- Flexibility: The Toolbar is essentially a generalized action bar. Being a ViewGroup, it can be placed anywhere in your layout, not just at the top. You can have multiple Toolbar components in an activity, and it can contain custom views.
- Integration: To use a Toolbar as a replacement for the default ActionBar, you need to specify this in your app's theme and then use setSupportActionBar(toolbarInstance) in your activity.
- Usage Context: With the advent of Material Design, the Toolbar is the recommended way to implement the top app bar pattern. It's a component that's part of the AppBar but is more versatile, as it can be used outside the typical top bar context as well.

In summary:

AppBar is a broader term related to the application bar UI pattern in Material Design and might consist of a Toolbar, TabLayout, and other components.
ActionBar is the original system component for a top app bar, providing navigation and action items. While still usable, it's largely superseded by the Toolbar.
Toolbar is a modern, flexible component that can replace the ActionBar or be used in other contexts. It's often a primary component within the AppBar in Material Design apps.