Difference Between ActionBar and Toolbar in Android

Both the ActionBar and Toolbar in Android serve the primary purpose of providing a UI component at the top of the screen that can represent navigation, actions, and app branding. However, they differ in terms of flexibility, customization, and the era of Android design in which they were predominant. Here's a comparison:

Historical Context:
- ActionBar: Introduced in Android 3.0 (Honeycomb), the ActionBar was the default solution for a long time to show the app title, navigation, and other actions.
- Toolbar: With the advent of Material Design in Android 5.0 (Lollipop), Google introduced the Toolbar as a more flexible and versatile replacement for the ActionBar.
Flexibility:
- ActionBar: Its functionality and appearance are more rigid and follow specific guidelines. While some customization is possible, it's limited compared to the Toolbar.
- Toolbar: Essentially, it's a generalized action bar. It's part of the AndroidX library, making it backward-compatible with older Android versions. Being just a ViewGroup, it can be placed anywhere in your layout and provides more flexibility in terms of customization and appearance. You can have more than one Toolbar in an activity or fragment, which wasn't a typical use-case for ActionBar.
Customization:
- ActionBar: It supports a set of specific features, such as tabs, dropdown lists, and navigation modes, but customization can be a bit cumbersome.
- Toolbar: Since it's a ViewGroup, it can contain any custom widget or view. This makes branding, styling, and adding custom views a breeze compared to the ActionBar.
Implementation:
- ActionBar: It's provided by the system, and every activity has one by default (unless you use a theme that explicitly says otherwise, like NoActionBar).
- Toolbar: You need to add it to your XML layout manually, and if you want to replace the default ActionBar with a Toolbar, you'll have to call setSupportActionBar(toolbarInstance).
Integration with Navigation Components:
- ActionBar: Using the ActionBar with Android's modern navigation components (like the Navigation Architecture Component) can be less straightforward.
- Toolbar: Being the more modern solution, it integrates more seamlessly with Android's latest navigation components, making it easier to set up with the Navigation Architecture Component, for instance.
Usage Context:
- ActionBar: It was more predominant in the Holo design era, and its usage has declined over time in favor of the more flexible Toolbar.
- Toolbar: With the Material Design era, the Toolbar has become the go-to solution for top-level navigation and action displays in Android apps.

In summary, while both the ActionBar and Toolbar can serve similar purposes, the Toolbar offers more flexibility and customization options. If you're starting a new project or updating an old one, it's generally recommended to use the Toolbar because of its adaptability and the modern design practices it adheres to.