The support repository we downloaded in the last chapter provides code that allows us to apply our designs on handsets going all the way back to Android 1.8, although the further back you go, the fewer features are supported. For the purpose of this book, we will make our applications backwards compatible as far back as API 16.
To achieve this, we will be using code provided by the AppCompat support library; in doing so, we will encounter one of the most significant material components: the Toolbar, which replaced the previous, less flexible Action Bar.
In older versions of Android, unless switched off, the Action Bar would sit at the top of each app and could contain our title along with any of the option menu items we chose, which were expressed as text, icons, or both. It was not really considered a true part of the UI, but rather an element that sat outside our design.
The new toolbar, although often acting as our app's action bar, is far more flexible...