Is there any distinction between the key functionality of Android controls: Action bar vs. Toolbar, Spinner vs. Dropdown. To me they seem to be the same and I wonder if there is a reason of introducing new terminology for the controls that already existed.
Spinners and Pickers are effectively attractive drop-down lists, but they both have a slightly different form.
A spinner is more streamlined, and can be found within the action bar to quickly change data sets or views(email account, calendar view, etc).
A picker takes up more space, and is more like an analog radio dial, in my mind. It's great for step-wise data like Times, Dates, or other gradually increasing/decreasing numbers.
I do admit to being a little confused about the names, since you pick from a spinner and spin a picker, but I try not to ponder that too much.
I'm not sure if anything in Android is called a toolbar, but the action bar tends to serve this purpose in most apps. The main functions sit on the action bar, with the rest overflowing when needed. The action bar can change its buttons depending on context, which makes it behave like a toolbar that only shows up when you need it. For instance, when you select an email, you get options to Archive, Delete, Label, Mark as unread, Star, etc.
@Karen covers the Spinner vs Picker question. Regarding the ActionBar vs Toolbar question:
That brings us to the Material design that was released with Android v5.0 (Lollipop). Due to the increasingly robust uses they wanted the
The benefit is that this new
Nowadays, everyone uses the
In fact, the Material design guidelines pretty much require this since the Toolbar is required to interact with scrolling content and other features that the
For further reading, see the Android Toolbar developer documentation