Should we replace Action Bar by ToolBar?

Question

I have been using ToolBar since it was added into Support v7 library. And I think I used it well. But there is a point I can\'t understand. Why

Answer 1

why Android would create such a widget?

Imagine, if you will, an Android tablet.

This tablet is running an app. That app has, in the lower-right corner of the screen, a rich text editor, where one can enter in some comments and format them with bold, italic, etc.

In a desktop or Web app, a typical approach for those formatting options, besides keyboard shortcuts, would be a toolbar, like the one you see above the answer text area here on Stack Overflow.

Prior to Toolbar, Android developers had to either roll their own toolbar, or put the formatting actions in the action bar. While the latter approach is easy, it puts a strain on the user of the aforementioned fictional app, as the user has to keep switching her visual focus from the editor (bottom of screen) to the action bar (top of screen).

Why have we to use ToolBar?

You do not have to use Toolbar. I have ~300 sample apps as part of my book, and at the moment, precisely zero of them use Toolbar. I'll have to correct that at some point, as I have not yet written a chapter on Toolbar.

Is it necessary to replace ActionBar by ToolBar?

No. There is a way to do this, but it is not necessary.