Why are API demos considered “legacy” like API 18?

Question

After installing the latest Android ADTs and SDKs to support API 18, I noticed that all API demos are now considered "deprecated."

Here is a screenshot:

How did it happen?

I noticed that although they are considered a “legacy”, they contain some things that belong to API 18, for example, this attribute found in the manifest:

android:theme="@android:style/Theme.Holo.NoActionBar.Overscan" 

It's also weird that this is the only thing Lint warns me that minSdk will be below API 18 - this may not be the only new thing in API 18 that the demos contain, is it?

What happens with this and we will have a different set of samples?

Answer 1

Uninvited projects have a build.gradle file that you can simply open in Android Studio *. Obsolete projects do not have a build.gradle file, and if you want to open them in Android Studio, you need to either go through “create a new project on top of existing sources” or android update project before you can continue.

*) Not quite right: some of them point to outdated versions of the Android plugin, and you need to configure the project settings first.