I just started programming using Android Studio and it's so cute. But at first compile some errors occurred.
I added a Login Activity and found out that this activity does not support programming for older phones with API9.
Is there an Android Studio activities for lower version APIs such as API9 (Android 2.3.3) ?
The way to support earlier API versions is through the official Android Support libraries. Mostly these are backported versions of more recent features added in later API levels.
See http://developer.android.com/tools/support-library/index.html for more details.
If you create a new project using the Android Studio wizard and set the minimum SDK level to 9 for example, it will automatically include support library dependencies for you.