Floatingactionbutton cannot be displayed as a circle normally

Use compile ' com.android.support:design:22.2.0 '

Questions to achieve Floatingactionbutton effect:

1. When it is below API17, it will be shown as a square instead of a circle, this property app:borderwidth= "0DP" to solve the problem;
2. drawable resources that cannot be known as fab_background;

This was known by Google and would be fix soon in the next version of the Design support Library, see this Issue:fab Appear S as a square on API 16. It should only concern API 16. The workaround, proposed in the same thread, are to add to app:borderWidth="0dp" your FAB.

Floatingactionbutton cannot be displayed as a circle normally