Make FAB not to be clipped inside bottom navigation bar

Your problem is that you have explicitly specified width and heigh parameters of FloatingActionButton, whereas it cannot take any width/height. app:fabSize parameters specifies 3 sizes for the fab: auto, mini, and normal.

Leave layout_width and layout_height as wrap_content, and specify the desired fab size using app:fabSize="normal" (or other parameter from the list).

Additionally, make BottomNavigationView's height wrap_content, because fab has some internal paddings.

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In order to draw a child outside of the enclosing layout apply android:clipChildren="false" to the enclosing ViewGroup.