How to add shadow to the FAB provided with the android support design library?

Simply setting app:borderWidth="0dp" resolve this issues for me.

Note: don't forget to add xmlns:app="http://schemas.android.com/apk/res-auto" to your root layout.

This issue should be fixed in next release of android design library.

For API 21+ you need to set app:borderWidth="0dp" and app:elevation="[number]dp". Setting elevation you are giving the size of shadow that you want:

Here is an example of code for API 21+:

<android.support.design.widget.FloatingActionButton
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/locate_user_FAB"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/location_off"
    app:elevation="6dp"
    app:borderWidth="0dp"
    android:layout_above="@+id/take_taxi_FAB"
    app:backgroundTint="@color/colorAccentGrey">

One important thing to remember for APIs below to 21 (Android 4), is for terms of compatibility FAB will put a margins around your button to draw the shadow. Then you should do something like that (I'm currently using this code and works):

<android.support.design.widget.FloatingActionButton
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/locate_user_FAB"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/location_off"
    app:elevation="6dp"
    app:borderWidth="0dp"
    android:layout_above="@+id/take_taxi_FAB"
    android:layout_alignParentRight="true"
    android:layout_marginRight="@dimen/map_FAB_marginRight"
    android:layout_marginBottom="@dimen/locate_user_FAB_marginBottom"
    app:backgroundTint="@color/colorAccentGrey">

I prefer to put xmlns:app="http://schemas.android.com/apk/res-auto" at the beginning of the XML, but I put there just to remind you ;]

I was experiencing this same issue and I got it to work by deleting this tag from my AndroidManifest.xml.

android:hardwareAccelerated="false"

I initially added it, together with android:largeHeap="true", because I thought I needed it for a HeatMap in which a large number of points where shown, but then I realized it could work just with android:largeHeap="true".