Doesn't Show Icon in the Layout on Marshmallow

[sagaratalatti]

trafficstars

I have tried using this code for layout but the icon doesn't show! minSdkVersion is 17 and targetSdkVersion is 25

<com.sackcentury.shinebuttonlib.ShineButton
                android:layout_width="50dp"
                android:layout_height="50dp"
                android:layout_centerInParent="true"
                android:src="@android:color/darker_gray"
                android:id="@+id/po_image1"
                app:btn_color="@android:color/darker_gray"
                app:btn_fill_color="#FF6666"
                app:allow_random_color="false"
                app:enable_flashing="false"
                app:big_shine_color="#FF6666"
                app:click_animation_duration="200"
                app:shine_animation_duration="1500"
                app:shine_turn_angle="10"
                app:small_shine_offset_angle="20"
                app:shine_distance_multiple="1.5f"
                app:small_shine_color="#CC9999"
                app:shine_count="8"
                app:siShape="@raw/heart"/>

[ChadCSong]

Suggest you use new release version 0.1.9. Thanks.