ScrollBarStyle didn't show in apps

Question

i tried make a custom scrollbar style, but it show nothing when the app is running, here is my style

<style name="scrollbar_shape_style">
        <item name="android:scrollbarAlwaysDrawVerticalTrack">true</item>
        <item name="android:scrollbarStyle">outsideOverlay</item>
        <item name="android:scrollbars">vertical</item>
        <item name="android:fadeScrollbars">true</item>
        <item name="android:scrollbarThumbVertical">@drawable/scrollbar_vertical_thumb</item>
        <item name="android:scrollbarSize">8dp</item>
        <item name="android:fadeDuration">2000</item>
        <item name="android:scrollbarDefaultDelayBeforeFade">1000</item>
</style>

this is my drawable code :

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

    <gradient
        android:startColor="@color/dc_blue"
        android:endColor="@color/facebook_blue"
        android:angle="45"/>

    <corners
        android:radius="6dp"/>

</shape>

and this is my RecyclerView

<com.srx.widget.PullToLoadView
        android:id="@+id/pullToLoadView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/dc_grey_background"
        android:layout_above="@+id/menu_bar"
        style="@style/scrollbar_shape_style"/>

i think i use library for recyclerview, thank you in advance