change the background and the image from wtihin a spinner

spinnerlayerlist.java

ANDROID
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<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:top="8dp" android:bottom="8dp">
        <shape>
            <solid android:color="@android:color/white" />
            <stroke
                android:width="0.1dp"
                android:color="@color/color_primary" />
            <padding
                android:top="16dp"
                android:bottom="16dp"
                android:left="8dp"
                android:right="16dp"/>
        </shape>
    </item>

    <item>
        <bitmap android:gravity="center|right"
            android:src="@drawable/drop_down_red_arrow"/>
    </item>
</layer-list>

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apply it ina background attribute