app/src/main/res/drawable/dropdown.xml

<vector android:height="24dp" android:tint="#FFFFFF"
    android:viewportHeight="24" android:viewportWidth="24"
    android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">

    <path
        android:fillColor="@android:color/white"
        android:pathData="M7.41,8.59L12,13.17l4.59,
        -4.58L18,10l-6,6 -6,-6 1.41,-1.41z"/>

</vector>