问Android:形状绘图中填充的用途是什么？

EN

<ripple xmlns:android="http://schemas.android.com/apk/res/android"
        android:color="?attr/colorControlHighlight">
    <item android:drawable="@drawable/btn_default_mtrl_shape" />
</ripple>

<?xml version="1.0" encoding="utf-8"?>
<inset xmlns:android="http://schemas.android.com/apk/res/android"
       android:insetLeft="@dimen/button_inset_horizontal_material"
       android:insetTop="@dimen/button_inset_vertical_material"
       android:insetRight="@dimen/button_inset_horizontal_material"
       android:insetBottom="@dimen/button_inset_vertical_material">
    <ripple android:color="?attr/colorControlHighlight">
        <item>
            <shape android:shape="rectangle"
                   android:tint="@color/btn_colored_background_material">
                <corners android:radius="@dimen/control_corner_material" />
                <solid android:color="@color/white" />
                <padding android:left="@dimen/button_padding_horizontal_material"
                         android:top="@dimen/button_padding_vertical_material"
                         android:right="@dimen/button_padding_horizontal_material"
                         android:bottom="@dimen/button_padding_vertical_material" />
            </shape>
        </item>
    </ripple>

</inset>