右三角形

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <rotate
            android:fromDegrees="45"
            android:pivotX="15%"
            android:pivotY="-35%">
            <shape android:shape="rectangle">
                <size
                    android:width="9dp"
                    android:height="9dp" />
                <solid android:color="#CC000000" />
            </shape>
        </rotate>
    </item>
</layer-list>