clipToOutline with cornerRadii with background

Question

Sometimes in my practice I want to round view's background corners. Usually i use something like this (@drawable/bg_rounded)

<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <corners android:radius="16dp"/>
</shape>

But sometimes i need to round only one angle and do this programmatically

I create a test project to show the problem. activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:layout_margin="20dp"
    android:background="@drawable/bg_rounded">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/purple_200"/>

</FrameLayout>

MainActivity class may be like

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val container = findViewById<FrameLayout>(R.id.container)
        container.clipToOutline = true
        val background: GradientDrawable =
            container.background.mutate() as? GradientDrawable ?: return
        background.cornerRadii = floatArrayOf(
            20F, 20F, 20F, 20F,
            20F, 20F, 20F, 20F
        )
    }
}

but unexpected behavior happens - corners are not rounded click to see picture

if i use background.cornerRadius it works predictable

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val container = findViewById<FrameLayout>(R.id.container)
        container.clipToOutline = true
        val background: GradientDrawable =
            container.background.mutate() as? GradientDrawable ?: return
        background.cornerRadius = 20F
//        background.cornerRadii = floatArrayOf(
//            20F, 20F, 20F, 20F,
//            20F, 20F, 20F, 20F
//        )
    }
}

click to see picture

So my question is: what should I use to achieve dynamic adjustment of different radius of corners