ViewGroup.childrenByType.kt

inline fun <reified T : View> ViewGroup.childrenByType(): Sequence<T> = descendantsBreadth.filterIsInstance<T>()

val ViewGroup.descendantsBreadth: Sequence<View>
    get() = sequence {
        val queue: Queue<View> = LinkedList()
        this@descendantsBreadth.forEach { child -> queue.offer(child) }

        var child = queue.poll()
        while (child != null) {
            yield(child)
            if (child is ViewGroup) {
                for (i in 0 until child.childCount) {
                    queue.offer(child.getChildAt(i))
                }
            }

            child = queue.poll()
        }
    }