Android: onScrollStateChanged SCROLL_STATE_IDLE sometimes doesn't fire

Question

I\'m running into a bit of a problem. What I\'m doing: I\'ve got a ListView which has got some images in it. To make the scrolling smoother I\'ve disabled the images to show up

Answer 1

I ran into the same issue with a RecyclerView.

Jason Burke's answer is correct, but I'll provide an alternate way of checking if you are at the beginning/end of the RecyclerView/ListView.

I do it in onScrolled instead of onScrollStateChanged since I don't trust that I get a state changed event in the case when you scroll/fling to the edge of the RecyclerView.

recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {

    override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
        super.onScrollStateChanged(recyclerView, newState)

        if (newState == RecyclerView.SCROLL_STATE_IDLE) {
            updateUi()
        }
    }

    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
        super.onScrolled(recyclerView, dx, dy)

        /* If the user scrolls to the edges of the recyclerview, we can't trust that we get the SCROLL_STATE_IDLE state.
         * Therefore we have to update the view here in onScrolled for these cases
         */
        if (!recyclerView.canScrollVertically(1) || !recyclerView.canScrollVertically(-1)) {
            updateUi()
        }
    }
}

In my case it was actually a horizontal RecyclerView, so I had to do this instead:

if (!recyclerView.canScrollHorizontally(1) || !recyclerView.canScrollHorizontally(-1)) {
    updateUi()
}