Android: Make view on top of listview scroll together with the listview

Question

I have a listview which is obviously scrollable. The listview contains some form questions. Once the user submitts the form we put a stamp-like looking custom view on top of the

Answer 1

I found a solution. Not sure if it is too elegant, but it works so will leave it unless somebody comes up with something better.

The view which I want to scroll together with the list is a custom view, which has to know about the list view. So I implement a setListView(ListView listView) method on it:

private int scrollY; //1
private Map listViewItemHeights = new Hashtable<>();
public void setListView(final ListView listView) {
    listView.setOnScrollListener(new OnScrollListener() {  //2
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {} //3

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { //4
            View c = listView.getChildAt(0);
            if (c != null) {
                int oldScrollY = scrollY;
                scrollY = -c.getTop();

                listViewItemHeights.put(listView.getFirstVisiblePosition(), c.getHeight());
                for (int i = 0; i < listView.getFirstVisiblePosition(); ++i) {
                    if (listViewItemHeights.get(i) != null)
                        scrollY += listViewItemHeights.get(i);
                }
                scrollBy(0, scrollY - oldScrollY);
            }
        }
    });
}

Comment No.1: this is a variable letting me keep track of the current scroll position.

Comment No.2: setting a new on scroll listener to let my custom view know when the list

Comment No.3: this does not need to be implemented in this case.

Comment No.4: this is where magic happens. Note in the end I scroll my view by scrollY - oldScrollY, let me start with this bit first. oldScrollY is the kept scroll position, scrollY is the new one. I need to scroll by the difference between them. As for how scrollY is calculated I refer you to my answer here: Android getting exact scroll position in ListView, it is how the scroll position is calculated in list view.