如果RecyclerView太短，则Android LinearLayoutManager scrollToPositionWithOffset无法正常工作

Question

Problem description

LinearLayoutManager.scrollToPositionWithOffset(pos, 0) works great if the sum of RecyclerView 's all children's height is big than screen height. But it does not work if the sum of RecyclerView 's all children's height is small than screen height.

Problem description in detail

Let's say I have an Activity and a RecyclerView as it's root view. RecyclerView 's width and height are both match_parent . This RecyclerView has 3 items and the sum of these 3 child view's height is small than screen height. I want to hide first item when Activity is onCreated . User will see second item at start. If user scroll down, he still can see first item. So I call LinearLayoutManager.scrollToPositionWithOffset(1, 0) . But it won't work since the sum of RecyclerView 's all children's height is small than screen height.

Question

How can I make RecyclerView scroll to specific position even though the sum of RecyclerView 's all children's height is small than screen height.

---

Following is my code according to @Haran Sivaram's answer:

Item first = new Item();
Item second = new Item();
Item third = new Item();
List<Item> list = Arrays.asList(first, second, three);

adapter.add(list);
adapter.notifyDataSetChanged();

recyclerView.post(new Runnable() {
            @Override
            public void run() {
                int sumHeight = 0;
                for (int i = 0; i < recyclerView.getChildCount(); i++) {
                    View view = recyclerView.getChildAt(i);
                    sumHeight += view.getHeight();
                }
                if (sumHeight < recyclerView.getHeight()) {
                    adapter.addItem(new VerticalSpaceViewModel(recyclerView.getHeight() - sumHeight + recyclerView.getChildAt(0).getHeight()));
                }
                linearLayoutManager.scrollToPositionWithOffset(1, 0);
            }
        });

It worked. But has some small issues.

Answer 1

What you need to do is to increase the height of the recycler view to a minimum height which will allow scrolling and hide your first element (screen height + height of the first item) . You can achieve this by adding a dummy element as the last element and setting it's height or you could also do this using padding/margins (Have not tried this).

This also needs to be done dynamically once the view is drawn (You can do it statically if you are aware of the sizes of each item beforehand - I will not recommend this method though).

Use an onGLobalLayoutListner to get a callback once the view is drawn, do your measurements here and update the height. Now the scroll with offset should work fine.