How implement sticky footer in recyclerview

Question

I have RecyclerView and I need next behavior:

• if there are a lot of items (more then fits screen) - footer is last item
• if few item/no item - footer is lo

Answer 1

Improvising on Dmitriy Korobeynikov and solving the problem of calling notify dataset changed

public class StickyFooterItemDecoration extends RecyclerView.ItemDecoration {

  @Override
  public void getItemOffsets(Rect outRect, final View view, final RecyclerView parent,
      RecyclerView.State state) {

    int position = parent.getChildAdapterPosition(view);
    int adapterItemCount = parent.getAdapter().getItemCount();
    if (adapterItemCount == RecyclerView.NO_POSITION || (adapterItemCount - 1) != position) {
      return;
    }
    outRect.top = calculateTopOffset(parent, view, adapterItemCount);
  }


  private int calculateTopOffset(RecyclerView parent, View footerView, int itemCount) {
    int topOffset =
        parent.getHeight() - parent.getPaddingTop() - parent.getPaddingBottom()
            - visibleChildHeightWithFooter(parent, footerView, itemCount);
    return topOffset < 0 ? 0 : topOffset;
  }



  private int visibleChildHeightWithFooter(RecyclerView parent, View footerView, int itemCount) {
    int totalHeight = 0;
    int onScreenItemCount = Math.min(parent.getChildCount(), itemCount);
    for (int i = 0; i < onScreenItemCount - 1; i++) {
      RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) parent.getChildAt(i)
          .getLayoutParams();
      int height =
          parent.getChildAt(i).getHeight() + layoutParams.topMargin
              + layoutParams.bottomMargin;
      totalHeight += height;
    }
    int footerHeight = footerView.getHeight();
    if (footerHeight == 0) {
      fixLayoutSize(footerView, parent);
      footerHeight = footerView.getHeight();
    }
    footerHeight = footerHeight + footerView.getPaddingBottom() + footerView.getPaddingTop();

    return totalHeight + footerHeight;
  }

  private void fixLayoutSize(View view, ViewGroup parent) {
    // Check if the view has a layout parameter and if it does not create one for it
    if (view.getLayoutParams() == null) {
      view.setLayoutParams(new ViewGroup.LayoutParams(
          ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
    }

    // Create a width and height spec using the parent as an example:
    // For width we make sure that the item matches exactly what it measures from the parent.
    //  IE if layout says to match_parent it will be exactly parent.getWidth()
    int widthSpec = View.MeasureSpec.makeMeasureSpec(parent.getWidth(), View.MeasureSpec.EXACTLY);
    // For the height we are going to create a spec that says it doesn't really care what is calculated,
    //  even if its larger than the screen
    int heightSpec = View.MeasureSpec
        .makeMeasureSpec(parent.getHeight(), View.MeasureSpec.UNSPECIFIED);

    // Get the child specs using the parent spec and the padding the parent has
    int childWidth = ViewGroup.getChildMeasureSpec(widthSpec,
        parent.getPaddingLeft() + parent.getPaddingRight(), view.getLayoutParams().width);
    int childHeight = ViewGroup.getChildMeasureSpec(heightSpec,
        parent.getPaddingTop() + parent.getPaddingBottom(), view.getLayoutParams().height);

    // Finally we measure the sizes with the actual view which does margin and padding changes to the sizes calculated
    view.measure(childWidth, childHeight);

    // And now we setup the layout for the view to ensure it has the correct sizes.
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
  }
}