Expand appbarlayout when recyclerview is scrolled/fling to top

Question

I implemented a collapsingtoolbar layout with a recyclerview as shown in the sample code attached. My issue is that, when I fling the list downward, it does not go all the way to the top.

What happens is that, the scrolling stops right at the point where the AppBarLayout is supposed to end.

The effect that I want is upon flinging the list downward, the list will go all the way to the top AND reveal/expand the AppBarLayout

My minSdk is 14. Any help or suggestion is greatly appreciated.

<?xml version="1.0" encoding="utf-8"?>

<android.support.design.widget.AppBarLayout>

    <android.support.design.widget.CollapsingToolbarLayout
        app:layout_scrollFlags="scroll|exitUntilCollapsed">

        <LinearLayout
            app:layout_collapseMode="parallax">

            //some elements

        </LinearLayout>

    </android.support.design.widget.CollapsingToolbarLayout>

</android.support.design.widget.AppBarLayout>

<android.support.v7.widget.RecyclerView
    app:layout_behavior="@string/appbar_scrolling_view_behavior"/> //value android.support.design.widget.AppBarLayout$ScrollingViewBehavior

<android.support.v7.widget.Toolbar
    app:popupTheme="@style/AppTheme.PopupOverlay"
    app:layout_collapseMode="parallax" />

Answer 1

I had similar problem and I used a simple trick to expand AppBarLayout when RecyclerView fling to top (you need to have support library >= 23.x.x)

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    int firstVisiblePosition = linearLayoutManager.findFirstCompletelyVisibleItemPosition();
                    if (firstVisiblePosition == 0) {
                        mAppBarLayout.setExpanded(true, true);
                    }
                }
            }
});