RecyclerView scrollToPosition not trigger scrollLi

Question

I'm using RecyclerView, with ScrollListener:

mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener()
{
        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState)
        {
            super.onScrollStateChanged(recyclerView, newState);
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy)
        {
            super.onScrolled(recyclerView, dx, dy);
            // Do my logic
        }
 });

When I scroll with the finger, the scroll listener triggered fine.

But when I scroll progrematically, like that:

mRecyclerView.scrollToPosition(LAST_POSITION);

The scroll listener is not triggered.

Answer 1

int mFirst=0, mLast=0;

recyclerview.setOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
    }
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        LinearLayoutManager llm = (LinearLayoutManager) recyclerview.getLayoutManager();
        mLast = llm.findLastCompletelyVisibleItemPosition();
        mFirst = llm.findFirstCompletelyVisibleItemPosition();
    }
});

imgRight.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        LinearLayoutManager llm = (LinearLayoutManager) recyclerview.getLayoutManager();
        llm.scrollToPositionWithOffset(mLast + 1, List.length());
    }
});

imgLeft.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        LinearLayoutManager llm = (LinearLayoutManager) recyclerview.getLayoutManager();
        llm.scrollToPositionWithOffset(mFirst - 1, List.length());
    }
});

Answer 2

Please try with

LinearLayoutManager.scrollToPositionWithOffset(int, int).

LayoutManager.scrollToPosition() may not work well, but LinearLayoutManager.scrollToPositionWithOffset() will work. And similarlly GridLayoutManager as well.

Or we have to write our custom way of implementation because RecyclerView doesn't know how LayoutManager scrolls the view.

    class CustomLayoutManager extends LinearLayoutManager{
         public void smoothScrollToPosition(RecyclerView recyclerView,
                RecyclerView.State state, final int position) {

          LinearSmoothScroller smoothScroller = 
                    new LinearSmoothScroller(mContext) {
        //Override the methods and write your implementation as per your requirement 
       //one which controls the direction and another one calculate the speed per Pixel
        }
    }

Sometimes this does the trick

    new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {
        yourList.scrollToPosition(position);
    }
}, 200);