CODEWITHSUNDEEP
javaandroidkotlin
Nicola
Nicola

Reputation: 331

Android smoothScrollToPosition doesn't work properly

I'm using this function to scroll to the selected position inside the horizontal recyclerview. The problem is that if I scroll the recycler and then click an item, it doesn't go to the center of the view. Instead, if I doesn't scroll the recycler, it works. I'm using this method when I click on an item. The position is the adapterPosition.

override fun scrollToSelected(position: Int, isLeftScroll: Boolean) {
if(!isLeftScroll || position == 0) contactRV.layoutManager?.smoothScrollToPosition(contactRV, RecyclerView.State(), position +1)
    else contactRV.layoutManager?.smoothScrollToPosition(contactRV, RecyclerView.State(), position-1)

What should I do to solve this problem?

Upvotes: 0

Views: 701

Answers (1)

VIISHRUT MAVANII
VIISHRUT MAVANII

Reputation: 12708

You will Achieve by implementing RecyclerView.SmoothScroller's method onTargetFound(View, State, Action).

/**
 * Called when the target position is laid out. This is the last callback SmoothScroller
 * will receive and it should update the provided {@link Action} to define the scroll
 * details towards the target view.
 * @param targetView    The view element which render the target position.
 * @param state         Transient state of RecyclerView
 * @param action        Action instance that you should update to define final scroll action
 *                      towards the targetView
 */
abstract protected void onTargetFound(View targetView, State state, Action action);

Specifically in LinearLayoutManager with LinearSmoothScroller:

public class CenterLayoutManager extends LinearLayoutManager {

    public CenterLayoutManager(Context context) {
        super(context);
    }

    public CenterLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    public CenterLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        RecyclerView.SmoothScroller smoothScroller = new CenterSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private static class CenterSmoothScroller extends LinearSmoothScroller {

        CenterSmoothScroller(Context context) {
            super(context);
        }

        @Override
        public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) {
            return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
        }
    }
}

Upvotes: 2

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