How can I control the scrolling speed of recyclerView.smoothScrollToPosition(position)?

I have a recycler view, and I want a smooth scrolldown and then scrollup to it programatically to show the complete content in it to user.

I can do this by:

    final int height=recyclerView.getChildAt(0).getHeight();
    recyclerView.smoothScrollToPosition(height);
    recyclerView.postDelayed(new Runnable() {
        public void run() {
            recyclerView.smoothScrollToPosition(0);
                        }
    },200);

But what I want is to slow down the scrolling speed, so that the complete content gets visible clearly.

Just to improve on the answer a little:

public class SpeedyLinearLayoutManager extends LinearLayoutManager {

    private static final float MILLISECONDS_PER_INCH = 5f; //default is 25f (bigger = slower)

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

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

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

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {

        final LinearSmoothScroller linearSmoothScroller = new LinearSmoothScroller(recyclerView.getContext()) {

            @Override
            public PointF computeScrollVectorForPosition(int targetPosition) {
                return super.computeScrollVectorForPosition(targetPosition);
            }

            @Override
            protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
                return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
            }
        };

        linearSmoothScroller.setTargetPosition(position);
        startSmoothScroll(linearSmoothScroller);
    }
}

And then set SpeedyLayoutManager to your RecyclerView:

recyclerView.setLayoutManager(new SpeedyLinearLayoutManager(context, SpeedyLinearLayoutManager.VERTICAL, false);

For those uninterested in overriding LinearLayoutManager (or whichever subclass you're using), you can just call startSmoothScroll(smoothScroller) directly on the layout manager.

LinearSmoothScroller linearSmoothScroller = new LinearSmoothScroller(recyclerView.getContext()) {

    @Override
    protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
        return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
    }
};

linearSmoothScroller.setTargetPosition(position);
layoutManager.startSmoothScroll(linearSmoothScroller);

I found an answer!

You need to make a custom class extending [LinearLayoutManager][1] and then override the [smoothScrollToPosition][1] method. Inside, you need to create a new [LinearSmoothScroller][1] and override its calculateSpeedPerPixel method Then use that LinearSmoothScroller to complete the scroll.

Here is my example :

public class CustomLinearLayoutManager extends LinearLayoutManager{
        @Override
        public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
            final LinearSmoothScroller linearSmoothScroller =
                    new LinearSmoothScroller(recyclerView.getContext()) {
                        private static final float MILLISECONDS_PER_INCH = 100f;

                        @Override
                        public PointF computeScrollVectorForPosition(int targetPosition) {
                            return CustomLinearLayoutManager.this
                                .computeScrollVectorForPosition(targetPosition);
                    }

                    @Override
                    protected float calculateSpeedPerPixel
                            (DisplayMetrics displayMetrics) {
                        return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
                    }
                };
        linearSmoothScroller.setTargetPosition(position);
        startSmoothScroll(linearSmoothScroller);
    }
}

Assign this CustomLinearLayoutManager to your RecyclerView and you should be good to go. Let me know if I was unclear in anything. I'll be happy to help.

I've made a version that you can set the scrolling speed variable.

If you set factor to 2, it will be twice as slow as default.

public class VariableScrollSpeedLinearLayoutManager extends LinearLayoutManager {

    private final float factor;

    public VariableScrollSpeedLinearLayoutManager(Context context, float factor) {
        super(context);
        this.factor = factor;
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {

        final LinearSmoothScroller linearSmoothScroller = new LinearSmoothScroller(recyclerView.getContext()) {

            @Override
            public PointF computeScrollVectorForPosition(int targetPosition) {
                return VariableScrollSpeedLinearLayoutManager.this.computeScrollVectorForPosition(targetPosition);
            }

            @Override
            protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
                return super.calculateSpeedPerPixel(displayMetrics) * factor;
            }
        };

        linearSmoothScroller.setTargetPosition(position);
        startSmoothScroll(linearSmoothScroller);
    }
}