Android LinearSnapHelper - how to increase scrolling/"snapping" speed?

Question

I'm using a LinearSnapHelper to make items in my RecyclerView "snap" into place on the screen (my cards take up most of the screen, so I want them to snap into place and fill the screen on every swipe/fling/scroll).

I'm struggling with how to make the cards snap into place faster. I've tried creating a custom LinearLayoutManager (and editing the calculateSpeedPerPixel method in scrollToPosition or smoothScrollToPosition), as well as a custom RecyclerView (and editing the fling method). But nothing effects the speed that cards "snap" into place.

I suppose the issue is that I don't really understand how LinearSnapHelper "scrolls" the cards into position. It doesn't seem to use LinearLayoutManager's scrollToPosition or smoothScrollToPosition methods.

    snapHelper = new LinearSnapHelper() {
        @Override
        public int findTargetSnapPosition(RecyclerView.LayoutManager layoutManager, int velocityX, int velocityY) {
            View centerView = findSnapView(layoutManager);
            if (centerView == null) {
                return RecyclerView.NO_POSITION;
            }

            int position = layoutManager.getPosition(centerView);
            int targetPosition = -1;
            if (layoutManager.canScrollHorizontally()) {
                if (velocityX < 0) {
                    targetPosition = position - 1;
                } else {
                    targetPosition = position + 1;
                }
            }

            if (layoutManager.canScrollVertically()) {
                if (velocityY > 0) {
                    targetPosition = position + 1;
                } else {
                    targetPosition = position - 1;
                }
            }

            final int firstItem = 0;
            final int lastItem = layoutManager.getItemCount() - 1;
            targetPosition = Math.min(lastItem, Math.max(targetPosition, firstItem));
            return targetPosition;
        }
    };
    snapHelper.attachToRecyclerView(mRecyclerView);

devilbrain666 · Answer 1 · 2017-08-23T09:22:09.357

As 郭玉龙 mentioned, SnapHelper call RecyclerView.smoothScrollBy() method. And it use default sQuinticInterpolator. To change speed of snap you can do next:

public class SlowdownRecyclerView extends RecyclerView {

// Change pow to control speed.
// Bigger = faster. RecyclerView default is 5.
private static final int POW = 2;

private Interpolator interpolator;

public SlowdownRecyclerView(Context context) {
    super(context);
    createInterpolator();
}

public SlowdownRecyclerView(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    createInterpolator();
}

public SlowdownRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    createInterpolator();
}

private void createInterpolator(){
    interpolator = new Interpolator() {
        @Override
        public float getInterpolation(float t) {
            t = Math.abs(t - 1.0f);
            return (float) (1.0f - Math.pow(t, POW));
        }
    };
}

@Override
public void smoothScrollBy(int dx, int dy) {
    super.smoothScrollBy(dx, dy, interpolator);
}

Or you can implement your own interpolator.

score 3 · Answer 2 · edited May 21 '18 at 08:48

3

The speed of snapping scroll is affected by RecyclerView.smoothScrollBy().

Here's the snippet of source code.

Override this function to increase or decrease the speed of snapping scroll.

edited May 21 '18 at 08:48

Abu Yousuf

4,421
2
23
39

answered Jan 17 '17 at 08:34

郭玉龙

61
9

score 2 · Answer 3 · answered Nov 05 '16 at 04:40

I wound up doing this by adding a ScrollListener to my RecycleView, and then creating a custom LinearLayoutManager and custom smoothScrollToPosition method.

    final CustomLinearLayoutManager mLayoutManager = new CustomLinearLayoutManager(getActivity());
    mRecyclerView.setLayoutManager(mLayoutManager);

    mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        private boolean scrollingUp;

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            scrollingUp = dy < 0;
        }

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                int visiblePosition = scrollingUp ? mLayoutManager.findFirstVisibleItemPosition() : mLayoutManager.findLastVisibleItemPosition();
                int completelyVisiblePosition = scrollingUp ? mLayoutManager
                        .findFirstCompletelyVisibleItemPosition() : mLayoutManager
                        .findLastCompletelyVisibleItemPosition();
                if (visiblePosition != completelyVisiblePosition) {
                    recyclerView.smoothScrollToPosition(visiblePosition);
                    return;
                }
        }
    });

why does your linear layout as to be custom, have you tried it with standard horizontal linear layout ? — 2cupsOfTech, May 23 '17 at 11:07
You need the CustomLinearLayoutManager to speed up the snap/scroll speed. Here is an example https://stackoverflow.com/a/36784136/ — Jerry Sha, Jan 04 '19 at 19:29

Rohan Arora · Answer 4 · 2021-01-29T06:00:12.063

I achieved this using a library https://github.com/rubensousa/GravitySnapHelper

you can also override findTargetSnapPosition to get pager like scroll

tweek the scrollMsPerInch to increase / decrease speed

    val snapHelper : GravitySnapHelper = GravitySnapHelper(Gravity.CENTER)
    
    // the lower the higher the speed, default is 100f
    snapHelper.scrollMsPerInch = 40f

    snapHelper.attachToRecyclerView(binding?.mRecyclerView)

score -1 · Answer 5 · answered Jun 18 '19 at 20:58

-1

Actually you can modify the LinearSnapHelper and SnapHelperClass by simply copy/paste the existing code the only thing you will do is to set MILLISECONDS_PER_INCH on SnapHelper as you want and then use simply use the LinearSnapHelper you created

answered Jun 18 '19 at 20:58

Nassim Nassim Youssef

25
3

Android LinearSnapHelper - how to increase scrolling/"snapping" speed?

5 Answers5