WearableRecyclerView scrolls not curved - android-recyclerview

Question

My WearableRecyclerView the lines go like a triangle and not really curved like the homescreen of the watch. I can't find any mistakes in my code.
ShareActivity:
private void initListView() {
WearableRecyclerView recyclerView = findViewById(R.id.lVDevices);
recyclerView.setEdgeItemsCenteringEnabled(true);
final ScrollingLayoutCallback scrollingLayoutCallback =
new ScrollingLayoutCallback();
adapter = new ShareAdapter(new ShareAdapter.Callback() {
#Override
public void onDeviceClicked(int position, String deviceName) {
onListItemClick(position, deviceName);
}
});
recyclerView.setLayoutManager(
new WearableLinearLayoutManager(this, scrollingLayoutCallback));
recyclerView.setAdapter(adapter);
}
ScrollingLayoutCallback:
public class ScrollingLayoutCallback extends WearableLinearLayoutManager.LayoutCallback {
private static final float MAX_ICON_PROGRESS = 0.65f;
#Override
public void onLayoutFinished(View child, RecyclerView parent) {
// Figure out % progress from top to bottom
float centerOffset = ((float) child.getHeight() / 2.0f) / (float) parent.getHeight();
float yRelativeToCenterOffset = (child.getY() / parent.getHeight()) + centerOffset;
// Normalize for center
float mProgressToCenter = Math.abs(0.5f - yRelativeToCenterOffset);
// Adjust to the maximum scale
mProgressToCenter = Math.min(mProgressToCenter, MAX_ICON_PROGRESS);
child.setScaleX(1 - mProgressToCenter);
child.setScaleY(1 - mProgressToCenter);
}
}
ListView-XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v4.widget.SwipeRefreshLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/refreshlayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/transparent">
<android.support.wear.widget.WearableRecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/lVDevices"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/transparent"
android:scrollbars="vertical"/>
</android.support.v4.widget.SwipeRefreshLayout>
</RelativeLayout>
XML of the row
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/lVDevices_row"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:drawableStart="#drawable/point_img"
android:layout_centerHorizontal="true"
android:textSize="18sp">
</TextView>
Is the problem in the Callback method? I mean is there a mistake in the calculation because it is from the developer website.
Edit 1: New Math in ScrollingCallback class
float centerOffset = ((float) child.getHeight() / 2.0f) / (float) parent.getHeight();
float yRelativeToCenterOffset = (child.getY() / parent.getHeight()) + centerOffset;
float progresstoCenter = (float) Math.sin(yRelativeToCenterOffset * Math.PI);
child.setScaleX(progresstoCenter);
child.setScaleY(progresstoCenter);

Answer 1

I've created a solution.
Like the OP, I never liked the solution given in the official Android documentation, which causes the list elements to move along a triangular path (straight line from the top center to the middle left, and then straight line from there to the bottom center).
The solution is simple, using trig to change the path to semi-circular. Replace the CustomScrollingLayoutCallback with this:
class CustomScrollingLayoutCallback extends WearableLinearLayoutManager.LayoutCallback {
#Override
public void onLayoutFinished(View child, RecyclerView parent) {
final float MAX_ICON_PROGRESS = 0.65f;
try {
float centerOffset = ((float) child.getHeight() / 2.0f) / (float) parent.getHeight();
float yRelativeToCenterOffset = (child.getY() / parent.getHeight()) + centerOffset;
// Normalize for center, adjusting to the maximum scale
float progressToCenter = Math.min(Math.abs(0.5f - yRelativeToCenterOffset), MAX_ICON_PROGRESS);
// Follow a curved path, rather than triangular!
progressToCenter = (float)(Math.cos(progressToCenter * Math.PI * 0.70f));
child.setScaleX (progressToCenter);
child.setScaleY (progressToCenter);
} catch (Exception ignored) {}
}
}
The "... * 0.70f" on that 4th-to-last line was determined by trial-and-error, and alters the curve to best match the official Android Wear curve.