A RecyclerView.ItemDecoration that adds 8 dp padding to the top of the first and bottom of the last item in a list (or RecyclerView in this case).

ListPaddingDecoration.java

import android.content.Context;
import android.graphics.Rect;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.View;

/**
 * Adds 8dp padding to the top of the first and the bottom of the last item in the list,
 * as specified in https://www.google.com/design/spec/components/lists.html#lists-specs
 */
public class ListPaddingDecoration extends RecyclerView.ItemDecoration {
    private final static int PADDING_IN_DIPS = 8;
    private final int mPadding;

    public ListPaddingDecoration(@NonNull Context context) {
        DisplayMetrics metrics = context.getResources().getDisplayMetrics();
        mPadding = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, PADDING_IN_DIPS, metrics);
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        final int itemPosition = parent.getChildAdapterPosition(view);
        if (itemPosition == RecyclerView.NO_POSITION) {
            return;
        }
        if (itemPosition == 0) {
            outRect.top = mPadding;
        }

        final RecyclerView.Adapter adapter = parent.getAdapter();
        if ((adapter != null) && (itemPosition == adapter.getItemCount() - 1)) {
            outRect.bottom = mPadding;
        }
    }

}

You should rename it to ListMarginDecoration

I think the idea is that this margin creates the illusion of padding.

If you want to set padding this way, you should use View instead of Rect inside getItemOffsets.
For example view.setPadding(0, mPadding, 0, 0) for top padding and view.setPadding(0, 0, 0, mPadding)