DividerItemDecoration.java

package com.adobe.android.ui.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v4.view.ViewCompat;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.View;

public class DividerItemDecoration extends RecyclerView.ItemDecoration {
    private Drawable mDivider;

    public DividerItemDecoration(Context context, AttributeSet attrs) {
        final TypedArray a = context.obtainStyledAttributes(attrs, new int[]{android.R.attr.listDivider});
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    public DividerItemDecoration(Drawable divider) {
        mDivider = divider;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if (mDivider == null) {
            return;
        }
        if (parent.getChildPosition(view) < 1) {
            return;
        }

        if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
            outRect.top = mDivider.getIntrinsicHeight();
        } else {
            outRect.left = mDivider.getIntrinsicWidth();
        }
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent) {
        if (mDivider == null) {
            super.onDrawOver(c, parent);
            return;
        }

        if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
            final int left = parent.getPaddingLeft();
            final int right = parent.getWidth() - parent.getPaddingRight();
            final int childCount = parent.getChildCount();

            for (int i = 1; i < childCount; i++) {
                final View child = parent.getChildAt(i);

                if (ViewCompat.getAlpha(child) < 1) {
                    continue;
                }

                final float translationY = ViewCompat.getTranslationY(child);
                final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
                final int size = mDivider.getIntrinsicHeight();
                final int top = (int) (child.getTop() + translationY - params.topMargin);
                final int bottom = top + size;
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(c);
            }
        } else { //horizontal
            final int top = parent.getPaddingTop();
            final int bottom = parent.getHeight() - parent.getPaddingBottom();
            final int childCount = parent.getChildCount();

            for (int i = 1; i < childCount; i++) {
                final View child = parent.getChildAt(i);

                if (ViewCompat.getAlpha(child) < 1) {
                    continue;
                }

                final float translationX = ViewCompat.getTranslationX(child);
                final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
                final int size = mDivider.getIntrinsicWidth();
                final int left = (int) (child.getLeft() + translationX - params.leftMargin);
                final int right = left + size;
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(c);
            }
        }
    }

    private int getOrientation(RecyclerView parent) {
        if (parent.getLayoutManager() instanceof LinearLayoutManager) {
            LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
            return layoutManager.getOrientation();
        } else {
            throw new IllegalStateException("DividerItemDecoration can only be used with a LinearLayoutManager.");
        }
    }

}