效果图：

用法：

加入默认切割线：高度为2px。颜色为灰色

mRecyclerView.addItemDecoration(new RecycleViewDivider(mContext, LinearLayoutManager.VERTICAL));

加入自己定义切割线：可自己定义切割线drawable

mRecyclerView.addItemDecoration(new RecycleViewDivider(

    mContext, LinearLayoutManager.VERTICAL, R.drawable.divider_mileage));

加入自己定义切割线：可自己定义切割线高度和颜色

mRecyclerView.addItemDecoration(new RecycleViewDivider(

    mContext, LinearLayoutManager.VERTICAL, 10, getResources().getColor(R.color.divide_gray_color)));

万能切割线登场：

public class RecycleViewDivider extends RecyclerView.ItemDecoration {

    private Paint mPaint;

    private Drawable mDivider;

    private int mDividerHeight = 2;//切割线高度，默觉得1px

    private int mOrientation;//列表的方向：LinearLayoutManager.VERTICAL或LinearLayoutManager.HORIZONTAL

    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};

    /**

     * 默认切割线：高度为2px，颜色为灰色

     *

     * @param context

     * @param orientation 列表方向

     */

    public RecycleViewDivider(Context context, int orientation) {

        if (orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL) {

            throw new IllegalArgumentException("请输入正确的參数！

");

        }

        mOrientation = orientation;

        final TypedArray a = context.obtainStyledAttributes(ATTRS);

        mDivider = a.getDrawable(0);

        a.recycle();

    }

    /**

     * 自己定义切割线

     *

     * @param context

     * @param orientation 列表方向

     * @param drawableId  切割线图片

     */

    public RecycleViewDivider(Context context, int orientation, int drawableId) {

        this(context, orientation);

        mDivider = ContextCompat.getDrawable(context, drawableId);

        mDividerHeight = mDivider.getIntrinsicHeight();

    }

    /**

     * 自己定义切割线

     *

     * @param context

     * @param orientation   列表方向

     * @param dividerHeight 切割线高度

     * @param dividerColor  切割线颜色

     */

    public RecycleViewDivider(Context context, int orientation, int dividerHeight, int dividerColor) {

        this(context, orientation);

        mDividerHeight = dividerHeight;

        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

        mPaint.setColor(dividerColor);

        mPaint.setStyle(Paint.Style.FILL);

    }

    //获取切割线尺寸

    @Override

    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {

        super.getItemOffsets(outRect, view, parent, state);

        outRect.set(0, 0, 0, mDividerHeight);

    }

    //绘制切割线

    @Override

    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {

        super.onDraw(c, parent, state);

        if (mOrientation == LinearLayoutManager.VERTICAL) {

            drawVertical(c, parent);

        } else {

            drawHorizontal(c, parent);

        }

    }

    //绘制横向 item 切割线

    private void drawHorizontal(Canvas canvas, RecyclerView parent) {

        final int left = parent.getPaddingLeft();

        final int right = parent.getMeasuredWidth() - parent.getPaddingRight();

        final int childSize = parent.getChildCount();

        for (int i = 0; i < childSize; i++) {

            final View child = parent.getChildAt(i);

            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();

            final int top = child.getBottom() + layoutParams.bottomMargin;

            final int bottom = top + mDividerHeight;

            if (mDivider != null) {

                mDivider.setBounds(left, top, right, bottom);

                mDivider.draw(canvas);

            }

            if (mPaint != null) {

                canvas.drawRect(left, top, right, bottom, mPaint);

            }

        }

    }

    //绘制纵向 item 切割线

    private void drawVertical(Canvas canvas, RecyclerView parent) {

        final int top = parent.getPaddingTop();

        final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();

        final int childSize = parent.getChildCount();

        for (int i = 0; i < childSize; i++) {

            final View child = parent.getChildAt(i);

            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();

            final int left = child.getRight() + layoutParams.rightMargin;

            final int right = left + mDividerHeight;

            if (mDivider != null) {

                mDivider.setBounds(left, top, right, bottom);

                mDivider.draw(canvas);

            }

            if (mPaint != null) {

                canvas.drawRect(left, top, right, bottom, mPaint);

            }

        }

    }

}

附：自定的drawable文件一份

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"

    android:shape="rectangle">

    <size android:height="20dp" />

    <solid android:color="#ff992900" />

</shape>