RecyclerView的LinearLayoutManager

public class DividerItemDecoration extends RecyclerView.ItemDecoration {
    private Paint mPaint;
    private int mDividerHeight = 2;//分割线高度，默认为1px

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

    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;

    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;

    private Drawable mDivider;

    private int mOrientation;

    public DividerItemDecoration(Context context, int orientation, int dividerColor) {
         final TypedArray a = context.obtainStyledAttributes(ATTRS );
        mDivider = a.getDrawable(0);
        a.recycle();
        setOrientation(orientation);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(dividerColor);
        mPaint.setStyle(Paint.Style.FILL);
    }

    public void setOrientation( int orientation) {
        if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
            throw new IllegalArgumentException( "invalid orientation");
        }
        mOrientation = orientation;
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int childCount = parent.getChildCount();
        int p = parent.getItemDecorationCount();

        for (int i = 0; i < childCount -1 ; i++) {
            if (mOrientation == VERTICAL_LIST) {
                drawVertical(c, parent);
            } else {
                drawHorizontal(c, parent);
            }
        }
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent) {

    }

    public void drawHorizontal(Canvas c, 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(c);
            }
            if (mPaint != null) {
                c.drawRect(left, top, right, bottom, mPaint);
            }
        }
    }

    public void drawVertical(Canvas c, 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(c);
            }
            if (mPaint != null) {
                c.drawRect(left, top, right, bottom, mPaint);
            }
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
        if (mOrientation == VERTICAL_LIST) {
            if (itemPosition != 2) {
                outRect.set(5, 0, 5, mDivider.getIntrinsicHeight());
            }
        }else{
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}