GridDividerItemDecoration crashes on an empty list

[mobiRic]

GridDividerItemDecoration.drawHorizontalDividers() assumes that the number of items in the list is at least the number of columns in the grid (see View child = parent.getChildAt(i);)

private void drawHorizontalDividers(Canvas canvas, RecyclerView parent) {
    int parentTop = parent.getPaddingTop();
    int parentBottom = parent.getHeight() - parent.getPaddingBottom();

    for (int i = 0; i < mNumColumns; i++) {
        View child = parent.getChildAt(i);
        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

        int parentLeft = child.getRight() + params.rightMargin;
        int parentRight = parentLeft + mHorizontalDivider.getIntrinsicWidth();

        mHorizontalDivider.setBounds(parentLeft, parentTop, parentRight, parentBottom);
        mHorizontalDivider.draw(canvas);
    }
}

There needs to be a null check before the next line that assumes child is not null.

[mobiRic]

Updating to the latest code which is slightly different to v1.0.0 released on maven shows this method (which was introduced in 11a647f):

private void drawHorizontalDividers(Canvas canvas, RecyclerView parent) {
    int childCount = parent.getChildCount();
    int rowCount = childCount / mNumColumns;
    int lastRowChildCount = childCount % mNumColumns;

    for (int i = 1; i < mNumColumns; i++) {
        int lastRowChildIndex;
        if (i < lastRowChildCount) {
            lastRowChildIndex = i + (rowCount * mNumColumns);
        } else {
            lastRowChildIndex = i + ((rowCount - 1) * mNumColumns);
        }

        View firstRowChild = parent.getChildAt(i);
        View lastRowChild = parent.getChildAt(lastRowChildIndex);

        int dividerTop = firstRowChild.getTop();
        int dividerRight = firstRowChild.getLeft();
        int dividerLeft = dividerRight - mHorizontalDivider.getIntrinsicWidth();
        int dividerBottom = lastRowChild.getBottom();

        mHorizontalDivider.setBounds(dividerLeft, dividerTop, dividerRight, dividerBottom);
        mHorizontalDivider.draw(canvas);
    }
}

This still crashes on line int dividerTop = firstRowChild.getTop(); with an empty list, since all child views are null. This will in fact crash for any list with fewer items than columns, sing firstRowChild is trying to find the view to the right of the divider.

Since the commit is the same, I think this is related to #31

[mobiRic]

Apologies - this is a duplicate of #28

I did not originally notice that as I was working with an empty list.