RecyclerView 使用 GridLayoutManager 为什么无法均匀分布？

 private void updateMeasurements() {        int totalSpace;        if (getOrientation() == VERTICAL) {            totalSpace = getWidth() - getPaddingRight() - getPaddingLeft();        } else {            totalSpace = getHeight() - getPaddingBottom() - getPaddingTop();        }        calculateItemBorders(totalSpace); // 计算每一个表格中子View的边界    }
    @Override    public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec) {        if (mCachedBorders == null) {            super.setMeasuredDimension(childrenBounds, wSpec, hSpec);        }        final int width, height;        final int horizontalPadding = getPaddingLeft() + getPaddingRight();        final int verticalPadding = getPaddingTop() + getPaddingBottom();        if (mOrientation == VERTICAL) { // 垂直方向列表            final int usedHeight = childrenBounds.height() + verticalPadding;            height = chooseSize(hSpec, usedHeight, getMinimumHeight());            width = chooseSize(wSpec, mCachedBorders[mCachedBorders.length - 1] + horizontalPadding,                    getMinimumWidth()); // 综合计算 子View的宽度        } else {            final int usedWidth = childrenBounds.width() + horizontalPadding;            width = chooseSize(wSpec, usedWidth, getMinimumWidth());            height = chooseSize(hSpec, mCachedBorders[mCachedBorders.length - 1] + verticalPadding,                    getMinimumHeight());        }        setMeasuredDimension(width, height);    }
    /**     * @param totalSpace Total available space after padding is removed     */    private void calculateItemBorders(int totalSpace) {        mCachedBorders = calculateItemBorders(mCachedBorders, mSpanCount, totalSpace);    }
    /**     * @param cachedBorders The out array     * @param spanCount number of spans     * @param totalSpace total available space after padding is removed     * @return The updated array. Might be the same instance as the provided array if its size     * has not changed.     */    static int[] calculateItemBorders(int[] cachedBorders, int spanCount, int totalSpace) {        if (cachedBorders == null || cachedBorders.length != spanCount + 1                || cachedBorders[cachedBorders.length - 1] != totalSpace) {            cachedBorders = new int[spanCount + 1];        }        cachedBorders[0] = 0;        int sizePerSpan = totalSpace / spanCount; // 计算每一个子View的宽度        int sizePerSpanRemainder = totalSpace % spanCount; // 计算剩余总空间大小        int consumedPixels = 0;        int additionalSize = 0;        for (int i = 1; i <= spanCount; i++) { // spanCount表示一行有几列，            int itemSize = sizePerSpan;            additionalSize += sizePerSpanRemainder;            if (additionalSize > 0 && (spanCount - additionalSize) < sizePerSpanRemainder) {                itemSize += 1;                additionalSize -= spanCount;            }            consumedPixels += itemSize;            cachedBorders[i] = consumedPixels;        }        return cachedBorders;    }

        /**         * Chooses a size from the given specs and parameters that is closest to the desired size         * and also complies with the spec.         *         * @param spec The measureSpec         * @param desired The preferred measurement         * @param min The minimum value         *         * @return A size that fits to the given specs         */        public static int chooseSize(int spec, int desired, int min) {            final int mode = View.MeasureSpec.getMode(spec);            final int size = View.MeasureSpec.getSize(spec);            switch (mode) {                case View.MeasureSpec.EXACTLY:                    return size;                case View.MeasureSpec.AT_MOST:                    return Math.min(size, Math.max(desired, min));                case View.MeasureSpec.UNSPECIFIED:                default:                    return Math.max(desired, min);            }        }