父容器调用getChildMeasureSpec的时候传入的第二个参数好像不止是子view的padding吧？这是怎么回事？

Question

/**

 * Ask one of the children of this view to measure itself, taking into

 * account both the MeasureSpec requirements for this view and its padding

 * and margins. The child must have MarginLayoutParams The heavy lifting is

 * done in getChildMeasureSpec.

 *

 * @param child The child to measure

 * @param parentWidthMeasureSpec The width requirements for this view

 * @param widthUsed Extra space that has been used up by the parent

 *        horizontally (possibly by other children of the parent)

 * @param parentHeightMeasureSpec The height requirements for this view

 * @param heightUsed Extra space that has been used up by the parent

 *        vertically (possibly by other children of the parent)

 */

protected void measureChildWithMargins(View child,

        int parentWidthMeasureSpec, int widthUsed,

        int parentHeightMeasureSpec, int heightUsed) {

    // 1 类型转换

    final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();

 

 

    // 2 getChildMeasureSpec方法

    final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,

            mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin

                    + widthUsed, lp.width);

    final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,

            mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin

                    + heightUsed, lp.height);

 

 

    child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

}

/**
* @param spec 父View的详细测量值（MeasureSpec）
* @param padding  子view内外边距
*@param childDimension 子view预定的大小(LayoutParam.width或height)---最终不一定绘制该大小
*子布局大小需要由自身的layoutPrams属性和父View的MeasureSpec共同决定
*/
ViewGroup.getChildMeasureSpec(int spec, int padding, int childDimension);