measure

在还没有构建View 之前无法取得View的度宽。
在此之前我们必须 先 measure 一下.


测量的三种模式：
UNSPECIFIED: 不限定
EXACTLY: 固定
AT_MOST:最多

view.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);
measure()后调用

getMeasuredWidth()和

getMeasuredHeight()得到测量后的值。

 

 

    private void measureView(View child) {
        ViewGroup.LayoutParams p = child.getLayoutParams();
        if (p == null) {
            p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT);
        }
        int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
        int lpHeight = p.height;
        int childHeightSpec;
        if (lpHeight > 0) {
            childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,MeasureSpec.EXACTLY);
        } else {
            childHeightSpec = MeasureSpec.makeMeasureSpec(0,MeasureSpec.UNSPECIFIED);
        }
       child.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);
        child.measure(childWidthSpec, childHeightSpec);
    }