Android自定义ViewGroup控件中两种方式获取的宽度为什么不一样

通过getLayoutParams().width和getMeasuredWidth()获取的宽度为什么不一样
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

    View menuView=getChildAt(0);//得到menu控件
    menuView.measure(menuView.getLayoutParams().width,heightMeasureSpec);
    System.out.println("布局宽度-----------"+menuView.getLayoutParams().width);
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
     protected void onLayout(boolean changed, int l, int t, int r, int b) {
    View menuView=getChildAt(0);
    menuView.layout(-menuView.getLayoutParams().width,t,0,b);
    menuWidth = menuView.getLayoutParams().width;
    System.out.println("getMeasured宽度：：：：："+menuView.getMeasuredWidth());
            }