Android依次(自层次树顶层开始)解析你布局中的元素，实例化View并将它们添加到它们的父节点中。
Android parses the elements of your layout in-order (from the top of the hierarchy tree), instantiating the Views and adding them to their parent (s).
树顶部的books节点有两个book子标记。
The books node at the top of the tree has two child book tags.
应用推荐