A search bar provides an interface for text-based searches with a text box and buttons such as search and cancel. A search bar
accepts text from users, which can be used as input for a search (shown here with placeholder text). A scope bar, which is available only in conjunction with a search bar—allows users to define the scope of a search (shown here below a search bar).
search bar提供了一个带有搜索、取消按钮以及文本框的基于文本搜索的界面。search bar接收用户输入的文本，用这些文本来作为搜索条件进行搜索（在这里显示为占位符）。scope
bar，它只能连同search bar一起显示，允许用户定义搜索范围（下面显示就是一个search bar）。
Purpose. Search bars allow users to:
Search Bars（一）
原文：http://blog.csdn.net/debolee/article/details/46414695
