摘要：
Android 应用程序四个模块：1. Activity:称之为“活动”，在应用程序中，一个activity通常就是一个屏幕。每个活动都被实现为独立的类，并将显示由视图控件组成的用户接口，对事件作出响应。An activity represents a single screen with a user interface. For example, an email application might have one activity that shows a list of new emails, another activity to compose an email, and ano 阅读全文