Android GUI Building Blocks

说明：此笔记为“Android开发”学习视频的笔记，链接如下：http://open.163.com/movie/2010/1/8/D/M79HE97C3_M79HEQJ8D.html

一, Activity: A represnetation of a user doing something,

例子：显示联系人列表并且选中一个联系人

Activity的三种状态：Stopped， Paused，Active

二, Service: an application or an applicaton component that doesn't have a user interface

例子：媒体播放器

三, Broadcast Receiver:

1,Receive and react to "broadcasts"

2,Don't have a user interface, but can invoke Activities that do

3,Create by extending the Android BroadcastReceiver class

4,Example: An application wants to be notified when a photo is taken on the device

四，Content Provider

1，Make's an application's data avaliable to other apps, and can also be used by the defining app itself

2, Example: Make contacts avaliable to other apps

五，Intents： An “intent” is an asynchrounous message sent from one Activity to another