1. Activity
   1. 启动模式
      1. standard
      2. singleTop
      3. singleTask
      4. singleInstance
   2. ActivityCollector
2. Services
   1. 异步消息处理机制
      1. Message
      2. Handler
      3. MessageQueue
      4. Looper
3. Broadcast
   1. Normal broadcasts
   2. Ordered broadcasts
   3. 本地广播-LocalBroadcastManager
   4. 广播的接受（BroadcastReceiver）
   5. 广播的发送
      1. 标准广播-Intent-sendBroadcast
      2. 有序广播-Intent-sendOrderedBroadcast
4. Content Provider