一、Context.startService()
* 声明周期：
Service中 Context中
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onCreate() <----startService()
onStartCommand()
onDestory() <----stopService() / Service#stopSelf()
二、Context.bindService()
* 声明周期：
Service中 Context中
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onCreate() <----bindService()
onBind()
onUnbind() <----unBindService()
onDestory()
