首先是Service的周期问题 
The service will at this point continue running until Context.stopService() or stopSelf() is called. Note that multiple calls to Context.startService() do not nest (though they do result in multiple corresponding calls to onStartCommand()), so no matter how many times it is started a service will be stopped once Context.stopService() or stopSelf() is called 
上面是android的HP上写的关于Service周期的一段话，是说，Service在开始以后，除非调用了Context.stopService()或者stopSelf()，否则不会停止。当然如果内存不足，系统可能自动杀死Service。 


下面是关于ServiceConnection接口的： 

private ServiceConnection conn = new ServiceConnection() {

		@Override
		public void onServiceDisconnected(ComponentName name) {
			// TODO Auto-generated method stub
			
			mService = null;
			
		}

		@Override
		public void onServiceConnected(ComponentName name, IBinder service) {
			// TODO Auto-generated method stub
			mService = IBindService.Stub.asInterface(service);
			
		}
	};

貌似现在的主流写法是这样。下面的代码的bindService method执行之后会自动调用上面ServiceConnection接口里的onServiceConnected method 

				Intent intent = new Intent(IBindService.class.getName());
				bindService(intent, conn, BIND_AUTO_CREATE);

人会想，如果执行unbindService之后不就自动调用ServiceConnection接口里的onServiceDisconnected method了吗。 

其实不然，查看api，你会发现，ServiceConnection接口里德onServiceDisconnected method只会在Service被停止或者被系统杀死以后调用。 

也就是说你执行unbindService 只是告诉系统你已经和这个服务没有关系了。系统在内存不足的时候可以优先杀死这个服务而已。