Service kill 掉之后有重新restart

1. http://blog.csdn.net/mjm0771/article/details/6701023

最近项目中遇到一个问题：程序在系统注册了broadcastreceiver来监听启动通知，在onReceive中启动了一个service通过service的onStart来启动程序。问题在于，程序退出时没有stop这个service，之后当系统正常运行一段时间（1-2小时），程序突然自动启动，查看log后发现这样几句：

1service运行方式

如果使用startService()启动service，系统将通过传入的Intent在底层搜索相关符合Intent里面信息的service。如果服务没有启动则先运行onCreate，然后运行onStartCommand （可在里面处理启动时传过来的Intent和其他参数），直到明显调用stopService或者stopSelf才将停止Service。无论运行startService多少次，只要调用一次stopService或者stopSelf，Service都会停止。使用stopSelf(int)方法可以保证在处理好intent后再停止。

onStartCommand 的原型为 public int onStartCommand(Intent intent, int flags, int startId) ，在2.0后被引入用于service的启动函数，2.0之前为public void onStart(Intent intent, int startId) 。

这里onStartCommand 函数返回一个整形值：

1、START_STICKY

2、START_NOT_STICKY

3、START_REDELIVER_INTENT

 

对于1的解释：

Constant to return from onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from onStartCommand(Intent, int, int)), then leave it in the started state but don't retain this delivered intent. Later the system will try to re-create the service. Because it is in the started state, it will guarantee to callonStartCommand(Intent, int, int) after creating the new service instance; if there are not any pending start commands to be delivered to the service, it will be called with a null intent object, so you must take care to check for this.

在运行onStartCommand后service进程被kill后，那将保留在开始状态，但是不保留那些传入的intent。不久后service就会再次尝试重新创建，因为保留在开始状态，在创建     service后将保证调用onstartCommand。如果没有传递任何开始命令给service，那将获取到null的intent。

 

对于2的解释：

Constant to return from onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from onStartCommand(Intent, int, int)), and there are no new start intents to deliver to it, then take the service out of the started state and don't recreate until a future explicit call toContext.startService(Intent). The service will not receive aonStartCommand(Intent, int, int) call with a null Intent because it will not be re-started if there are no pending Intents to deliver.

在运行onStartCommand后service进程被kill后，并且没有新的intent传递给它。Service将移出开始状态，并且直到新的明显的方法（startService）调用才重新创建。因为如果没有传递任何未决定的intent那么service是不会启动，也就是期间onstartCommand不会接收到任何null的intent。

 

对于3的解释：

Constant to return from onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from onStartCommand(Intent, int, int)), then it will be scheduled for a restart and the last delivered Intent re-delivered to it again via onStartCommand(Intent, int, int). This Intent will remain scheduled for redelivery until the service calls stopSelf(int) with the start ID provided toonStartCommand(Intent, int, int). The service will not receive aonStartCommand(Intent, int, int) call with a null Intent because it will will only be re-started if it is not finished processing all Intents sent to it (and any such pending events will be delivered at the point of restart).

在运行onStartCommand后service进程被kill后，系统将会再次启动service，并传入最后一个intent给onstartCommand。直到调用stopSelf(int)才停止传递intent。如果在被kill后还有未处理好的intent，那被kill后服务还是会自动启动。因此onstartCommand不会接收到任何null的intent。

 

当service运行在低内存的环境时，将会kill掉一些存在的进程。因此进程的优先级将会很重要，可以使用startForeground API将service放到前台状态。这样在低内存时被kill的几率更低，但是如果在极度极度低内存的压力下，该service还是会被kill掉。