Application Fundamentals--Broadcast receiver lifecycle（广播接收组件生命周期）

Broadcast receiver lifecycle---广播接收组件生命周期

A broadcast receiver has single callback method:--翻译：广播接收组件只有唯一一个回调方法：

void onReceive(Context curContext, Intent broadcastMsg)

   When a broadcast message arrives for the receiver, Android calls its onReceive()广播接收组件 method and passes it the Intent object containing the message. The broadcast receiver is considered to be active only while it is executing this method. When onReceive() returns, it is inactive.

当消息接受者接到广播消息，Android将立刻调用广播接收组件实例的 onReceive()方法，同时,消息封装在intent对象中以参数的方式传入该方法，该方法执行过程中，该广播接收组件实例的状态是活动状态。广播接收组件实例的onReceive()一旦执行完毕，广播接收组件实例的状态变为非活动状态。

   A process with an active broadcast receiver is protected from being killed. But a process with only inactive components can be killed by the system at any time, when the memory it consumes is needed by other processes.

翻译：活动状态的广播接收组件实例所属的进程是受系统保护的，不会被系统关闭的。但是对于非活动状态的广播接收组件实例所属的进程而言，一旦出现系统资源缺乏，为了腾出必要内存空间，系统随时可以杀死该进程。

   This presents a problem when the response to a broadcast message is time consuming and, therefore, something that should be done in a separate thread, away from the main thread where other components of the user interface run. If onReceive() spawns the thread and then returns, the entire process, including the new thread, is judged to be inactive (unless other application components are active in the process), putting it in jeopardy of being killed. The solution to this problem is for onReceive() to start a service and let the service do the job, so the system knows that there is still active work being done in the process.

翻译：需要注意的是，如果说对广播消息的响应是耗时操作的话（onReceive()方法中的代码），就需要考虑脱离主线程、以独立线程方式执行对消息的响应处理，这样可以避免阻塞现象的发生（寄宿在主线程之上的其他组件实例与用户交互过程被阻塞）。如果在onReceive()方法中在当前进程中创建一个独立的线程，该方法执行完毕后，当前进程可能被系统就认定为惰性进程（如果此时进程中的其他组件实例都处于惰性状态），当前进程是随时可能被系统关闭的。对这个问题的解决方式是：在onReceive()方法中以服务的方式来处理对消息的响应，这样可以使得系统认为当前进程依然是活动状态，避免被系统杀死。

The next section has more on the vulnerability of processes to being killed.