终止服务

Question

我正在阅读有关Android服务的信息，尤其是我想到了这一点

  

一个应用程序位于前台时，它可以创建并运行两个应用程序   免费提供前台和后台服务。当应用进入   背景，它有一个几分钟的窗口，它仍然在   允许创建和使用服务。在该窗口的结尾，该应用   被认为是空闲的。此时，系统会停止该应用的   后台服务，就像该应用已调用了“服务”   Service.stopSelf（）方法。

在下面的代码中，当应用程序在大约一分钟后进入后台时，服务被销毁，但线程仍在执行。

1. 那么终止服务的目的是什么？进程/线程仍在执行。

2. 为什么首先要终止服务？如果我要执行下载过程而不希望成为前台进程怎么办？

   public class HelloService extends Service {
   private Looper mServiceLooper;
   private ServiceHandler mServiceHandler;
   
   // Handler that receives messages from the thread
   private final class ServiceHandler extends Handler {
       public ServiceHandler(Looper looper) {
           super(looper);
       }
       @Override
       public void handleMessage(Message msg) {
           // Normally we would do some work here, like download a file.
           // For our sample, we just sleep for 5 seconds.
           Log.d("sssssssss",msg.toString()+"sssssssssss");
           while(true){
   
               Log.d("sssssssss","sssssssssss");
   
           }
           // Stop the service using the startId, so that we don't stop
           // the service in the middle of handling another job
           //stopSelf(msg.arg1);
       }
   }
   
   @Override
   public void onCreate() {
       // Start up the thread running the service. Note that we create a
       // separate thread because the service normally runs in the process's
       // main thread, which we don't want to block. We also make it
       // background priority so CPU-intensive work doesn't disrupt our UI.
       HandlerThread thread = new HandlerThread("ServiceStartArguments",
               Process.THREAD_PRIORITY_BACKGROUND);
       thread.start();
   
       // Get the HandlerThread's Looper and use it for our Handler
       mServiceLooper = thread.getLooper();
       mServiceHandler = new ServiceHandler(mServiceLooper);
   }
   
   @Override
   public int onStartCommand(Intent intent, int flags, int startId) {
       Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();
   
       // For each start request, send a message to start a job and deliver the
       // start ID so we know which request we're stopping when we finish the job
       Message msg = mServiceHandler.obtainMessage();
       msg.arg1 = startId;
       mServiceHandler.sendMessage(msg);
   
       // If we get killed, after returning from here, restart
       return START_STICKY;
   }
   
   @Override
   public void onDestroy() {
       Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
   }
   
   
   
   @Nullable
   @Override
   public IBinder onBind(Intent intent) {
       return null;
   }
   }
   

Answer 1

1. 系统允许您通过触发其destroy方法来对Service执行干净的处理。您的线程不会永远运行，我认为30分钟是在终止应用程序进程之前的硬限制。
2. 这是自android O以来的新政策，旨在延长电池寿命并提高性能。许多开发人员在后台执行繁重的操作（套接字不间断打开，定期读取传感器读数等），并且在没有前台通知的情况下，用户不知道其设备为何呆滞且电池正常运行时间较差。

详细了解Background Execution Limits文档。