Service详解

 /**
  *  后台执行的定时任务
  */
 public class LongRunningService extends Service {

     @Override
     public IBinder onBind(Intent intent) {
         return null;
     }

     @Override
     public int onStartCommand(Intent intent,int flags,int startId) {

         new Thread(){
             public void run() {
                 Log.i("TAG","LongRunningService exec at " + new Date().toString());
             };
         }.start();

         //获取Alarm管理对象
         AlarmManager manager = (AlarmManager)getSystemService(ALARM_SERVICE);

         //设置执行的时间间隔
         long triggerAtTime = SystemClock.elapsedRealtime() + 5 * 1000; 

         //获取一个能够执行广播的 PendingIntent。 这样当定时任务被触发的时候，广播接收器的
          onReceive()方法就可以得到执行。
         Intent intent2 = new Intent(this,AlarmReceiver.class);
         PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent2, 0);

         //设置一个定时任务
         manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtTime, pendingIntent);
         return super.onStartCommand(intent,flags,startId);
     }
 }

 public class AlarmReceiver extends BroadcastReceiver {
     @Override
     public void onReceive(Context context,Intent intent) {
         Intent intent2 = new Intent(context, LongRunningService.class);
         context.startService(intent2);
     }
 }

 /**
  *  前台服务
  */
 public class ForegroundService extends Service {

     @Override
     public IBinder onBind(Intent intent) {
         return null;
     }

     @Override
     public void onCreate() {
         Intent intent = new Intent(this,MainActivity.class);
         PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent,0);

         Notification nf = new Notification(R.drawable.p1,"有一条通知",System.currentTimeMillis());
         nf.setLatestEventInfo(this,"这是通知的标题","这是通知的内容",pendingIntent);
         nf.flags = Notification.FLAG_AUTO_CANCEL;
         //调用这个方法将服务变为前台服务，并在系统通知栏显示出来
         startForeground(1,nf);

         super.onCreate();
     }
 }