1，从官网上可以看出google为了系统更加流畅以及优化内存，Google做了很大的处理，在手机暗屏或者睡眠状态就停止后台运行；若要保持service的常驻，需要做一些前端的活动，Notification重要属性：notification.flags = Notification.FLAG_NO_CLEAR|Notification.FLAG_ONGOING_EVENT;然后startForeground(setClass().hashCode(), notification);使得服务能挂在通知栏。

2，通过wakelock占用CPU，若一直占用CPU的话，当然这是比较耗电的，要是耗电太高的话系统会直接回收，杀死程序进程。

我是使用定时器唤醒cpu 后台服务将接收到定时任务执行未完成的任务：下面是我实现的代码

在mainfest中注册

<uses-permission android:name="android.permission.WAKE_LOCK"/><uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>复制代码

<receiver android:name=".receiver.WakeCPUAlarmReceiver"/><service
    android:name="com.txtws.wakeloackdemo.service.WakecpuIntentService" ></service>复制代码

关键代码定时任务：

public  void startAlarm(Context context){
      Intent intent = new Intent(context, WakeCPUAlarmReceiver.class);
      alarmIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
      alarmMgr = (AlarmManager) context
            .getSystemService(Context.ALARM_SERVICE);//    alarmMgr.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,//          1000, alarmIntent);
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
         alarmMgr.setExactAndAllowWhileIdle(
               AlarmManager.ELAPSED_REALTIME_WAKEUP,
               SystemClock.elapsedRealtime() + chekcTime, alarmIntent);
      } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
         alarmMgr.setExact(AlarmManager.ELAPSED_REALTIME_WAKEUP,
               SystemClock.elapsedRealtime() + chekcTime, alarmIntent);
      } else {
         alarmMgr.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,
               SystemClock.elapsedRealtime() + chekcTime, alarmIntent);
       FileLogUtil.e(TAG , "startAlarm 设置定时任务");
   }复制代码

接收到定时任务：

public class WakeCPUAlarmReceiver extends WakefulBroadcastReceiver {    private  AlarmManager alarmMgr;    private  PendingIntent alarmIntent;    private  final long chekcTime = 30* 1000;
    public static boolean isCheckFlag = false;   private static String TAG = WakeCPUAlarmReceiver.class.getSimpleName();   @Override
   public void onReceive(Context context, Intent intent) {      // TODO Auto-generated method stub
          Intent service = new Intent(context, WakecpuIntentService.class);          FileLogUtil.e(TAG , "onReceive 接收定时任务");
          startWakefulService(context, service);
   }复制代码

在service中执行需要执行的任务：

public class WakecpuIntentService extends IntentService {   private static String TAG = WakecpuIntentService.class.getSimpleName() + " :";   private NotificationManager mNotificationManager;   private PowerManager.WakeLock wl;   NotificationCompat.Builder builder;
   public WakecpuIntentService() {      super("WakecpuIntentService");      // TODO Auto-generated constructor stub
   }   @Override
   protected void onHandleIntent(Intent intent) {      // TODO Auto-generated method stub
      Bundle extras = intent.getExtras();      FileLogUtil.e(TAG, "Service接收到WakeLock定时任务。");      PollService.startService(getApplicationContext());      FileLogUtil.e(TAG, "Service接收到WakeLock定时任务在定时任务中启动轮询Service。");      // Do the work that requires your app to keep the CPU running.
      // Release the wake lock provided by the WakefulBroadcastReceiver.
      //checkScreenOff();
      WakeCPUAlarmReceiver.completeWakefulIntent(intent);//释放wake
      WakeCPUAlarmReceiver.setCheckFlag(false);      WakeCPUAlarmReceiver mAlarmReceiver = new WakeCPUAlarmReceiver();
      mAlarmReceiver.startAlarm(WakecpuIntentService.this);      FileLogUtil.e(TAG, "Service释放wakelock后设置定时任务。");
}复制代码

service在后台也能够打印log  保持一直执行，最重要的是不耗电也不会卡机的问题。欢迎大家一起讨论学习。

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Dominic本尊44826 Android开发 @ 绿网天下