xamarin/xamarin.forms 在锁屏电源唤醒时保持后台运行

PARTIAL_WAKE_LOCK:保持CPU 运转，屏幕和键盘灯有可能是关闭的。
SCREEN_DIM_WAKE_LOCK：保持CPU 运转，允许保持屏幕显示但有可能是灰的，允许关闭键盘灯
SCREEN_BRIGHT_WAKE_LOCK：保持CPU 运转，允许保持屏幕高亮显示，允许关闭键盘灯
FULL_WAKE_LOCK：保持CPU 运转，保持屏幕高亮显示，键盘灯也保持亮度
ACQUIRE_CAUSES_WAKEUP：强制使屏幕亮起，这种锁主要针对一些必须通知用户的操作.
ON_AFTER_RELEASE：当锁被释放时，保持屏幕亮起一段时间**

方法（一）

 1 [BroadcastReceiver(Enabled = true)]
 2     public class AlarmService : BroadcastReceiver
 3     {
 4         //public event EventHandler WakeLockStatusChanged;
 5         public override void OnReceive(Context context, Intent intent)
 6         {
 7             PowerManager pm = (PowerManager)context.GetSystemService(Context.PowerService);
 8             PowerManager.WakeLock wl = pm.NewWakeLock(WakeLockFlags.Partial, "MyWakelockTag");
 9             wl.Acquire();
10             //if (wl.IsHeld)
11             //{
12             //    wl.Release();
13             //}
14         }
15     }

 1  private void InitBroadcastReceiver()
 2         {
 3             _alarmService = new AlarmService();
 4             Application.Context.RegisterReceiver(_alarmService, new IntentFilter(ConnectivityManager.ConnectivityAction));
 5         }
 6 
 7  protected override void OnStart()
 8         {
 9             base.OnStart();
10             InitBroadcastReceiver();
11         }
12 
13         protected override void OnStop()
14         {
15             base.OnStop();
16 
17             if (_alarmService != null)
18             {
19                 Application.Context.UnregisterReceiver(_alarmService);
20                 _alarmService = null;
21             }
22 
23         }

方法（二）

 1    //获取电源锁，保持该服务在屏幕熄灭时仍然获取CPU时，保持运行  
 2         private void AcquireWakeLock()
 3         {
 4             if (null == _wakeLock)
 5             {
 6                 PowerManager pm = (PowerManager)GetSystemService(Context.PowerService);
 7                 _wakeLock = pm.NewWakeLock(WakeLockFlags.Partial | WakeLockFlags.OnAfterRelease, "MyWakelockTag");
 8                 if (_wakeLock != null)
 9                 {
10                     _wakeLock.Acquire();
11                 }
12             }
13         }
14 
15         //释放设备电源锁  
16         private void ReleaseWakeLock()
17         {
18             if (null != _wakeLock || _wakeLock.IsHeld)
19             {
20                 _wakeLock.Release();
21                 _wakeLock = null;
22             }
23         }

参考资料：
https://docs.microsoft.com/zh-cn/dotnet/api/Android.OS.PowerManager.NewWakeLock?view=xamarin-android-sdk-9#Android_OS_PowerManager_NewWakeLock_Android_OS_WakeLockFlags_System_String_

https://stackoverflow.com/questions/54532221/prevent-app-from-going-on-onpause-when-turning-screen-off-using-partial-wakelock/54548392?r=SearchResults#54548392

http://www.itgo.me/a/x9010099145016859770/xamarin-forms-broadcast-receiver-not-working-when-app-is-closed

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原文地址：https://www.cnblogs.com/mschen/p/11294665.html