Android push Wake up screen

how does Android implement the push Wake up screen?
my phone has set up a rear lock screen to receive push messages, but the code that has been added to the wake-up screen is as follows, and there is no response on the screen 

 <uses-permission android:name="android.permission.WAKE_LOCK" />

   PowerManager powerManager = (PowerManager) getSystemService(POWER_SERVICE);
   WakeLock wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "MyWakelockTag");
   wakeLock.acquire();
   wakelock.release();

what is the reason?

Android
Mar.24,2021

https://blog.csdn.net/xinpeng.

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