title: How to keep Android service alive when screen off and home pressed?
body: <p>I want to know how to let my android service is always running when screen off?</p>
  <p>of course , I set WakeLock , but it's seems not working when screen off ....</p>
  <p>and at the same time , my app is in background(home pressed)</p>
  <p>I try to use notificationManager, yes, it's working even screen off,</p>
  <p>but if I want to send data(json) to my web server , it's not working,</p>
  <p>does any suggestion? By the way , android sdk is 30, Thanks.</p>