title: How to get all child's data in firebase and show it into my android app?
body: <p>I have this structure in my Firebase Real-time database :</p>
  
  <p><img src="https://i.stack.imgur.com/oCubR.png" alt="enter image description here"></p>
  
  <p>How can I count the data and show it in my app, which listener shall I use to get all childrens? </p>