title: how to implement message seen feature in Firebase chat app
body: <p>I'm developing <code>firebase</code> chat app.I want to include <code>seen</code> feature init just like <strong>whatsapp</strong> . I have  referred this <a href="https://stackoverflow.com/questions/44614301/implement-a-read-receipt-feature-in-firebase-group-messaging-app">question</a> to build database.</p>
  
  <p>I'm using <code>addChildEventListener</code> to fetch data from <code>firebase</code>.And this is my app <a href="https://i.stack.imgur.com/4BgL4.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4BgL4.jpg" alt="enter image description here"></a>  every thing works fine.</p>
  
  <p>I don't know how to achieve this feature because we don't have any control like <code>click event</code> on messages.</p>
  
  <p>Thank you in Advance.</p>
  
  <p>` </p>