title: How to know which item the user is looking at in a list Flutter
body: <p>I use in my application a list of posts, I would like to know on which item is the user to update a boolean of the post posts.hasBeenSeen = true.</p>
  <pre><code>List&lt;PostModel&gt; posts = snapshot.data.cast&lt;PostModel&gt;();
      return ListView.builder(
        itemCount: posts.length,
        itemBuilder: (context, index)
        {
          return ChangeNotifierProvider.value(
              value: posts[index],
              child: PostItem(postModel: posts[index]));
        },
      );
  </code></pre>
  <p><a href="https://i.stack.imgur.com/vKoxh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vKoxh.png" alt="enter image description here" /></a></p>
  <p>Here for example I want that the boolean is true only for the post 1, because the post 2 has not been seen yet.</p>