Flutter Chat App: Implementing Delivery Status Tracking

 To display a single grey tick in a chat application, you will need to implement a mechanism for tracking the delivery status of each message. This can be done by storing the delivery status of each message in the database (or a local cache) and updating it as the status changes.

For example, when a message is sent by the sender, you can store the initial delivery status as "pending" in the database. If the receiver is not logged in or their phone is closed, the message will remain in the pending state until the receiver logs in or opens their phone.

If the receiver has an internet connection, the message will be delivered to their device, and you can update the delivery status to "delivered" in the database. When the receiver reads the message, you can update the delivery status to "read".

To display the single grey tick, you can check the delivery status of each message in the chat screen and show the grey tick if the status is "pending" or "delivered". To do this, you can use a StreamBuilder widget to listen for updates to the delivery status of each message and update the UI accordingly.

Here is an example of how you can implement this:

// This is the database reference where you store the delivery status of each message. 
final db = FirebaseFirestore.instance; 
// This is the ID of the current user (the sender of the message). 
final userID = FirebaseAuth.instance.currentUser!.uid; 
// This is the ID of the receiver of the message.
final receiverID = 'RECEIVER_ID';

@override
Widget build(BuildContext context) { 
return 
Scaffold( 
body: Column(
      children: [ 
// Other chat UI components... 
// This is the StreamBuilder widget that listens for updates to the delivery status of each message. 
 StreamBuilder<QuerySnapshot>( 
stream: db.collection('messages')
              .where('sender', isEqualTo: userID) 
 .where('receiver', isEqualTo: receiverID) 
 .snapshots(), 
builder: (context, snapshot) { 
 if (!snapshot.hasData)
 {
              return Center(
                child: Text('No messages'),
 );
 } 
 return ListView.builder(
              itemCount: snapshot.data.length,
              itemBuilder: (context, index) { 
 DocumentSnapshot document = snapshot.data[index];
                String message = document['message'];
                String deliveryStatus = document['delivery_status']; 
 return ListTile(
                  // This is the message text.

                  title: Text(message),

                  // This is the delivery status icon (single grey tick). 
trailing: deliveryStatus == 'pending' || deliveryStatus == 'delivered'
                      ? Icon(Icons.check, color: Colors.grey)
                      : null,
                );
              },
            );
          },
        ),
      ],
    ),
  );
}

In the code above, the StreamBuilder widget listens for updates to the messages collection in the database where the sender is the current user and the receiver is the specified receiver. It then builds the chat UI by showing the message text and the delivery status icon for each message. The delivery status icon is shown as a single grey tick if the delivery status is "pending" or "delivered", and it is not shown if the