如何按最新消息对聊天列表进行排序？

Question

我不知道为什么我遇到了 chatList 没有按最后消息时间或最近消息排序的问题。我已尝试将 timestamp 存储在数据库中并使用 orderChildBy 时间戳，但它仍然无法正常工作。

这就是我在firebaseDatabase 中创建聊天列表的方式

    val timeAgo = Date().time

    val myTimeMap = HashMap<String, Any?>()
        myTimeMap["timestamp"] = timeAgo.toString()
        myTimeMap["id"] = friendId

    val friendTimeMap = HashMap<String, Any?>()
        friendTimeMap["timestamp"] = timeAgo.toString()
        friendTimeMap["id"] = currentUserID

    val chatListSenderReference = dbRef.child("ChatList").child(currentUserID).child(friendId)
        chatListSenderReference.keepSynced(true)
        chatListSenderReference.addListenerForSingleValueEvent(object : ValueEventListener{
              override fun onCancelled(p0: DatabaseError) {
              }
              override fun onDataChange(p0: DataSnapshot) {
                       if(!p0.exists()){
                             chatListSenderReference.updateChildren(friendTimeMap)
                       }
    val chatListReceiverReference = dbRef.child("ChatList").child(friendId).child(currentUserID)
        chatListReceiverReference.updateChildren(myTimeMap)
        }
    })

关于在 recyclerView 中检索聊天列表

 mUsers = ArrayList()
        val userRef = dbRef.child("ChatList").child(currentUserID).orderByChild("timestamp")
        userRef.addValueEventListener(object : ValueEventListener
        {
            override fun onCancelled(error: DatabaseError) {
            }

            override fun onDataChange(snapshot: DataSnapshot)
            {
                (mUsers as ArrayList).clear()
                snapshot.children.forEach {
                    val userUid = it.key
                    if (userUid != null) {
                        (mUsers as ArrayList).add(User(uid = userUid))
                    }
                }
                retrieveGroupChatList()
                chatListAdapter?.notifyDataSetChanged()
                chatListAdapter = context?.let { ChatListAdapter(it, (mUsers as ArrayList<User>), true) }
                recyclerViewChatList.adapter = chatListAdapter
            }
        })

这是数据库的图片，每次我发送或接收消息时时间戳都会更新。

Answer 1

你应该存储消息的时间戳，然后使用val chatListSenderReference = dbRef.child("ChatList").child(currentUserID).orderByChild("timestamp")

Answer 2

不确定这是否适用于您的情况，但对于我的聊天应用程序，我有一个消息列表，我所做的只是对列表进行排序

 //sort method - takes a list to be sorted
private fun sortMessagesByDate(messages: MutableList<Message>) {

    //sort messages by Date
    messages.sortWith(compareBy { it.timestamp })
}

联系人列表的循环方法

 // method for obtaining contacts and adding them to the lists
private fun getAllContacts() {
    val currentUserPhoneCredential = auth.currentUser?.phoneNumber!!

    firestore.collection("Contacts")
        .whereNotEqualTo("phoneNumber", currentUserPhoneCredential)
        .get().addOnSuccessListener { querySnapshot ->
        for (doc in querySnapshot) {

            val user = doc.toObject(User::class.java)
 //I have 2 lists one with just the names and another with the User Object
            contactsList.add(user)
            contactsNames.add(user.name!!)

        }
        adapter.notifyDataSetChanged()
    }

然后在 ListView 的 Adapter 上传入 Names List(contactsNames)

 adapter =
        ArrayAdapter(requireActivity(), android.R.layout.simple_list_item_1, contactsNames)

之后，当在特定位置单击名称时，应用程序导航到 DisplayMessage 片段，并获取与单击的联系人对应的 UserObject。

//implement listView onClick
    binding.listView.setOnItemClickListener { _, _, i, _ ->


       /*when a name is clicked on the ListView at a specific position the app navigates
        to the DisplayMessage Fragment taking a UserObject corresponding to the
         clicked contact.*/
        findNavController().navigate(ChatFragmentDirections
                                         .actionChatFragmentToMessageFragment(contactsList[i]))

    }

您还可以使用 RecyclerView 来显示联系人的姓名。