在recyclerview kotlin中插入firebase快照

Posted 2023-04-19

【中文标题】在recyclerview kotlin中插入firebase快照

【英文标题】：inserting firebase snapshot in recyclerview kotlin

【发布时间】：2021-06-16 08:36:17

【问题描述】：

我有一个简单的回收器视图，它从数据库中读取一个列表，当我将它们记录到控制台时我可以看到数据，但它没有显示在回收器视图中

下面的函数在 kotlin 片段类中，用于包含回收器视图的 xml 布局

 override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?,
    ): View? 
        // Inflate the layout for this fragment
        val view: View = inflater.inflate(R.layout.fragment_chat_list, container, false)


        view.recyclerView?.setHasFixedSize(true)
        view.recyclerView?.layoutManager = LinearLayoutManager(context)




        ref?.addChildEventListener(object : ChildEventListener 
            override fun onChildAdded(snapshot: DataSnapshot, previousChildName: String?) 
                val bal = snapshot.getValue<UserInfo.Uids>()

                if (bal != null) 
                 UserInfo.Uids(bal.email,bal.uid,bal.displayName)         
               
                Log.d("RecyclerView",  UserInfo.Uids().toString())
                Log.d("RecyclerView", bal.toString())
                adapter = BalAdapter(requireContext(),  ArrayList<UserInfo.Uids>(),  R.layout.users)
                adapter!!.notifyDataSetChanged()
            

            override fun onChildChanged(snapshot: DataSnapshot, previousChildName: String?) 
                TODO("Not yet implemented")
            

                override fun onChildRemoved(snapshot: DataSnapshot) 
                TODO("Not yet implemented")
            

            override fun onChildMoved(snapshot: DataSnapshot, previousChildName: String?) 
                TODO("Not yet implemented")
            

            override fun onCancelled(p0: DatabaseError) 
                TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
            




        )
      
        return  view

    

R.layout.fragment_chat_list是包含recycler view标签的xml

R.layout.users是数据xml

view.recyclerView 是回收站视图标签

BalAdapter是适配器类，可按要求提供，但我觉得那里的代码是正确的

UserInfo.Uids为数据类，包含name和email

adapter 变量在 override fun onCreateView 之前声明

【参考方案1】：

看起来您没有在 recyclerview 中填充任何数据。适配器总是用空的ArrayList初始化：

                                    /* This is an empty ArrayList */
adapter = BalAdapter(requireContext(),  ArrayList<UserInfo.Uids>(),  R.layout.users)

您需要将从 firebase 读取的值添加到数组列表中，然后将该数组列表传递给适配器

例如：

//Before any firebase requests:
val balList = ArrayList<UserInfo.Uids>()
adapter = BalAdapter(requireContext(), balList,  R.layout.users)

...

//After you get data from firebase
val bal = snapshot.getValue<UserInfo.Uids>()
balList.add(bal)
adapter.notifyDataSetChanged()