android - 在recyclerview kotlin中插入firebase快照

Question

我有一个简单的回收器视图，它从数据库中读取列表，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

下面的函数在包含回收器视图的 xml 布局的 kotlin 片段类中

 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，可以按要求提供，但我感觉那里的代码是正确的

• UserInfo.Uids是数据类，包含name和email

• adapter变量在之前声明override fun onCreateView

标签： androidkotlinfirebase-realtime-databaseandroid-recyclerviewdata-class

Answer 1

看起来你没有用任何数据填充 recyclerview。适配器总是用空初始化ArrayList：

                                    /* 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()