android - 如何在 Kotlin 中使用 Firebase 实时数据库的代码段中显示 RecyclerView

Question

我对从 Firebase 获取数据的 RecyclerView 有疑问。

我知道有很多类似的问题，但我找不到这个问题的正确解决方案。我想我有足够的代码来做属于的事情，但有些东西不起作用。当我打开我的应用程序时，我收到错误：

"E / RecyclerView: No adapter attached; skipping layout".

这是我的片段类：

class ExploreFragment : Fragment() {

    var fragmentView : View? = null
    var mSearchText : EditText? = null
    var mRecyclerView : RecyclerView? = null
    var mButton : ImageButton? = null

    var mDatabase : DatabaseReference? = null

    var FirebaseRecyclerAdapter : FirebaseRecyclerAdapter<Users1 , UsersViewHolder>? = null

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?


    ): View? {

        fragmentView = LayoutInflater.from(activity).inflate(R.layout.fragment_explore, container, false)

        mSearchText = view?.findViewById(R.id.search_edit_text)

        mButton = view?.findViewById(R.id.search_btn)

        mRecyclerView = view?.findViewById(R.id.recycler_view_search)
        mRecyclerView?.setHasFixedSize(true)
        mRecyclerView?.layoutManager = LinearLayoutManager(context)

        mDatabase = FirebaseDatabase.getInstance().getReference("Users")



        mSearchText?.addTextChangedListener(object  : TextWatcher {
            override fun afterTextChanged(p0: Editable?) {

            }

            override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
            }

            override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {

                val searchText = mSearchText?.getText().toString().trim()

                loadFirebaseData(searchText)
            }
        } )


        return fragmentView
    }

    private fun loadFirebaseData(searchText : String) {

        if(searchText.isEmpty()){

            FirebaseRecyclerAdapter?.cleanup()
            mRecyclerView?.adapter = FirebaseRecyclerAdapter

        }else {


            val firebaseSearchQuery = mDatabase?.orderByChild("username")?.startAt(searchText)?.endAt(searchText + "\uf8ff")

            FirebaseRecyclerAdapter = object : FirebaseRecyclerAdapter<Users1, UsersViewHolder>(

                Users1::class.java,
                R.layout.layout_list,
                UsersViewHolder::class.java,
                firebaseSearchQuery
            ){
                override fun populateViewHolder(viewHolder: UsersViewHolder, model: Users1?, position: Int) {

                    viewHolder.mview.userName.setText(model?.name)

                }

            }

            mRecyclerView?.adapter = FirebaseRecyclerAdapter

        }
    }

companion object {
       @JvmStatic
        fun newInstance() =
            ExploreFragment().apply {
                arguments = Bundle().apply {}
            }
    }
    class UsersViewHolder(var mview : View) : RecyclerView.ViewHolder(mview) {

    }
}

这是我的布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">



    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/app_bar_layout_search">

        <androidx.appcompat.widget.Toolbar
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_marginTop="4dp"
            android:layout_marginLeft="6dp"
            android:layout_marginRight="6dp"
            android:background="@android:color/white"
            android:id="@+id/search_toolbar">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent">


                <EditText
                    android:id="@+id/search_edit_text"
                    android:layout_width="297dp"
                    android:layout_height="45dp"
                    android:layout_marginTop="5dp"
                    android:layout_marginEnd="13dp"
                    android:layout_marginRight="60dp"
                    android:layout_toStartOf="@+id/search_btn"
                    android:background="@drawable/search_layout"
                    android:ems="20"
                    android:hint="Search here"
                    android:inputType="textPersonName"
                    android:paddingLeft="20dp"
                    android:paddingTop="10dp"
                    android:paddingRight="20dp"
                    android:paddingBottom="10dp"
                    android:textColor="#999999"
                    android:textSize="10sp" />

                <ImageButton
                    android:id="@+id/search_btn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignTop="@+id/search_edit_text"
                    android:layout_alignBottom="@+id/search_edit_text"
                    android:layout_alignParentEnd="true"
                    android:layout_marginTop="0dp"
                    android:layout_marginEnd="34dp"
                    android:layout_marginRight="30dp"
                    android:layout_marginBottom="-1dp"
                    android:background="@android:color/background_light"
                    app:srcCompat="@mipmap/search_button" />


            </RelativeLayout>

        </androidx.appcompat.widget.Toolbar>

    </com.google.android.material.appbar.AppBarLayout>

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPagerImageSlider"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingStart="80dp"
        android:paddingEnd="80dp" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view_search"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/app_bar_layout_search">

    </androidx.recyclerview.widget.RecyclerView>

</RelativeLayout>

这是我的 Users1 类：

class Users1 {
    var name: String? = null
    var image: String? = null

    constructor() {}

    constructor(name: String?, image: String?) {
        this.name = name
        this.image = image
    }
}

标签： androidfirebasekotlinfirebase-realtime-databaseandroid-recyclerview