如何在recyclerview中显示嵌套的子数据

Question

我想在 recyclerview 中显示项目节点详细信息，但出现了一些错误。我尝试了很多方法，但是我没有在数据库引用中的项目节点中获得项目的 uid。我正在尝试在 firebase 数据库参考中获取项目 uid，但无法做到。如何获取项目 uid 数据库参考对象

mainactivity code


class MainActivity : AppCompatActivity() {

lateinit var recyclerView: RecyclerView

lateinit var layoutManager: RecyclerView.LayoutManager

lateinit var RecyclerAdapter: RecyclerAdapter
lateinit var databaseReference: DatabaseReference
var database: FirebaseDatabase? = null

lateinit var auth:FirebaseAuth

    var personlist = arrayListOf<Persons>()


 override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)


    recyclerView = findViewById(R.id.recyclerpersonview)



    database = FirebaseDatabase.getInstance()
    auth = FirebaseAuth.getInstance()

     





 databaseReference=database?.reference!!.child("Users")
.child(auth.currentUser!!.uid).child("items")

                                                                             
    databaseReference.addValueEventListener(object 
:ValueEventListener{

        override fun onDataChange(snapshot: DataSnapshot) {
            try {

                for (items in snapshot.children) {
                    val item1 = items.getValue(Persons::class.java)
                    personlist.add(item1!!)
                }

            }catch (e:Exception){
                
    
  
 
 
    
Toast.makeText(this@MainActivity,e.message,Toast.LENGTH_SHORT).show()
            }

        }
        override fun onCancelled(error: DatabaseError) {
            Toast.makeText(this@MainActivity,"unable to load 
    data",Toast.LENGTH_SHORT).show()
        }


    })

    layoutManager = LinearLayoutManager(this)

    RecyclerAdapter = RecyclerAdapter(this, personlist)

    RecyclerAdapter.notifyDataSetChanged()

    recyclerView.adapter = RecyclerAdapter

    recyclerView.layoutManager = layoutManager

   }

  recycleradapter code


 class RecyclerAdapter(var context: MainActivity, var personlist: 
  ArrayList<Persons>) :
 RecyclerView.Adapter<RecyclerAdapter.Personviewholder>() {
 override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): 
 Personviewholder {
    val view = 
 LayoutInflater.from(parent.context).inflate(R.layout.singlerow, 
parent, 
  false)

    return Personviewholder(view)
}

override fun getItemCount(): Int {
    return personlist.size
}

override fun onBindViewHolder(holder: Personviewholder, position: 
Int) {
    val view = personlist[position]
    holder.personname.text = view.personname
    holder.persondesc.text = view.persondesc
    
Picasso.with(context).load(view.personimage).into(holder.personimg)

    holder.layoutlist.setOnClickListener {
        val intent = Intent(context, Additem::class.java)
        context.startActivity(intent)

    }

}


inner class Personviewholder(view: View) : 
RecyclerView.ViewHolder(view) 
 {
    var personname: TextView = view.findViewById(R.id.tvname)
    var persondesc: TextView = view.findViewById(R.id.tvpersondesc)
    var personimg: ImageView = view.findViewById(R.id.imgperson)
    var layoutlist: LinearLayout = 
 view.findViewById(R.id.linearlayoutlist)
 }
 }

data class
data class Persons( var personname:String,
                var persondesc:String,
                var personimage:String)   


debug information
06/21 22:05:29: Launching 'app' on Pixel 3 API 30.
$ adb shell am start -n 
"com.a.recyclerview/com.a.recyclerview.LoginActivity" -a 
android.intent.action.MAIN -c android.intent.category.LAUNCHER -D
Waiting for application to come online: com.a.recyclerview | 
com.a.recyclerview.test
Waiting for application to come online: com.a.recyclerview | 
com.a.recyclerview.test
Connecting to com.a.recyclerview
Capturing and displaying logcat messages from application. This 
behavior can be disabled in the "Logcat output" section of the 
"Debugger" settings page.
I/System.out: Debugger has connected
waiting for debugger to settle...
Connected to the target VM, address: 'localhost:8602', transport: 
'socket'
I/chatty: uid=10155(com.a.recyclerview) identical 6 lines
I/System.out: waiting for debugger to settle...
I/System.out: debugger has settled (1337)
D/NetworkSecurityConfig: No Network Security Config specified, using 
 platform default
D/NetworkSecurityConfig: No Network Security Config specified, using 
platform default

I/FirebaseApp：设备解锁：为应用初始化所有 Firebase API [默认] I/FirebaseAuth: [FirebaseAuth:] 准备创建服务 与回退实现的连接 D/FirebaseAuth：通知 id 令牌侦听器有关用户（ rwy6MpJLxYWyIAQbj2xFR0sRaRw2）。 I/FirebaseInitProvider：FirebaseApp 初始化成功 D/libEGL：加载/vendor/lib/egl/libEGL_emulation.so D/libEGL：加载 /vendor/lib/egl/libGLESv1_CM_emulation.so I/DynamiteModule：考虑本地模块 com.google.android.gms.measurement.dynamite:51 和远程模块 com.google.android.gms.measurement.dynamite:51 选择的远程版本 com.google.android.gms.measurement.dynamite，版本 >= 51 V/DynamiteModule: Dynamite loader version >= 2, using loadModule2NoCrashUtils D/libEGL：加载 /vendor/lib/egl/libGLESv2_emulation.so W/.a.recyclervie: 访问隐藏方法 Landroid/view/View;- > computeFitSystemWindows(Landroid/graphics/Rt;Landroid/graphics /矩形;)Z

(greylist, reflection, allowed)
Accessing hidden method Landroid/view/ViewGroup;- 

makeOptionalFitsSystemWindows()V（灰名单，反射，允许） V/FA: onActivityCreated W/.a.recyclervie: 验证 android.content.pm.ApplicationInfo cn.a(java.lang.String, int) 耗时 170.667ms (64.45 bytecodes/s) (984B 近似峰值分配） V/FA：启用应用测量收集 V/FA：为应用程序包启用应用程序测量，谷歌应用程序 ID： com.a.recyclerview, 1:14819963865:android:0fbd8c80422b89f216dfc8 I/FA：应用测量已初始化，版本：42020 启用调试日志运行： adb shell setprop log.tag.FA VERBOSE I/FA：要启用更快的调试模式事件日志记录，请运行： adb shell setprop debug.firebase.analytics.app com.a.recyclerview D/FA：启用调试级消息记录 V/FA: onActivityCreated V/FA：连接到远程服务 D/HostConnection: HostConnection::get() 新主机连接 建立 0xf580da60, tid 7482 D/HostConnection：HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data GL_OES_EGL_image_external_essl3 GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_3_0 W/OpenGLRenderer：无法选择配置 EGL_SWAP_BEHAVIOR_PRESERVED，重试不... D/EGL_emulation：eglCreateContext：0xf580cb80：maj 3 min 0 rcv 3 D/EGL_emulation: eglMakeCurrent: 0xf580cb80: ver 3 0 (tinfo 0xc53c7b90) (第一次) V/FA：连接尝试已在进行中 I/Gralloc4：不支持映射器 4.x D/HostConnection: createUnique: 调用 D/HostConnection: HostConnection::get() 新主机连接 建立 0xf580dc20, tid 7482 D/goldfish-address-space: allocate: 请求大小为 0x100 的块 allocate: ioctl allocate 返回的偏移量 0x3fbc4d000 大小 0x2000 V/FA：连接尝试已在进行中 V/FA：活动恢复，时间：3149571 D/HostConnection：HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data GL_OES_EGL_image_external_essl3 GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_3_0 I/FA：未找到跟踪代码管理器，因此不会使用 V/FA：连接尝试已在进行中 V/FA：连接尝试已在进行中 I/OpenGLRenderer：戴维！持续时间=757ms；标志=1， 预期Vsync=3149655912401，Vsync=3149722579065， 最旧输入事件=9223372036854775807，最新输入事件=0， HandleInputStart=3149736734700, AnimationStart=3149737212900, PerformTraversalsStart=3149737532500，DrawStart=3150142325100， SyncQueued=3150160621300，SyncStart=3150229754900， IssueDrawCommandsStart=3150230091100，SwapBuffers=3150464728600， FrameCompleted=3150482529700, DequeueBufferDuration=422700, QueueBufferDuration=1357200, GpuCompleted=72904454231491230, D/FA：连接到远程服务 V/FA：处理排队服务任务：5 I/.a.recyclervie: WaitForGcToComplete 阻塞了 RunEmptyCheckpoint ProfileSaver 为 5.416 毫秒 D/CompatibilityChangeReporter：Compat change id 报告：147798919； 用户标识符 10155;状态：启用 V/FA：不活动，与服务断开连接

![](https://i.stack.imgur.com/WR6Pd.png)

Answer 1

您收到了两次child("items")，因此最终尝试读取不存在数据的/Users/$uid/items/items。

要解决此问题，只需指定一次child("items")：

databaseReference = 
database?.reference!!.child("Users").child(auth.currentUser!!.uid).child("items")

databaseReference.addValueEventListener(object :ValueEventListener{
  ...