如何使我的recyclerview正确显示我从Retrofit接收的数据？

问题描述

从改造中获取数据，但不会显示在屏幕上。

过去几天我一直在学习实时数据和改造，我正在尽力将其与recyclerview结合使用，但是我在MainActivity.kt中弄乱了地方。我已经花了几个小时尝试自己获取它，但是我还没有找到解决我特定问题的方法。我相信我的错误可能出在代码的Lateinit部分，还是我的initRecyclerView函数。

MainActivity.kt

txt = u"565543" 

x = txt.isnumeric()

print(x)

AlbumsAdapter.kt

package com.dev20.retrofitpractice


import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
import androidx.lifecycle.liveData
import androidx.recyclerview.widget.LinearLayoutManager
import kotlinx.android.synthetic.main.activity_main.*
import retrofit2.Response


class MainActivity : AppCompatActivity() {

    private lateinit var albumsAdapter: AlbumsAdapter


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

        val list = ArrayList<AlbumsItem>()


        initRecyclerView()
        getData()
        albumsAdapter = AlbumsAdapter(list)
    }
        private fun getData() {
            val retService: AlbumService = RetrofitInstance
                .getRetrofitInstance()
                .create(AlbumService::class.java)
            val responseLiveData: LiveData<Response<Albums>> = liveData {
                val response = retService.getAlbums()
                emit(response)
            }

            responseLiveData.observe(this,Observer {
                val albumsList: MutableListIterator<AlbumsItem>? = it.body()?.listIterator()
                if (albumsList != null) {
                    while (albumsList.hasNext()) {
                        val albumsItem: AlbumsItem = albumsList.next()
                        Log.i("MYTAG",albumsItem.title)

                    }

                }
            })
        }

    private fun initRecyclerView() {

        recycler_view.apply {
            layoutManager = LinearLayoutManager(this@MainActivity)
            adapter = albumsAdapter
        }
    }
}

Albums.kt

package com.dev20.retrofitpractice

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.albums_list.view.*


class AlbumsAdapter(private val albumsList: List<AlbumsItem>) : RecyclerView.Adapter<AlbumsAdapter.AlbumsViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup,viewType: Int): AlbumsViewHolder {
        val itemView = LayoutInflater.from(parent.context).inflate(R.layout.albums_list,parent,false)

        return AlbumsViewHolder(itemView)
    }

    override fun onBindViewHolder(holder: AlbumsViewHolder,position: Int) {
        val currentItem = albumsList[position]

        holder.textViewAlbums.text = currentItem.title
    }

    override fun getItemCount() = albumsList.size

    class AlbumsViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val textViewAlbums: TextView = itemView.text_view_albums
    }
}

AlbumsItem.kt

package com.dev20.retrofitpractice

class Albums : ArrayList<AlbumsItem>()

AlbumService.kt

package com.dev20.retrofitpractice


import com.google.gson.annotations.SerializedName

data class AlbumsItem(
    @SerializedName("id")
    val id: Int,@SerializedName("title")
    val title: String,@SerializedName("userId")
    val userId: Int
)

activity_main.xml

package com.dev20.retrofitpractice

import retrofit2.Response
import retrofit2.http.GET

interface AlbumService {

    //define abstract function to get albums data
    //returns retrofit response of type Albums
    //Use suspend modifier because we are using coroutines with retrofit
    @GET("/albums")
    suspend fun getAlbums() :Response<Albums>
}

ablums_list.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:padding="4dp"
        android:clipToPadding="false"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:listitem="@layout/albums_list"/>


</androidx.constraintlayout.widget.ConstraintLayout>

解决方法

MainActivity oncreate添加：

albumsAdapter = AlbumAdapter(albumList)

,

您的适配器未初始化。尝试初始化它。并请注意，通过构造函数传递列表不是最佳方法。假设您有一个要更新的列表，是否每次都要对适配器进行初始化？没有！因此，您应该做的是创建一个单独的方法来将列表设置为Adapter。

更新

您要为适配器设置一个空列表，然后将列表传递给适配器。所以像这样安排您的代码：-

initRecyclerView()
getData()
albumsAdapter = AlbumsAdapter(list)