试图在Kotlin中创建一个简单的recyclerView,但是适配器没有正确应用

Question

我正在尝试在Kotlin中使用我通过Volley获得的数据创建一个简单的recyclerView(我已经确认返回了正确的数据),我一直在运行错误E/RecyclerView: No adapter attached; skipping layout,实际上我已经指定了一个带有我自定义适配器类的适配器创建:

class ImageAdapter(var c: Context, var list: ArrayList<Image>) : RecyclerView.Adapter<ImageAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder? {
    val layoutInflater = LayoutInflater.from(parent.context)
    return ViewHolder(layoutInflater.inflate(R.layout.image_cardview, parent, false))
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    val imageUrl = list[position].url
    val submitter = list[position].submitter
    val color = list[position].color
    holder.submitterTV.text = submitter
    holder.card.setCardBackgroundColor(Color.parseColor(color))
}

override fun getItemCount() = list.size
class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView){
    val card = itemView.card
    val submitterTV = itemView.submitter
    val imageView = itemView.image
}

}

这是我的MainActivty类,我在其中实际调用JSON并尝试将我的适配器与我创建的ArrayList连接:

class MainActivity : AppCompatActivity() {
val images = ArrayList<Image>()
override fun onCreate(savedInstanceState: Bundle?) {

    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    imageList.layoutManager = LinearLayoutManager(applicationContext)
    request("https://api.unsplash.com/photos/curated/?client_id=API_KEY")
    imageList.adapter = ImageAdapter(applicationContext, images)

}

private fun request(url: String) {
    val queue = Volley.newRequestQueue(this)
    val stringRequest = JsonArrayRequest(url, Response.Listener<JSONArray> { response ->
        try {
            for (i in 0..(response.length() - 1)) {
                val image: Image = Image(response.getJSONObject(i).getJSONObject("urls").getString("full"), response.getJSONObject(i).getJSONObject("user").getString("username"), response.getJSONObject(i).getString("color"))
                images.add(image)
            }

            imageList.adapter.notifyDataSetChanged()

        } catch (e: JSONException) {
            e.printStackTrace()
        }
    }, Response.ErrorListener { })
    queue.add(stringRequest)
}
}

我创建了一个自定义数据类Image,它存储三个字段:imageUrl,submitter和color,所有这些都是从JSON派生的.我认为notifyDataSetChanged()在请求完成后调用我的适配器将允许recyclerView更新并显示项目,但屏幕上根本没有显示任何内容.有没有人知道我搞砸了哪里？

Answer 1

你可以从这里下载源代码(Recyclerview In Kotlin Android)

MainActivity.kt:

package com.deepshikha.recyclerviewkotlin
import android.app.Activity
import android.os.Bundle
import android.support.v7.widget.LinearLayoutManager
import android.view.Window
import android.view.WindowManager
import android.widget.LinearLayout
import kotlinx.android.synthetic.main.activity_main.*
import net.simplifiedcoding.recyclerviewexample.CustomAdapter

class MainActivity : Activity() {


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        requestWindowFeature(Window.FEATURE_NO_TITLE)
        window.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN)

        setContentView(R.layout.activity_main)

        val users = ArrayList<Model_Details>()
        users.add(Model_Details("Kaju katli", "Kaju katli, also known as kaju Katari or kaju barfi, is an Indian dessert similar to a barfi.",R.drawable.kaju))
        users.add(Model_Details("Doughnut", "The doughnut is popular in many countries and prepared in various forms as a sweet snack that can be homemade or purchased in bakeries, supermarkets, food stalls, and franchised specialty outlets",R.drawable.donuts))
        users.add(Model_Details("Panna cotta", "Panna cotta is an Italian dessert of sweetened cream thickened with gelatin and molded. The cream may be aromatized with rum, coffee, vanilla, or other flavorings.",R.drawable.panna_cotta))
        users.add(Model_Details("Rose Cookies", "Rose cooky is a famous South Indian snack made during festivals",R.drawable.rosecookies))
        users.add(Model_Details("Belgian waffle", "In North America, Belgian waffles are a variety of waffle with a lighter batter, larger squares, and deeper pockets than ordinary American waffles",R.drawable.belgianwaffle))

        val obj_adapter = CustomAdapter(users)

        recyclerView.layoutManager = LinearLayoutManager(this, LinearLayout.VERTICAL, false)
        recyclerView.adapter = obj_adapter
    }


}

CustomAdapter.kt:

package net.simplifiedcoding.recyclerviewexample

import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import com.deepshikha.recyclerviewkotlin.Model_Details
import com.deepshikha.recyclerviewkotlin.R
import kotlinx.android.synthetic.main.adapter_details.view.*

class CustomAdapter(val userList: ArrayList<Model_Details>) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {

    //this method is returning the view for each item in the list
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CustomAdapter.ViewHolder {
        val v = LayoutInflater.from(parent.context).inflate(R.layout.adapter_details, parent, false)
        return ViewHolder(v)
    }

    //this method is binding the data on the list
    override fun onBindViewHolder(holder: CustomAdapter.ViewHolder, position: Int) {
        holder.bindItems(userList[position])
    }

    //this method is giving the size of the list
    override fun getItemCount(): Int {
        return userList.size
    }

    //the class is hodling the list view
    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

        fun bindItems(user: Model_Details) {
            itemView.tv_name.text=user.name
            itemView.tv_des.text=user.des
            itemView.iv_name.setImageResource(user.image)

        }
    }

}

谢谢!

Answer 2

看下面的例子，我想你可以给你一个想法。

您可以从这里获取示例：https : //github.com/Siddharha/RecyclerviewTest_Kotlin

主要活动

class MainActivity : AppCompatActivity() {
private var myAdapter: MyAdapter? = null
private var arrayList: ArrayList<MyItem>? = null
private var layoutManager: RecyclerView.LayoutManager? = null
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    initialize()
    setupList()
    loaddata()
}

private fun loaddata() {

    for (i in 0..9) {
        val myItem = MyItem()
        myItem.name = "Sid_" + i
        myItem.number = "098899876" + i
        arrayList!!.add(myItem)
    }

    myAdapter!!.notifyDataSetChanged()

}

private fun setupList() {
    rlItems!!.layoutManager = layoutManager
    rlItems!!.adapter = myAdapter
}

private fun initialize() {
    arrayList = ArrayList<MyItem>()
    layoutManager = LinearLayoutManager(this, LinearLayout.VERTICAL, false)
    myAdapter = MyAdapter(arrayList!!, this, R.layout.item_cell)

  }
}

转接器类别

internal class MyAdapter(private val arrayList: ArrayList<MyItem>,
                     private val context: Context,
                     private val layout: Int) : RecyclerView.Adapter<MyAdapter.ViewHolder>() {


override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyAdapter.ViewHolder {
    val v = LayoutInflater.from(parent.context).inflate(layout, parent, false)
    return ViewHolder(v)
}

override fun onBindViewHolder(holder: MyAdapter.ViewHolder, position: Int) {
    holder.bindItems(arrayList[position])
}

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

internal inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

    fun bindItems(items: MyItem) {
        itemView.tvName.text = items.name
        itemView.tvNumber.text = items.number
    }
  }
}

物品类别

internal class MyItem {
var name: String? = null
var number: String? = null
}