[在此处输入图像描述][1]
尽管代码的格式和实现都很好，但应用程序中似乎存在一个错误，不允许应用程序检索和显示数据。用于构建RecyclerView:的后端完整组件
显示RecyclerView:的碎片
package com.reazon.foodrunner.fragment
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.firebase.ui.database.FirebaseRecyclerAdapter
import com.google.firebase.database.*
import com.reazon.foodrunner.R
import com.reazon.foodrunner.adapter.HomeRecyclerAdapter
import com.reazon.foodrunner.model.Restaurants
class HomeFragment : Fragment() {
private var mDatabaseReference: DatabaseReference? = null
private var recyclerAdapter: HomeRecyclerAdapter? = null
private var recyclerHome: RecyclerView? = null
internal var restaurantsList: MutableList<Restaurants> = ArrayList()
private var layoutManager: RecyclerView.LayoutManager? = null
private lateinit var adapter: FirebaseRecyclerAdapter<Restaurants,HomeRecyclerAdapter.HomeRecyclerViewHolder>
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
val view = inflater.inflate(R.layout.fragment_home, container, false)
mDatabaseReference = FirebaseDatabase.getInstance().getReference("Restaurants")
recyclerHome = view.findViewById(R.id.recyclerHomeAll)
layoutManager = LinearLayoutManager(activity)
recyclerHome!!.layoutManager = layoutManager
//retrieve data from firebase
retrieveAllRestaurants()
return view
}
private fun retrieveAllRestaurants() {
restaurantsList.clear()
val restaurantReference = FirebaseDatabase.getInstance().reference.child("Restaurants")
restaurantReference.addValueEventListener(object : ValueEventListener {
override fun onCancelled(error: DatabaseError) {
Log.d("ERROR ", "" + error.message)
}
override fun onDataChange(p0: DataSnapshot) {
for (snapshot in p0.children) {
val restaurant = snapshot.getValue(Restaurants::class.java)
restaurant!!.getRestaurant()
restaurant.getRestaurantRating()
restaurant.getCostForOne()
restaurant.getRestaurantName()
restaurantsList.add(restaurant)
}
recyclerAdapter = HomeRecyclerAdapter(context!! , restaurantsList)
recyclerHome?.adapter = recyclerAdapter
}
})
}
}
使用的模型类：-
型号类别
package com.reazon.foodrunner.model
class Restaurants {
private var id: String? = null
private var name: String? = null
private var rating: String? = null
private var cost_for_one: String? = null
private var imageUrl: String? = null
constructor()
constructor(
id: String,
name: String,
rating: String,
cost_for_one: String,
imageUrl: String
) {
this.id = id
this.name = name
this.rating = rating
this.cost_for_one = cost_for_one
this.imageUrl = imageUrl
}
fun getRestaurant(): String? {
return imageUrl
}
fun setRestaurant(imageUrl: String){
this.imageUrl = imageUrl
}
fun getRestaurantId(): String? {
return id
}
fun setRestaurantId(id: String){
this.id = id
}
fun getRestaurantName(): String? {
return name
}
fun setRestaurantName(name: String){
this.name = name
}
fun getRestaurantRating(): String? {
return rating
}
fun setRestaurantRating(rating: String){
this.rating = rating
}
fun getCostForOne(): String? {
return cost_for_one
}
fun setCostForOne(cost_for_one: String) {
this.cost_for_one = cost_for_one
}
}
使用的适配器类：-
适配器类
package com.reazon.foodrunner.adapter
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageButton
import android.widget.ImageView
import android.widget.TextView
import android.widget.Toast
import androidx.recyclerview.widget.RecyclerView
import com.reazon.foodrunner.R
import com.reazon.foodrunner.model.Restaurants
import com.squareup.picasso.Picasso
class HomeRecyclerAdapter(
var context: Context,
var restaurantsList: List<Restaurants>
) : RecyclerView.Adapter<HomeRecyclerAdapter.HomeRecyclerViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): HomeRecyclerViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.recycler_home_single_row, parent, false)
return HomeRecyclerViewHolder(view)
}
override fun getItemCount(): Int {
return restaurantsList.size
}
override fun onBindViewHolder(holder: HomeRecyclerViewHolder, position: Int) {
val restaurant = restaurantsList[position]
holder.costForOne.text = restaurant.getCostForOne().toString()
holder.rating.text = restaurant.getRestaurantRating().toString()
holder.textView.text = restaurant.getRestaurantName()
Picasso.get().load(restaurant.getRestaurant()).placeholder(R.drawable.food_runner_icon).into(holder.imageView).toString()
holder.btnFavourite.setOnClickListener {
Toast.makeText(context ,"Favourite Button Clicked",Toast.LENGTH_LONG).show()
}
}
class HomeRecyclerViewHolder(view: View) : RecyclerView.ViewHolder(view) {
var imageView: ImageView = view.findViewById(R.id.imgRestaurantImage)
var costForOne: TextView = view.findViewById(R.id.txtCostForOne)
var textView: TextView = view.findViewById(R.id.txtRestaurantName)
var btnFavourite: ImageButton = view.findViewById(R.id.btnFavourite)
var rating: TextView = view.findViewById(R.id.txtRating)
}
}
Firebase数据库结构：[1] ：https://i.stack.imgur.com/XDrxa.png
尽管代码的格式和实现都很好，但应用程序中似乎存在一个错误，不允许应用程序检索和显示数据。
代码中的主要问题在于Restaurants类，其中所有getter的名称都不正确。如果您的类中有一个名为id的属性，那么相应的getter应该是getId()，而不是getRestaurantId()。另一方面，setter应该是setId()，而不是setRestaurantId()。有两种方法可以解决这个问题。第一个是根据上面的例子更改所有getter/setter的所有名称。
另外请注意，setter和getter不是强制性的。setter总是可选的，因为如果JSON属性没有setter，Firebase客户端将直接在字段上设置值。然而，创建这样一个类的一种更简单的方法是直接在构造函数中定义和初始化属性，并将该类设置为data class:
data class Restaurant(
var id: String? = null,
var name: String? = null,
var rating: String? = null,
var cost_for_one: String? = null,
var imageUrl: String? = null
)
还请注意，该类的名称是Restaurant，而不是Restaurants，这是因为该类可以被视为单个餐厅的蓝图，而不是更多餐厅的蓝图。