我正在Android Studio中制作一个Kotlin应用程序,我可以像列表一样添加食物及其卡路里值。
它的工作原理是,两个EditText组件,“etName”和“etCalories”,将被传递到一个列表中,然后RecyclerView中的TextView应该显示它们。
问题是,如果我按下按钮添加项目,应用程序会崩溃。
这是logcat
FATAL EXCEPTION: main
Process: com.example.bbar, PID: 25930
java.lang.NullPointerException
at com.example.bbar.ui.home.FoodlistadapterKt.getBinding(foodlistadapter.kt:16)
at com.example.bbar.ui.home.FoodlistadapterKt.access$getBinding(foodlistadapter.kt:1)
at com.example.bbar.ui.home.Foodlistadapter.onBindViewHolder(foodlistadapter.kt:57)
at com.example.bbar.ui.home.Foodlistadapter.onBindViewHolder(foodlistadapter.kt:18)
这是密码
foodlistadapter.kt
package com.example.bbar.ui.home
import android.annotation.SuppressLint
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.example.bbar.R
import android.graphics.Paint.STRIKE_THRU_TEXT_FLAG
import android.widget.TextView
import com.example.bbar.databinding.FooditemBinding
@SuppressLint("StaticFieldLeak")
private var _binding: FooditemBinding? = null
private val binding get() = _binding!!
class Foodlistadapter(
private val foods: MutableList<food>
) : RecyclerView.Adapter<Foodlistadapter.foodlistviewholder>() {
class foodlistviewholder(itemView: View) : RecyclerView.ViewHolder(itemView)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): foodlistviewholder {
return foodlistviewholder(
LayoutInflater.from(parent.context).inflate(
R.layout.fragment_home,
parent,
false
)
)
}
fun addFood(food: food) {
foods.add(food)
notifyItemInserted(foods.size - 1)
}
fun deleteFood() {
foods.removeAll { foods -> foods.isChecked }
notifyDataSetChanged()
}
private fun toggleStrikeThrough(tvFood: TextView, isChecked: Boolean) {
if (isChecked) {
tvFood.paintFlags = tvFood.paintFlags or STRIKE_THRU_TEXT_FLAG
} else {
tvFood.paintFlags = tvFood.paintFlags or STRIKE_THRU_TEXT_FLAG.inv()
}
}
override fun onBindViewHolder(holder: foodlistviewholder, position: Int) {
val currentFood = foods[position]
holder.itemView.apply {
binding.tvFood.text = currentFood.name
binding.tvCalories.text= currentFood.calories.toString()
binding.cbDelete.isChecked = currentFood.isChecked
toggleStrikeThrough(binding.tvFood, currentFood.isChecked)
binding.cbDelete.setOnCheckedChangeListener { _, isChecked ->
toggleStrikeThrough(binding.tvFood, isChecked)
currentFood.isChecked = !currentFood.isChecked
}
}
}
override fun getItemCount(): Int {
return foods.size
}
}
package com.example.bbar.ui.home
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.bbar.R
import com.example.bbar.databinding.FragmentHomeBinding
class HomeFragment : Fragment() {
private var _binding: FragmentHomeBinding? = null
private val binding get() = _binding!!
private lateinit var foodlistadapter: Foodlistadapter
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentHomeBinding.inflate(inflater, container, false)
return binding!!.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
foodlistadapter = Foodlistadapter(mutableListOf())
binding.rvFoodItems.adapter = foodlistadapter
binding.rvFoodItems.layoutManager = LinearLayoutManager(activity)
binding.bSubmit.setOnClickListener{
val foodTitle= binding.etName.text.toString()
val foodCalories = binding.etCalories.text.toString()
if (foodTitle.isNotEmpty()){
val food= food(foodTitle, foodCalories.toInt(), false )
foodlistadapter.addFood(food)
binding.etName.text.clear()
binding.etCalories.text.clear()
}
}
binding.bDelete.setOnClickListener{
foodlistadapter.deleteFood()
}
}
override fun onDestroy() {
super.onDestroy()
_binding = null
}
}
摘要:试图添加食物与其尊重的卡路里值与一个按钮,但程序崩溃。
1条答案
按热度按时间ohtdti5x1#
你的
binding
是空的,而且它没有被正确使用。首先,删除类外部的声明,即:
将
ViewHolder
实现更改为:在
onCreateViewHolder
中膨胀绑定:使用
onBindViewHolder
中的绑定: