尝试在 recyclerview kotlin 上的空对象引用上调用虚拟方法 'void android.widget.TextView.setText(java.lang.CharSequence)
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【中文标题】尝试在 recyclerview kotlin 上的空对象引用上调用虚拟方法 \'void android.widget.TextView.setText(java.lang.CharSequence)\'【英文标题】：Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference on recyclerview kotlin尝试在 recyclerview kotlin 上的空对象引用上调用虚拟方法 'void android.widget.TextView.setText(java.lang.CharSequence)' 【发布时间】：2020-09-28 16:51:55 【问题描述】：尝试在空对象引用上调用虚拟方法“void android.widget.TextView.setText(java.lang.CharSequence)”
所以我只学了 3 周的 kotlin 就卡住了
这是我的 MainActivity.kt
package com.go.personalitieslist
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.provider.ContactsContract
import android.view.Menu
import android.view.MenuItem
import android.view.View
import android.widget.Toast
import androidx.appcompat.widget.Toolbar
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
class MainActivity : AppCompatActivity()
private lateinit var rvPersonalities: RecyclerView
private var list: ArrayList<Personalities> = arrayListOf()
private lateinit var listPersonalitiesAdapter: ListPersonalitiesAdapter
override fun onCreate(savedInstanceState: Bundle?)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val mtoolbar = findViewById<View>(R.id.toolbar) as Toolbar
setSupportActionBar(mtoolbar)
rvPersonalities = findViewById(R.id.rv_personalities)
rvPersonalities.setHasFixedSize(true)
list.addAll(PersonalitiesData.listData)
showRecyclerList()
override fun onCreateOptionsMenu(menu: Menu?): Boolean
menuInflater.inflate(R.menu.main_menu,menu)
return super.onCreateOptionsMenu(menu)
override fun onOptionsItemSelected(item: MenuItem): Boolean
val id = item.itemId
val intent = Intent(this, About::class.java)
when(id)
R.id.profile-> startActivity(intent)
return super.onOptionsItemSelected(item)
private fun showRecyclerList()
rvPersonalities.layoutManager = LinearLayoutManager(this)
val listPersonalitiesAdapter = ListPersonalitiesAdapter(list)
rvPersonalities.adapter = listPersonalitiesAdapter
listPersonalitiesAdapter.setOnItemClickCallback(object : ListPersonalitiesAdapter.OnItemClickCallback
override fun onItemClicked(data: Personalities)
val detailIntent = Intent(this@MainActivity, DetailPage::class.java).apply
putExtra(DetailPage.EXTRA_NAME,data.name)
putExtra(DetailPage.EXTRA_DETAIL,data.detail)
putExtra(DetailPage.EXTRA_PHOTO,data.photo)
showSelectedPersonalities(data)
startActivity(detailIntent)
)
private fun showSelectedPersonalities(personalities: Personalities)
Toast.makeText(this, personalities.name, Toast.LENGTH_SHORT).show()
这是 ListPersonalitiesAdapter.kt
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import kotlinx.android.synthetic.main.item_row_personalities.view.*
class ListPersonalitiesAdapter(val listPersonalities:ArrayList<Personalities>) : RecyclerView.Adapter<ListPersonalitiesAdapter.ListViewHolder>()
private lateinit var onItemClickCallback: OnItemClickCallback
fun setOnItemClickCallback(onItemClickCallback: OnItemClickCallback)
this.onItemClickCallback = onItemClickCallback
override fun onCreateViewHolder(viewGroup: ViewGroup, i: Int): ListViewHolder
val view: View = LayoutInflater.from(viewGroup.context).inflate(R.layout.item_row_personalities, viewGroup, false)
return ListViewHolder(view)
override fun onBindViewHolder(holder: ListViewHolder, position: Int)
holder.bind(listPersonalities[position])
holder.itemView.setOnClickListener()
onItemClickCallback.onItemClicked(listPersonalities[holder.adapterPosition])
/*
val personalities = listPersonalities[position]
Glide.with(holder.itemView.context)
.load(personalities.photo)
.apply(RequestOptions().override(55, 55))
.into(holder.imgPhoto)
holder.tvName.text = personalities.name
holder.tvDetail.text = personalities.detail
holder.itemView.setOnClickListener
onItemClickCallback.onItemClicked(listPersonalities[holder.adapterPosition])
*/
override fun getItemCount(): Int
return listPersonalities.size
class ListViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)
fun bind(item : Personalities)
with(itemView)
tv_item_name.text = item.name
tv_item_detail.text = item.detail
Glide.with(this).load(item.photo).into(img_item_photo)
//var tvName: TextView = itemView.findViewById(R.id.tv_item_name)
// var tvDetail: TextView = itemView.findViewById(R.id.tv_item_detail)
// var imgPhoto: ImageView = itemView.findViewById(R.id.img_item_photo)
interface OnItemClickCallback
fun onItemClicked(data: Personalities)
这是 DetailPage.kt
class DetailPage : AppCompatActivity()
companion object
val EXTRA_NAME = "extra_name"
val EXTRA_DETAIL = "extra_detail"
val EXTRA_PHOTO = "extra_photo"
override fun onCreate(savedInstanceState: Bundle?)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_detail)
showDetailPersonalities()
private fun showDetailPersonalities()
tv_item_name.setText(intent.getStringExtra(EXTRA_NAME))
tv_item_detail.setText(intent.getStringExtra(EXTRA_DETAIL))
Glide.with(this).load(intent.getIntExtra(EXTRA_PHOTO,0)).into(img_item_photo)
这是显示详细信息页面的activity_detail.xml
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_
android:layout_>
<ScrollView
android:layout_
android:layout_
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:layout_
android:layout_
android:orientation="vertical" >
<de.hdodenhof.circleimageview.CircleImageView
android:id="@+id/extra_photo"
android:layout_
android:layout_
android:contentDescription="@string/todo"
tools:background="@drawable/ic_launcher_background" />
<TextView
android:id="@+id/extra_name"
android:layout_
android:layout_
android:layout_marginTop="20dp"
android:layout_marginBottom="15dp"
android:fontFamily="sans-serif"
android:textAlignment="center"
android:textAppearance="@style/TextAppearance.AppCompat.Display1"
android:textSize="30sp"
android:textStyle="bold"
android:typeface="normal" />
<TextView
android:id="@+id/extra_detail"
android:layout_
android:layout_
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginBottom="10dp"
android:fontFamily="sans-serif"
android:textAlignment="viewStart"
android:textSize="18sp" />
</LinearLayout>
</ScrollView>
</androidx.constraintlayout.widget.ConstraintLayout>
这是调试器按摩
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.go.personalitieslist, PID: 14854
java.lang.RuntimeException: Unable to start activity ComponentInfocom.go.personalitieslist/com.go.personalitieslist.DetailPage: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.go.personalitieslist.DetailPage.showDetailPersonalities(DetailPage.kt:29)
at com.go.personalitieslist.DetailPage.onCreate(DetailPage.kt:23)
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
【问题讨论】：
我认为您活动中的这一行缺少 import kotlinx.android.synthetic.main.activity_log_in.* activity_log_in = name of xml => 【参考方案1】：您在 DetailPage 活动中的 ID 为 tv_item_name 和 tv_item_name 的 TextView 上设置文本，但您的 activity_detail.xml 中没有带有这些 ID 的 TextView。
您想要做的是调用extra_name 和extra_detail：
private fun showDetailPersonalities()
extra_name.setText(intent.getStringExtra(EXTRA_NAME)) //change this
extra_detail.setText(intent.getStringExtra(EXTRA_DETAIL)) //and this
Glide.with(this).load(intent.getIntExtra(EXTRA_PHOTO,0)).into(img_item_photo)
【讨论】：
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