为啥 recyclerview$adapter 在片段中为空

Posted 2023-04-18

【中文标题】为啥 recyclerview$adapter 在片段中为空

【英文标题】：why recyclerview$adapter is null in fragment为什么 recyclerview$adapter 在片段中为空

【发布时间】：2021-11-19 15:05:12

【问题描述】：

这是我的错误代码......

我正在尝试创建一个片段来读取联系人，但是当我运行它时它崩溃了......

但这不会发生在活动中......

java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setAdapter(androidx.recyclerview.widget.RecyclerView$Adapter)' on a null object reference
    at com.*******"".****.manuTwo.ContactsFragment.GetData(ContactsFragment.java:82)
    at com.**********.******manuTwo.ContactsFragment.onCreate(ContactsFragment.java:42)
    at androidx.fragment.app.Fragment.performCreate(Fragment.java:2949)
    at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
    at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
    at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
    at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
    at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1971)
    at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:311)
    at androidx.fragment.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:249)
    at androidx.viewpager.widget.ViewPager.populate(ViewPager.java:1244)
    at androidx.viewpager.widget.ViewPager.setCurrentItemInternal(ViewPager.java:669)
    at androidx.viewpager.widget.ViewPager.setCurrentItemInternal(ViewPager.java:631)
    at androidx.viewpager.widget.ViewPager.setCurrentItem(ViewPager.java:612)
    at com.google.android.material.tabs.TabLayout$ViewPagerOnTabSelectedListener.onTabSelected(TabLayout.java:3401)
    at com.google.android.material.tabs.TabLayout.dispatchTabSelected(TabLayout.java:1856)
    at com.google.android.material.tabs.TabLayout.selectTab(TabLayout.java:1849)
    at com.google.android.material.tabs.TabLayout.selectTab(TabLayout.java:1809)
    at com.google.android.material.tabs.TabLayout$Tab.select(TabLayout.java:2249)
    at com.google.android.material.tabs.TabLayout$TabView.performClick(TabLayout.java:2438)
    at android.view.View.performClickInternal(View.java:7284)
    at android.view.View.access$3600(View.java:821)
    at android.view.View$PerformClick.run(View.java:28053)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:226)
    at android.app.ActivityThread.main(ActivityThread.java:7592)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

【问题讨论】：

请包含您的一些被此异常引用的代码，以便我们验证问题出在哪里。

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【参考方案1】：

这是我的适配器：

package com.myphone.contact.adapter.UserContactsAdapter;

import android.view.View;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.google.android.material.imageview.ShapeableImageView;
import com.myphone.contact.R;

public class UserContactAdapter extends RecyclerView.ViewHolder 

    public ShapeableImageView ImageProfile;
    public TextView usersName, userPhone, userStatus, hiFriend;

    public UserContactAdapter(@NonNull View itemView) 
        super(itemView);

        ImageProfile = (ShapeableImageView) itemView.findViewById(R.id.user_image_contact_friend);
        usersName = (TextView) itemView.findViewById(R.id.user_Name_contact_friend);
        userPhone = (TextView) itemView.findViewById(R.id.user_Phone_contact_friend);
        userStatus = (TextView) itemView.findViewById(R.id.status_user_contact_friend);
        hiFriend = (TextView) itemView.findViewById(R.id.hi_my_friend);