setAdapter 上的空对象引用错误

Posted 2023-04-18

【中文标题】setAdapter 上的空对象引用错误

【英文标题】：null obejct reference error on setAdapter

【发布时间】：2022-01-15 16:28:50

【问题描述】：

我尝试为我的回收站视图设置一个适配器，但它引发了以下错误 尝试在空对象引用上调用虚拟方法 'void androidx.recyclerview.widget.RecyclerView.setAdapter(androidx.recyclerview.widget.RecyclerView$Adapter)'

这是当前活动的代码

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;
import android.widget.TextView;

public class resourcetab extends AppCompatActivity 
private TextView txt;
 private DataModel2 data =new DataModel2();

    private RecyclerView recyclerView;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_resourcetab);

 data =getIntent().getParcelableExtra("object");
       resourceadapter adapter = new resourceadapter(data);

       recyclerView.setAdapter(adapter);

    

回收器视图适配器的代码

package com.example.myapplication;

import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;

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

import java.util.ArrayList;
import java.util.List;

public class resourceadapter extends RecyclerView.Adapter<resourceadapter.ViewHolder> 
    private List<String> URL= new ArrayList<>();

    private List<String> type=new ArrayList<>();
    private List<String> Giver=new ArrayList<>();
    public resourceadapter(DataModel2 data)
        this.URL=data.URL;
        this.type=data.type;
        this.Giver=data.Giver;
    


    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) 
        View view  = LayoutInflater.from(parent.getContext()).inflate(R.layout.each_resource , parent , false);
        return new ViewHolder(view);
    



    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) 
    URL.get(position);
    holder.type1.setText(type.get(position));
    holder.name1.setText(Giver.get(position));
    holder.liner.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 

        
    );
    

    @Override
    public int getItemCount() 
        return Giver.size();
    

    public class ViewHolder extends RecyclerView.ViewHolder
        private LinearLayout liner ;
        private TextView type1;
        private TextView name1;



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

            liner = itemView.findViewById(R.id.liner);
            name1 = itemView.findViewById(R.id.textView6);
            type1 = itemView.findViewById(R.id.textView7);


        
    

【问题讨论】：

您是否已将 View 分配给您的 recyclerview？

私有 RecyclerView recyclerView = findViewById(R.id.your_recyclerview_id);

【参考方案1】：

在 onCreate 中设置适配器之前，您必须通过 findViewById 方法初始化您的回收站视图。 喜欢，

recyclerView = findViewById(R.id.recView) //id of Recycler View which you given in your xml