setAdapter 上的空对象引用错误

Question

我已经尝试为我的回收站视图设置一个适配器，但它抛出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);


        }
    }
}

Answer 1

在 onCreate 中设置适配器之前，您必须通过 findViewById 方法初始化您的 recyclerview。喜欢，

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

setAdapter 上的空对象引用错误

null obejct reference error on setAdapter

java

android

android-recyclerview

android-adapter