RecyclerView中输入EditText时应用崩溃，求问题原因及解决办法

我想在RecyclerView的每一行中，对相邻EditText的数值进行累加计算，并将累加结果显示在该行的TextView中。应用启动时一切正常，但在任意EditText中输入内容时，应用会崩溃关闭。请问为何输入EditText时应用会崩溃？

MainActivity代码： #

package com.example.recyclerview;

import android.os.Bundle;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    ArrayList<Model> models = new ArrayList<>();
    Adapter adapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;

        });
        setDataItems();

        RecyclerView recyclerView = findViewById(R.id.rv);
        Adapter adapter = new Adapter(models,this);
        recyclerView.setAdapter(adapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setItemViewCacheSize(100);


    }public void recalculateTotals(){
          double currentTotal = 0;
          for(int i=0;i<models.size();i++){
              currentTotal += Double.parseDouble(models.get(i).getValue());
              models.get(i).setRunningTotal(String.valueOf(currentTotal));
          }adapter.notifyDataSetChanged();
    }
    private void setDataItems(){

        String[] edittexts = getResources().getStringArray(R.array.edittexts);
        String[] textviews = getResources().getStringArray(R.array.textviews);
        for(int i =0; i < edittexts.length; i++){
            models.add(new Model(edittexts[i],textviews[i]));
        }
    }
}

Adapter类代码： #

package com.example.recyclerview;

import android.content.Context;
import android.text.Editable;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.TextSwitcher;
import android.widget.TextView;
import android.widget.Toast;

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

import org.w3c.dom.Text;

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

public class Adapter extends RecyclerView.Adapter<Adapter.MyViewHolger> {
    ArrayList<Model> models = new ArrayList<>();

    Context context;
    MainActivity activity;

    public Adapter(MainActivity activity) {
        this.activity = activity;
    }

    public Adapter(ArrayList<Model> models, Context context) {
        this.models = models;
        this.context = context;
    }

    @NonNull
    @Override
    public Adapter.MyViewHolger onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

        View view = LayoutInflater.from(context).inflate(R.layout.row, parent, false);
        return new MyViewHolger(view);
    }

    @Override
    public void onBindViewHolder(@NonNull Adapter.MyViewHolger holder, int position) {
      Model currentItem = models.get(position);


       if(holder.et.getTag()instanceof TextWatcher){
           holder.et.removeTextChangedListener((TextWatcher) holder.et.getTag());
       }
       holder.et.setText(currentItem.getValue());
       holder.tv.setText(currentItem.getRunningTotal());

       MyTextWatcher watcher = new MyTextWatcher(holder.et,position);
       holder.et.addTextChangedListener(watcher);
       holder.et.setTag(watcher);
    }

    @Override
    public int getItemCount() {
        return models.size();
    }


    public static class MyViewHolger extends RecyclerView.ViewHolder {
        TextView tv;
        EditText et;


        public MyViewHolger(@NonNull View itemView) {
            super(itemView);
            tv = itemView.findViewById(R.id.tv);
            et = itemView.findViewById(R.id.et);

        }
    }
    private class MyTextWatcher implements TextWatcher{
        EditText et;
        int position;

        public MyTextWatcher(EditText et, int position) {
            this.et = et;
            this.position = position;
        }

        @Override
        public void afterTextChanged(Editable s) {

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            try{
                double value = Double.parseDouble((s.toString()));
                models.get(position).setValue(String.valueOf(value));

            }catch (NumberFormatException e){
                models.get(position).setValue(String.valueOf(0));

            }activity.recalculateTotals();

        }
    }
}

崩溃原因分析及修复方案 #

核心崩溃原因：空指针异常（NullPointerException） #

• Adapter中的activity变量未初始化
  你在MainActivity中创建Adapter时调用的是new Adapter(models,this)，但该构造函数仅给models和context赋值，未初始化activity变量。当EditText输入内容触发onTextChanged时，调用activity.recalculateTotals()会因activity为null抛出空指针异常，直接导致应用崩溃。

• MainActivity中的成员变量adapter未正确赋值
  在MainActivity的onCreate方法中，你重新定义了局部变量Adapter adapter = new Adapter(models,this)，覆盖了成员变量adapter，导致成员变量始终为null。当recalculateTotals()调用adapter.notifyDataSetChanged()时，同样会触发空指针异常。

具体修复步骤： #

1. 修改Adapter构造函数，初始化activity

合并或修改Adapter的构造函数，确保创建时能同时传入models、context和activity：

public Adapter(ArrayList<Model> models, Context context, MainActivity activity) {
    this.models = models;
    this.context = context;
    this.activity = activity;
}

2. 修复MainActivity中adapter的赋值问题

在onCreate中直接给成员变量adapter赋值，避免定义局部变量覆盖：

// 去掉局部变量定义，直接赋值给成员变量
adapter = new Adapter(models,this,this);
recyclerView.setAdapter(adapter);

3. 优化EditText输入处理（可选）

提前判断空输入，避免不必要的异常捕获：

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
    String input = s.toString().trim();
    if(TextUtils.isEmpty(input)){
        models.get(position).setValue("0");
    }else{
        try{
            double value = Double.parseDouble(input);
            models.get(position).setValue(String.valueOf(value));
        }catch (NumberFormatException e){
            models.get(position).setValue("0");
        }
    }
    activity.recalculateTotals();
}

经过以上修复，输入EditText时应用不会再崩溃，累加计算功能也能正常运行。

内容的提问来源于stack exchange，提问作者kaismaqbool hakim