Android Studio 我试图添加姓名和号码在我的recyler查看联系人列表，但当我点击添加按钮的应用程序停止工作并关闭

MainActivity of my code

package com.example.recycleview;

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

import android.app.Dialog;
import android.os.Bundle;
import android.view.View;
import android.widget.Adapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.material.floatingactionbutton.FloatingActionButton;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
ArrayList<ContactModel>arrContact= new ArrayList<>();
RecyclerContactAdapter adapter;
RecyclerView recyclerView;
FloatingActionButton btnOpndlg;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         recyclerView= findViewById(R.id.recycleContact);
        btnOpndlg = findViewById(R.id.btnopndlg);
        btnOpndlg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Dialog dialog = new Dialog(MainActivity.this);
                dialog.setContentView(R.layout.add_update);

                EditText edtname= dialog.findViewById(R.id.edtname);
                EditText edtno= dialog.findViewById(R.id.edtno);
                Button btnActn= dialog.findViewById(R.id.addbtn);
                btnActn.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        String name=" ", number="";

                        if(!edtname.getText().toString().equals("")){
                             name= edtname.getText().toString();

                        }
                        else{
                            Toast.makeText(MainActivity.this, "Please Enter the name ", Toast.LENGTH_SHORT).show();
                        }
                        if(!edtno.getText().toString().equals("")){
                             number= edtno.getText().toString();

                        }
                        else{
                            Toast.makeText(MainActivity.this, "Please Enter the number ", Toast.LENGTH_SHORT).show();
                        }
                        arrContact.add(new ContactModel(name,number));
                         adapter.notifyItemInserted(arrContact.size()-1);
                        recyclerView.scrollToPosition(arrContact.size()-1);
                        dialog.dismiss();
                    }

                });
                dialog.show();

            }
        });


        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        arrContact.add(new ContactModel(R.drawable.ap,"Shank","908784836"));
        arrContact.add(new ContactModel(R.drawable.lp,"Luffy","908784836"));
        arrContact.add(new ContactModel(R.drawable.kl,"Aurther","908784836"));
        arrContact.add(new ContactModel(R.drawable.ss,"madara","908784836"));
        arrContact.add(new ContactModel(R.drawable.gp,"mob","908784836"));
        arrContact.add(new ContactModel(R.drawable.hp,"Sakuna","908784836"));
        arrContact.add(new ContactModel(R.drawable.gp,"mob","908784836"));
        arrContact.add(new ContactModel(R.drawable.ap,"Shank","908784836"));
        arrContact.add(new ContactModel(R.drawable.lp,"luffy","908784836"));
        arrContact.add(new ContactModel(R.drawable.ss,"madra","908784836"));
        arrContact.add(new ContactModel(R.drawable.ss,"madra","908784836"));
        arrContact.add(new ContactModel(R.drawable.ap,"shank","908784836"));
        arrContact.add(new ContactModel(R.drawable.gp,"mob","908784836"));

RecyclerContactAdapter adapter= new RecyclerContactAdapter(this, arrContact);
recyclerView.setAdapter(adapter);

    }
}

FATAL EXCEPTION: main Process: com.example.recycleview, PID: 2731 java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.recycleview.RecyclerContactAdapter.notifyItemInserted(int)' on a null object reference at com.example.recycleview.MainActivity$1$1.onClick(MainActivity.java:59) at android.view.View.performClick(View.java:7448) at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1219) at android.view.View.performClickInternal(View.java:7425) at android.view.View.access$3600(View.java:810) at android.view.View$PerformClick.run(View.java:28305) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:223) at android.app.ActivityThread.main(ActivityThread.java:7656) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
please check the above code mainacitvity

因此，在代码的开头，您已经声明了一个变量：

public class MainActivity extends AppCompatActivity {
    ArrayList<ContactModel>arrContact= new ArrayList<>();
    RecyclerContactAdapter adapter; // You have declared an adapter here
    RecyclerView recyclerView;
    FloatingActionButton btnOpndlg;

    ...
}

但是在代码的末尾，您定义了另一个adapter：

RecyclerContactAdapter adapter= new RecyclerContactAdapter(this, arrContact);
recyclerView.setAdapter(adapter);

上面的代码只会创建一个新的局部变量，并保持adapter为null。
所以如果你想在同一个类中的任何函数中访问adapter，你应该给最上面声明的adapter赋值，因此你应该删除最下面声明的RecyclerContactAdapter：

adapter = new RecyclerContactAdapter(this, arrContact);
recyclerView.setAdapter(adapter);

Android Studio 我试图添加姓名和号码在我的recyler查看联系人列表，但当我点击添加按钮的应用程序停止工作并关闭

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