i am trying to add name and number in my recyler view contact list but when i click add button the a-CodePudding

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

CodePudding user response：

So at the very beginning of your code, you have declared a variable:

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

    ...
}

But close to the end of your code, you have defined another adapter:

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

The above will only create a new local variable and keeps your top adapter being null.

So if you would like to access adapter in any function within the same class, you should assign to your top declared adapter. And therefore you should remove RecyclerContactAdapter for the bottom one:

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

CodePudding user response：

adapter don't assign obj,you need Assigns a value to a declared variable.

  adapter = new RecyclerContactAdapter(this, arrContact);

CodePudding user response：

You can also add a check, if it's null or not

if(adapter !=null) {
    adapter.notifyItemInserted(arrContact.size()-1);
}