Android Studio 사이드바 로그인 버튼

게시물 수정 , 삭제는 로그인 필요

사이드바에서 로그인 버튼 생성하고 메소드 작성했는데 Logcat에서 에러 발생하네요

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

        at com.cookandroid.sample.MainActivity.onCreate(MainActivity.java:55)

MainActivity.java

package com.cookandroid.sample;

import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.Menu;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.FrameLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.material.snackbar.Snackbar;
import com.google.android.material.navigation.NavigationView;

import androidx.appcompat.app.AlertDialog;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;

import com.cookandroid.sample.databinding.ActivityMainBinding;

import java.util.zip.Inflater;

public class MainActivity extends AppCompatActivity {

private AppBarConfiguration mAppBarConfiguration;
  private ActivityMainBinding binding;

  TextView tvName, tvEmail;
  EditText dlgEdtName, dlgEdtEmail;
  TextView toastText;
  Button btnLogin;
  View dialogView, toastView;
  Inflater inflater;
  FrameLayout container;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

     btnLogin = (Button) findViewById(R.id.btnLogin);


//        container = (FrameLayout) findViewById(R.id.container);
//        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.dialog, container, false);




 ------------------55번째 줄--------------------------

btnLogin.setOnClickListener(new View.OnClickListener()
        {
@Override
       public void onClick(View view) {
dialogView = (View) View.inflate(MainActivity.this, R.layout.dialog, null);
          AlertDialog.Builder dlg = new AlertDialog.Builder(MainActivity.this);
          dlg.setTitle("사용자 정보 입력");
          dlg.setView(dialogView);
          dlg.setPositiveButton("OK",
                    new DialogInterface.OnClickListener() {
@Override
                       public void onClick(DialogInterface dialog, int which) {
dlgEdtName = (EditText) dialogView.findViewById(R.id.dlgEdt1);
                           dlgEdtEmail = (EditText) dialogView.findViewById(R.id.dlgEdt2);

                           tvName.setText(dlgEdtName.getText().toString());
                           tvEmail.setText(dlgEdtEmail.getText().toString());
                      }
                        });
          dlg.setNegativeButton("Cancel",
                    new DialogInterface.OnClickListener() {
@Override
                       public void onClick(DialogInterface dialog, int which) {
                                Toast toast = new Toast(MainActivity.this);
                           toastView = (View) View.inflate(MainActivity.this,
                                  R.layout.toast1, null );
                           toastText = (TextView) toastView.findViewById(R.id.toastText1);
                           toastText.setText("Canceled");
                          toast.setView(toastView);
                          toast.show();
                      }
                        });
          dlg.show();
      }
        });

     binding = ActivityMainBinding.inflate(getLayoutInflater());
    setContentView(binding.getRoot());

    setSupportActionBar(binding.appBarMain.toolbar);
     binding.appBarMain.fab.setOnClickListener(new View.OnClickListener() {
@Override
       public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
      }
        });
    DrawerLayout drawer = binding.drawerLayout;
    NavigationView navigationView = binding.navView;
     // Passing each menu ID as a set of Ids because each
  // menu should be considered as top level destinations.
     mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home, R.id.nav_springsummer, R.id.nav_fallwinter)
                .setOpenableLayout(drawer)
                .build();
    NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
    NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
    NavigationUI.setupWithNavController(navigationView, navController);
  }

@Override
   public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
  return true;
  }

@Override
   public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
    return NavigationUI.navigateUp(navController, mAppBarConfiguration)
                || super.onSupportNavigateUp();
  }


}