title: com.google.firebase.auth.FirebaseAuth.getCurrentUser()' on a null object reference
body: <pre><code>package com.example.firebase_project;
  
  import android.app.ProgressDialog;
  import android.content.Intent;
  import android.support.annotation.NonNull;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.text.TextUtils;
   import android.view.View;
   import android.widget.Button;
  import android.widget.EditText;
  import android.widget.TextView;
  import android.widget.Toast;
  
  import com.google.android.gms.tasks.OnCompleteListener;
  import com.google.android.gms.tasks.Task;
  import com.google.firebase.auth.AuthResult;
  import com.google.firebase.auth.FirebaseAuth;
  import com.google.firebase.auth.FirebaseUser;
  
  public class LoginActivity extends AppCompatActivity {
  private   FirebaseUser currentuser;
  private   Button loginbutton,PhoneLoginButton;
  private  TextView forgetPasswordLink,NeedNewAccountLink;
  private  EditText UserEmail,UserPassword;
   private FirebaseAuth mAuth;
   private ProgressDialog loadingBar;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_login);
      InatlizeField();
  
      currentuser=mAuth.getCurrentUser();
      mAuth=FirebaseAuth.getInstance();
      NeedNewAccountLink.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              SendUserToRegisterActivity();
          }
      });
      loginbutton.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              AllowUserToLogin();
          }
      });
  }
  
  private void AllowUserToLogin() {
      String Email=UserEmail.getText().toString();
      String Password=UserPassword.getText().toString();
      if(TextUtils.isEmpty(Email))
      {
          Toast.makeText(this,"plz enter email",Toast.LENGTH_SHORT).show();
      }
      if(TextUtils.isEmpty(Password))
      {
          Toast.makeText(this,"plz enter password",Toast.LENGTH_SHORT).show();
      }
      else{
          loadingBar.setTitle("Log in");
          loadingBar.setMessage("plz wait");
          loadingBar.setCanceledOnTouchOutside(true);
          mAuth.signInWithEmailAndPassword(Email,Password).addOnCompleteListener(new OnCompleteListener&lt;AuthResult&gt;() {
              @Override
              public void onComplete(@NonNull Task&lt;AuthResult&gt; task) {
                  if(task.isSuccessful())
                  {
                      sendtoMainActivity();
                      Toast.makeText(LoginActivity.this,"Login success ful",Toast.LENGTH_SHORT).show();
                      loadingBar.dismiss();
                  }
                  else {
                      String massage = task.getException().toString();
                      Toast.makeText(LoginActivity.this, massage, Toast.LENGTH_SHORT).show();
                      loadingBar.dismiss();
  
                  }
  
                  }
          });
  
      }
  }
  
  private void sendtoMainActivity() {
      Intent MainIntent=new Intent(LoginActivity.this,MainActivity.class);
      startActivity(MainIntent);
  
  }
  
  protected  void InatlizeField()
  {
     loginbutton=(Button)findViewById(R.id.login_button);
     PhoneLoginButton=(Button)findViewById(R.id.phone_login);
     forgetPasswordLink=(TextView)findViewById(R.id.forget_password);
     NeedNewAccountLink=(TextView)findViewById(R.id.create_account);
     UserEmail=(EditText)findViewById(R.id.login_email);
     UserPassword=(EditText)findViewById(R.id.login_password);
      loadingBar=new ProgressDialog(this);
  }
  
  @Override
  protected void onStart() {
      super.onStart();
      if(currentuser !=null)
      {
          SendUserToMainActivity();
      }
  }
  protected void SendUserToMainActivity()
  {
      Intent MainActivityIntent=new Intent(LoginActivity.this,MainActivity.class);
      startActivity(MainActivityIntent);
  }
  protected void SendUserToRegisterActivity()
  {
      Intent RegisterIntent=new Intent(LoginActivity.this,RegisterActivity.class);
      startActivity(RegisterIntent);
  }
  </code></pre>
  
  <p>}</p>
  
  <p>MainActivity.java</p>
  
  <pre><code>package com.example.firebase_project;
  
  import android.app.ProgressDialog;
  import android.content.Intent;
  import android.support.design.widget.TabLayout;
  import android.support.v4.view.ViewPager;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.support.v7.widget.Toolbar;
  import android.view.Menu;
  import android.view.MenuItem;
  
  import com.google.firebase.auth.FirebaseAuth;
  import com.google.firebase.auth.FirebaseUser;
  
  public class MainActivity extends AppCompatActivity {
  Toolbar toolbar;
  private ViewPager viewPager;
  private TabLayout tabLayout;
  private TabAcessAdaptor tabAcessAdaptor;
  private FirebaseUser currentuser;
  private FirebaseAuth mAuth;
  
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      mAuth = FirebaseAuth.getInstance();
      currentuser=mAuth.getCurrentUser();
  
  
      toolbar=(Toolbar)findViewById(R.id.main_page_toolbar);
      setSupportActionBar(toolbar);
      getSupportActionBar().setTitle("Created By Sumit Kumar");
  
  
      viewPager=(ViewPager)findViewById(R.id.main_tab_paper);
      tabAcessAdaptor=new TabAcessAdaptor(getSupportFragmentManager());
      viewPager.setAdapter(tabAcessAdaptor);
  
      tabLayout=(TabLayout)findViewById(R.id.main_tabs);
      tabLayout.setupWithViewPager(viewPager);
  
  }
  
  @Override
  protected void onStart() {
      super.onStart();
      if(currentuser ==null)
      {
          SendUserToLoginPge();
      }
  }
  private void SendUserToLoginPge()
  {
      Intent LoginIntent=new Intent(MainActivity.this,LoginActivity.class);
      startActivity(LoginIntent);
  }
  
  @Override
  public boolean onCreateOptionsMenu(Menu menu)
  {
      super.onCreateOptionsMenu(menu);
  
      getMenuInflater().inflate(R.menu.option_menu, menu);
      return true;
  }
  
  @Override
  public boolean onOptionsItemSelected(MenuItem item)
  {
      super.onOptionsItemSelected(item);
      if (item.getItemId()==R.id.main_find_friend_option)
      {
  
      }
      if (item.getItemId()==R.id.main_setting_option)
      {
  
      }
      if (item.getItemId()==R.id.main_logout_option)
      {
          mAuth.signOut();
          sendUserToLoginPge();
      }
      return  true;
  }
  
  private void sendUserToLoginPge() {
      Intent intent =new Intent(MainActivity.this,LoginActivity.class);
      startActivity(intent);
  }
  </code></pre>
  
  <p>}</p>
  
  <p>when i creating login and signup a with firebase authantification</p>
  
  <p>getting error ** Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.auth.FirebaseUser com.google.firebase.auth.FirebaseAuth.getCurrentUser()' on a null object reference at com.example.firebase_project.LoginActivity.onCreate(LoginActivity.java:35)**</p>
  
  <p>private FirebaseUser currentuser;
  currentuser=mAuth.getCurrentUser();</p>
  
  <p>i dont know how It show nullPointerexception</p>