App crashes when I open another activity register

Question

this is my register activity class code anyone help me to fix and find error on this code and tell me please

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.app.ProgressDialog;
import android.content.Intent;
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.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
public class RegisterActivity extends AppCompatActivity {

  private Button CreateAccountButton;
  private EditText UserEmail, UserPassowrd;
  private TextView AlreadyHaveAccountLink;
  private FirebaseAuth mAuth;
  private DatabaseReference RootRef;
  private static long back_pressed;
  private static int Time_Delay = 2000;
  private ProgressDialog loadingBar;



  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_register);

    mAuth = FirebaseAuth.getInstance();
    RootRef = FirebaseDatabase.getInstance().getReference();

    InitializeFileds();


    AlreadyHaveAccountLink.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        SendUserToLoginActivity();
      }
    });


    CreateAccountButton.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        CreateNewAccount();
      }
    });
  }



  private void CreateNewAccount() {
    String email = UserEmail.getText().toString();
    String password = UserPassowrd.getText().toString();

    if (TextUtils.isEmpty(email)) {
      Toast.makeText(this, "Please Enter Email...", Toast.LENGTH_SHORT).show();
    }
    if (TextUtils.isEmpty(password)) {
      Toast.makeText(this, "Please Enter Password...", Toast.LENGTH_SHORT).show();
    } else {

      loadingBar.setTitle("Creating New Account");
      loadingBar.setMessage("PLease Wait, while we were creating new account for you...");
      loadingBar.setCanceledOnTouchOutside(true);
      loadingBar.show();

      mAuth.createUserWithEmailAndPassword(email, password)
        .addOnCompleteListener(new OnCompleteListener < AuthResult > () {
          @Override
          public void onComplete(@NonNull Task < AuthResult > task) {
            if (task.isSuccessful()) {
              String currentUserID = mAuth.getCurrentUser().getUid();
              RootRef.child("Users").child(currentUserID).setValue("");

              SendUserToMainActivity();
              Toast.makeText(RegisterActivity.this, "Account Created Successfully...", Toast.LENGTH_SHORT).show();
              loadingBar.dismiss();
            } else {
              String message = task.getException().toString();
              Toast.makeText(RegisterActivity.this, "Error : " + message, Toast.LENGTH_SHORT).show();
              loadingBar.dismiss();
            }
          }
        });
    }
  }



  private void InitializeFileds() {
    CreateAccountButton = (Button) findViewById(R.id.register_button);
    UserEmail = (EditText) findViewById(R.id.register_email);
    UserPassowrd = (EditText) findViewById(R.id.register_password);
    AlreadyHaveAccountLink = (TextView) findViewById(R.id.already_account_have_link);

    loadingBar = new ProgressDialog(this);
  }



  private void SendUserToLoginActivity() {
    Intent loginIntent = new Intent(RegisterActivity.this, LoginActivity.class);
    startActivity(loginIntent);
  }
  private void SendUserToMainActivity() {
    Intent mainIntent = new Intent(RegisterActivity.this, MainActivity.class);
    mainIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
    startActivity(mainIntent);
    finish();
  }

  @Override
  public void onBackPressed() {
    if (back_pressed + Time_Delay > System.currentTimeMillis()) {
      Intent intent = new Intent(Intent.ACTION_MAIN);
      intent.addCategory(Intent.CATEGORY_HOME);
      intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
      startActivity(intent);
      finish();
    } else {
      Toast.makeText(this, "Press again to exit", Toast.LENGTH_SHORT).show();
    }
    back_pressed = System.currentTimeMillis();
  }
}