My app are crashing everytime i click on register

Issue

I'm trying to make an app because of work at school but I can't solve this error (Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener(android.view.View$OnClickListener) )' on a null object reference at com.grupo1.denu1.RegisterActivity.onCreate(RegisterActivity.java:40), it occurs every time I try to open the registration activity, so I hope someone can help me

my code

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

private TextView register;
private EditText editTextEmail, editTextPassword;
private Button signIn;

private FirebaseAuth mAuth;
private ProgressBar progressBar;

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

    register= (TextView) findViewById(R.id.register);
    register.setOnClickListener (this);

    signIn = (Button) findViewById(R.id.singIn);
    signIn.setOnClickListener(this);

    editTextEmail = (EditText) findViewById(R.id.email);
    editTextPassword = (EditText) findViewById(R.id.password);

    progressBar = (ProgressBar) findViewById(R.id.progressBar);

    mAuth = FirebaseAuth.getInstance();
}

@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.register:
            startActivity(new Intent(this, RegisterActivity.class));
            break;

        case R.id.singIn:
            userLogin();
            break;
    }
}

private void userLogin() {
    String email = editTextEmail.getText().toString().trim();
    String password = editTextPassword.getText().toString().trim();

    if (email.isEmpty()){
        editTextEmail.setError("Insira o Email!");
        editTextEmail.requestFocus();
        return;
    }

    if (!Patterns.EMAIL_ADDRESS.matcher(email).matches()){
        editTextEmail.setError("Coloque um email válido!");
        editTextEmail.requestFocus();
        return;
    }

    if (password.isEmpty()){
        editTextPassword.setError("Insira a senha!");
        editTextPassword.requestFocus();
        return;
    }

    if (password.length() < 6){
        editTextPassword.setError("Senha precisa ter no minimo 6 caracteres!");
        editTextPassword.requestFocus();
        return;
    }
    progressBar.setVisibility(View.VISIBLE);

    mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> task) {
            if(task.isSuccessful()){
                startActivity(new Intent(MainActivity.this, MenuBase.class));
            }else{
                Toast.makeText(MainActivity.this, "Falha no Login! Tente novamente",Toast.LENGTH_LONG).show();
            }
        }
    });
}

xml:

    <?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/banner"
        android:layout_width="285dp"
        android:layout_height="45dp"
        android:text="Denu"
        android:textSize="40dp"
        android:gravity="center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.496"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.176" />

    <EditText
        android:id="@+id/email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="Email:"
        android:inputType="textEmailAddress"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.351" />

    <Button
        android:id="@+id/singIn"
        android:layout_width="178dp"
        android:layout_height="52dp"
        android:text="Entrar"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.572" />

    <TextView
        android:id="@+id/forgotPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Esqueceu a Senha?"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.632" />

    <EditText
        android:id="@+id/password"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="Senha:"
        android:inputType="textPassword"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.465" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.793" />

    <TextView
        android:id="@+id/register"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Registrar"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.933" />
</androidx.constraintlayout.widget.ConstraintLayout>

RegisterActivity

package com.grupo1.denu1;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Patterns;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
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.FirebaseDatabase;


import java.util.regex.Pattern;

public class RegisterActivity extends AppCompatActivity implements View.OnClickListener {
    private TextView banner, registerUser;
    private EditText editTextFullName, editTextAge, editTextEmail, editTextPassword;
    private ProgressBar progressBar;

    private FirebaseAuth mAuth;

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

        mAuth = FirebaseAuth.getInstance();

        banner = (TextView)findViewById(R.id.banner);
        banner.setOnClickListener(this);

        registerUser = (Button) findViewById(R.id.registerUser);
        registerUser.setOnClickListener(this);

        editTextFullName = (EditText) findViewById(R.id.fullName);
        editTextAge = (EditText) findViewById(R.id.age);
        editTextEmail = (EditText) findViewById(R.id.email);
        editTextPassword = (EditText) findViewById(R.id.password);

        progressBar = (ProgressBar) findViewById(R.id.progressBar);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.banner:
                startActivity(new Intent(this, MainActivity.class));
                break;
            case R.id.registerUser:
                registerUser();
                break;
        }
    }

    private void registerUser() {
        String email= editTextEmail.getText().toString().trim();
        String password= editTextPassword.getText().toString().trim();
        String fullName= editTextFullName.getText().toString().trim();
        String age= editTextAge.getText().toString().trim();

        if (fullName.isEmpty()){
            editTextFullName.setError("Nome necessário!");
            editTextFullName.requestFocus();
            return;
        }

        if (age.isEmpty()){
            editTextAge.setError("Idade necessária!");
            editTextAge.requestFocus();
            return;
        }

        if (!Patterns.EMAIL_ADDRESS.matcher(email).matches()){
            editTextEmail.setError("Insira um email válido!");
            editTextEmail.requestFocus();
            return;
        }

        if (password.isEmpty()){
            editTextPassword.setError("Senha necessária!");
            editTextPassword.requestFocus();
            return;
        }

        if (password.length() < 6){
            editTextPassword.setError("Senha precisa ter no minimo 6 caracteres!");
            editTextPassword.requestFocus();
            return;
        }

        progressBar.setVisibility(View.VISIBLE);
        mAuth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()){
                            User user = new User(fullName, age, email);

                            FirebaseDatabase.getInstance().getReference("Users")
                                    .child(FirebaseAuth.getInstance().getCurrentUser().getUid())
                                    .setValue(user).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    if (task.isSuccessful()){
                                        Toast.makeText(RegisterActivity.this, "Usuário criado com sucesso!", Toast.LENGTH_LONG).show();
                                        progressBar.setVisibility(View.GONE);

                                        //next video!
                                    }else {
                                        Toast.makeText(RegisterActivity.this, "Falha ao se registrar! Tente novamente!", Toast.LENGTH_LONG).show();
                                        progressBar.setVisibility(View.GONE);
                                    }
                                }
                            });
                        }else {
                            Toast.makeText(RegisterActivity.this, "Falha ao se registrar!", Toast.LENGTH_LONG).show();
                            progressBar.setVisibility(View.GONE);
                        }
                    }
                });
    }
}

Solution

The solution is to move your textview to your register activity layout.

   <TextView
    android:id="@+id/banner"
    android:layout_width="285dp"
    android:layout_height="45dp"
    android:text="Denu"
    android:textSize="40dp"
    android:gravity="center"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.496"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.176" />

You have placed your banner textview in your main activity layout which is the root cause of your problem.

Answered By - Danish