Problem This is the code for register activity and i want to make user register and also add user name and user id details in realtimedatabase. But app gets crashed after opening register activity
Error
FATAL EXCEPTION: main
Process: com.example.movies4u, PID: 18933
java.lang.NullPointerException: Attempt to invoke interface method 'void com.google.firebase.auth.FirebaseAuth$AuthStateListener.onAuthStateChanged(com.google.firebase.auth.FirebaseAuth)' on a null object reference
at com.google.firebase.auth.zzl.run(com.google.firebase:firebase-auth@@21.0.3:1)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:7081)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:604)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:928)
Java
package com.example.movies4u;
import static android.content.ContentValues.TAG;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import com.example.movies4u.Utils.FirebaseMethods;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseAuthUserCollisionException;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
public class activity_register extends AppCompatActivity {
TextView HaveAccount;
EditText inputUsername,inputEmail,inputPassword,inputConfirmPassword;
String username,email,password;
Button btnRegister;
FirebaseAuth mAuth;
ProgressBar pb;
private String userID;
private FirebaseAuth.AuthStateListener mAuthListener;
private FirebaseMethods firebaseMethods;
private FirebaseDatabase mFirebaseDatabase;
private DatabaseReference myRef;
private String append;
@SuppressLint("MissingInflatedId")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN); //Hide status Bar
setContentView(R.layout.activity_register);
firebaseMethods =new FirebaseMethods(activity_register.this);
HaveAccount= (TextView) findViewById(R.id.HaveAccount);
pb = findViewById(R.id.progressBar3);
inputUsername=findViewById(R.id.inputUsername);
inputEmail=findViewById(R.id.inputEmail);
inputPassword=findViewById(R.id.inputPassword);
inputConfirmPassword=findViewById(R.id.inputConfirmPassword);
btnRegister=findViewById(R.id.btnRegister);
username=inputUsername.getText().toString();
email=inputEmail.getText().toString();
password=inputPassword.getText().toString();
pb.setVisibility(View.GONE);
HaveAccount.setOnClickListener(view -> {
Intent loginintent=new Intent(activity_register.this,login_activity.class);
startActivity(loginintent);
});
mAuth=FirebaseAuth.getInstance();
btnRegister.setOnClickListener(view -> ValidateDataandDoRegister());
}
private void ValidateDataandDoRegister() {
String username=inputUsername.getText().toString().trim();
String email=inputEmail.getText().toString().trim();
String password=inputPassword.getText().toString().trim();
String confirmPassword=inputConfirmPassword.getText().toString().trim();
if(email.isEmpty()){
inputEmail.setError("Enter Email Address");
inputEmail.requestFocus();
pb.setVisibility(View.GONE);
}
else if(email.length()<10){
inputEmail.setError("Enter valid Email");
inputEmail.requestFocus();
pb.setVisibility(View.GONE);
}
else if(password.isEmpty()){
inputPassword.setError("Enter the password");
inputPassword.requestFocus();
pb.setVisibility(View.GONE);
}
else if(password.length()<8){
inputPassword.setError("Password should be greater than 8 characters");
inputPassword.requestFocus();
pb.setVisibility(View.GONE);
}
else if(confirmPassword.isEmpty()){
inputConfirmPassword.setError("Re-Enter the Password");
inputConfirmPassword.requestFocus();
pb.setVisibility(View.GONE);
}
else if(confirmPassword.length()<8){
inputConfirmPassword.setError("Password should be greater than 8 characters");
inputConfirmPassword.requestFocus();
pb.setVisibility(View.GONE);
}
else if(!password.equals(confirmPassword)){
inputPassword.setError("Password not matched");
inputPassword.requestFocus();
inputConfirmPassword.setError("Password not matched");
inputConfirmPassword.requestFocus();
inputPassword.setText("");
inputConfirmPassword.setText("");
pb.setVisibility(View.GONE);
}
else{
pb.setVisibility(View.VISIBLE);
doRegister(username,email,password);
}
}
private void doRegister(String username,String email, String password) {
pb.setVisibility(View.VISIBLE);
mAuth.createUserWithEmailAndPassword(email, password).addOnSuccessListener(task -> {
if(task != null ){
if(mAuth.getCurrentUser() != null){
userID=mAuth.getCurrentUser().getUid();
}
// firebaseMethods.registerNewEmail(username,email,password);
setupFirebaseAuth();
sendVerificationEmail();
// firebaseMethods.addNewUser(email, username);
}
}).addOnFailureListener(e -> {
if(e instanceof FirebaseAuthUserCollisionException){
btnRegister.setEnabled(true);
inputEmail.setError("Email Already Registered");
pb.setVisibility(View.GONE);
inputEmail.requestFocus();
}
else{
btnRegister.setEnabled(true);
pb.setVisibility(View.GONE);
Toast.makeText(activity_register.this, "Oops! Something Went wrong", Toast.LENGTH_SHORT).show();
}
});
}
private void sendVerificationEmail() {
mAuth.getCurrentUser().sendEmailVerification().addOnCompleteListener(task -> {
if(task != null && task.isSuccessful()){
btnRegister.setEnabled(true);
pb.setVisibility(View.GONE);
Toast.makeText(activity_register.this, "Email has been sent to your email address", Toast.LENGTH_SHORT).show();
//fixing the bug
mAuth.signOut();
}
else {
btnRegister.setEnabled(true);
pb.setVisibility(View.GONE);
Toast.makeText(getApplicationContext(), "Oops! failed to send verification email",Toast.LENGTH_SHORT).show();
}
});
}
/*
------------------------------------ Firebase ---------------------------------------------
*/
/**
* Setup the firebase auth object
*/
private void setupFirebaseAuth(){
Log.d(TAG, "setupFirebaseAuth: setting up firebase auth.");
mAuth = FirebaseAuth.getInstance();
mFirebaseDatabase = FirebaseDatabase.getInstance();
myRef = mFirebaseDatabase.getReference();
//cannot get into this part of code
mAuthListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user=firebaseAuth.getCurrentUser();
if (user != null) {
// User is signed in
Log.d(TAG, "onAuthStateChanged:signed_in:" user.getUid());
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
//1st check: Make sure the username is not already in use
if(firebaseMethods.checkIfUsernameExists(username, dataSnapshot)){
//to randomly generate key to make sure username is unique
append = myRef.push().getKey().substring(3,10);
Log.d(TAG, "onDataChange: username already exists. Appending random string to name: " append);
}
username = username append;
//add new user to the database
// firebaseMethods.addNewUser(email, username);
Toast.makeText(activity_register.this, "SignUp successful", Toast.LENGTH_SHORT).show();
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(activity_register.this, "unsuccessful", Toast.LENGTH_SHORT).show();
}
});
finish();
} else {
// User is signed out
Toast.makeText(activity_register.this, "unsuccessful", Toast.LENGTH_SHORT).show();
Log.d(TAG, "onAuthStateChanged:signed _out");
}
// ...
}
};
}
@Override
public void onStart() {
super.onStart();
mAuth.addAuthStateListener(mAuthListener);
}
@Override
public void onStop() {
super.onStop();
if (mAuthListener != null) {
mAuth.removeAuthStateListener(mAuthListener);
}
}
}
I am expecting to store the user data in a realtime database. But i am getting a null pointer exception after i enter into the register activity. I guess it is because of the null user. But i should get a non-null user, because i am implementing that method after the user clicking on the register button and after the all the fields are verified .
CodePudding user response：
Your code's flow is wrong. You're adding AuthListener in onStart() as mAuth.addAuthStateListener(mAuthListener); but you're initializing this mAuthListener later in the doRegiter(), which means while adding it in onStart(), it's not initialized and null which gives the error Null Pointer Exception.
For the solution, you should call the function setUpFirebaseAuth in onStart before adding it to the mAuth as:
@Override
public void onStart() {
super.onStart();
setupFirebaseAuth();
mAuth.addAuthStateListener(mAuthListener);
}