Error: Caused by: java.lang.NullPointerException

Question

I have an error which says:

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.example.pc.proyectofinal.SignUp.onCreate(SignUp.java:46)

I tried two ways:

• First with:

  Intent SignUpINTENT = new Intent(SignUp.this, ResetPassword.class);
           startActivity(SignUpINTENT);
  

• And the second time with:

  startActivity(new Intent(SignUp.this, ResetPassword.class));
  

Both give me the same error.

Here is the code:

public class SignUp extends AppCompatActivity {

    private EditText inputEmail, inputPassword;     //hit option + enter if you on mac , for windows hit ctrl + enter
    private Button btnSignIn, btnSignUp, btnResetPassword;
    private ProgressBar progressBar;
   private FirebaseAuth auth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       // setContentView(R.layout.activity_signup);
        //Get Firebase auth instance
        auth = FirebaseAuth.getInstance();

        btnSignIn = (Button) findViewById(R.id.sign_in_button);
        btnSignUp = (Button) findViewById(R.id.sign_up_button);
        inputEmail = (EditText) findViewById(R.id.email);
        inputPassword = (EditText) findViewById(R.id.password);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        btnResetPassword = (Button) findViewById(R.id.btn_reset_password);

        btnResetPassword.setOnClickListener(new View.OnClickListener() { //here is the problem with the regist
            @Override
            public void onClick(View v) {
                Intent SignUpINTENT = new Intent(SignUp.this, ResetPassword.class);
                startActivity(SignUpINTENT);
                //startActivity(new Intent(SignUp.this, ResetPassword.class));
            }
        });

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

        btnSignUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String email = inputEmail.getText().toString().trim();
                String password = inputPassword.getText().toString().trim();

                if (TextUtils.isEmpty(email)) {
                    Toast.makeText(getApplicationContext(), "Enter email address!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (TextUtils.isEmpty(password)) {
                    Toast.makeText(getApplicationContext(), "Enter password!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (password.length() < 6) {
                    Toast.makeText(getApplicationContext(), "Password too short, enter minimum 6 characters!", Toast.LENGTH_SHORT).show();
                    return;
                }

                progressBar.setVisibility(View.VISIBLE);
                //create user
                auth.createUserWithEmailAndPassword(email, password)
                        .addOnCompleteListener(SignUp.this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                Toast.makeText(SignUp.this, "createUserWithEmail:onComplete:" + task.isSuccessful(), Toast.LENGTH_SHORT).show();
                                progressBar.setVisibility(View.GONE);
                                // If sign in fails, display a message to the user. If sign in succeeds
                                // the auth state listener will be notified and logic to handle the
                                // signed in user can be handled in the listener.
                                if (!task.isSuccessful()) {
                                    Toast.makeText(SignUp.this, "Authentication failed." + task.getException(),
                                            Toast.LENGTH_SHORT).show();
                                } else {
                                    startActivity(new Intent(SignUp.this, Main.class));
                                    finish();
                                }
                            }
                        });

            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        progressBar.setVisibility(View.GONE);
    }
}

Answer 1

You have this line in onCreate() commented:

setContentView(R.layout.activity_signup);

Why?
Without this line there is no layout inflated for the activity and all the views can't be found by findViewById and they are null.
So when you try

btnResetPassword.setOnClickListener() 

you get

java.lang.NullPointerException