Android Studio getIntent from one activity but not from other

Issue

I have a question that whatever I search i can't find the answer for. So I have 3 Activities:StartActivity, LoginActivity and MainActivity In StartActivity I have 2 buttons: -Login - it sends me to LoginActivity -Continue as guest - it sends me to MainActivity In Login activity i have:

 login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    if(loginUser(false)) {
                        String username = String.valueOf(userName);

                        Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                        intent.putExtra("USERNAME", username);
                        startActivity(intent);
                        finish();
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        });

and in MainActivity I have :

private String username = getIntent().getStringExtra("USERNAME");

But when I try to login as guest the String username has nothing to get and gives me error. So how can I make String username getIntent only when I open the activity from LoginActivity and don't do anything when I open it from ContinueAsGuest button in StartActivity?

Solution

button in StartActivity only take you as guest right?if so code will look like this

guestBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    
                        String username = String.valueOf(userName);

                        Intent intent = new Intent(StartActivity.this, MainActivity.class);
                        intent.putExtra("USERNAME", username);
                        startActivity(intent);
                        finish();
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            
        });

Answered By - androidLearner