Java 代码未在 Android Studio 中开始新活动？ 和上下文有关吗？

Question

Here is the code:

public void check(View button){ //checks if user's username and password correct
    String usernameInput;
    String passwordInput;

    usernameInput = ((EditText)findViewById(R.id.username)).getText().toString(); //gets user inputs as strings
    passwordInput = ((EditText)findViewById(R.id.password)).getText().toString();

    Log.d("username input", usernameInput);
    Log.d("password input", passwordInput);

    if (usernameInput == "user" && passwordInput == "password123") { //checks if correct
        correct(usernameInput);
    }
    else incorrect(button);
}


public void correct(String usernameInput) { //if correct, launches the main activity (main menu) through an intent (see below)
    Intent i = new Intent(this, MainActivity.class);
    i.putExtra("username", usernameInput); //passes data from LoginRegister activity to MainActivity
    startActivity(i);
}

I am trying to create a login system. Basically, when a button is clicked the 'check' method is called. The user inputs from 2 text boxes are checked to see if they're the correct username and password; if they are, the 'correct' method is called. It works fine up until this point, but for some reason the new activity just is not starting (no errors, it just doesn't start). I have tried putting all sorts for the context in the line Intent i = new Intent(this, MainActivity.class); , but nothing seems to work. Please help.

Answer 1

You should use equals instead of == .

== should be used during reference comparison. == checks if both references points to same location or not. On the other hand, equals() method should be used for content comparison. equals() method evaluates the content to check the equality.

So you should change your code to:

public void check(View button){ //checks if user's username and password correct
    String usernameInput;
    String passwordInput;

    usernameInput = ((EditText)findViewById(R.id.username)).getText().toString(); //gets user inputs as strings
    passwordInput = ((EditText)findViewById(R.id.password)).getText().toString();

    Log.d("username input", usernameInput);
    Log.d("password input", passwordInput);

    if (usernameInput.equals("user") && passwordInput.equals("password123")) { //checks if correct
        correct(usernameInput);
    }
    else incorrect(button);
}