STACK_ACTIVITY

class LoginActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
        goto_main_screen_button.setOnClickListener {
            gotoMainScreen()
        }
    }

    private fun gotoMainScreen() {
        val intent = Intent(this, MainActivity::class.java)
        startActivity(intent)
        finish()
    }
}


class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        goto_password_screen_button.setOnClickListener {
            gotoPasswordScreen()
        }
    }

    private fun gotoPasswordScreen() {
        val intent = Intent(this, PasswordActivity::class.java)
        startActivity(intent)
    }
}


class PasswordActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_password)
        goto_login_screen_button.setOnClickListener {
            gotoLoginScreen()
        }
    }

    private fun gotoLoginScreen() {
        val intent = Intent(this, LoginActivity::class.java)
        intent.flags = Intent.FLAG_ACTIVITY_CLEAR_TASK or Intent.FLAG_ACTIVITY_NEW_TASK
        startActivity(intent)
    }
}