title: Login System in Kivy
body: <p>I am new to Kivy, and I want to create a simple login system for desktop app.</p>
  
  <p>Here's my python code:</p>
  
  <pre><code>class LoginPage(Screen):
      pass
  class UserPage(Screen):
      pass
  class ScreenManagement(ScreenManager):
      pass
  
  kv_file = Builder.load_file('login.kv')
  class LoginApp(App):
      def builder(self):
          return kv_file
  
  LoginApp().run()
  </code></pre>
  
  <p>and kivy file</p>
  
  <pre><code>ScreenManagement:
      LoginPage:
      UserPage:
  &lt;LoginPage&gt;:
      name: "login_page"
      BoxLayout:
          TextInput:
              id: login
          TextInput:
              id: passw
          Button:
              text: "go"
              on_release: app.root.current = "user"
  &lt;UserPage&gt;:
      name: "user"
      Button:
          text: "back"
          on_release: app.root.current = "login_page"
  </code></pre>
  
  <p>I want it to change the screen only if text in form is what I need (e.g - TextInput(login) = 'username', TextInput(pass) = 'password').</p>
  
  <p>I know I need to write a method for this, but I need help with this.</p>