title: Wrong screen showing after start with ScreenManager
body: <p>I am trying to code a simple quiz game. There're supposed to be multiple screens, the first screen (LoginWindow) being a simple login form. After the login and confirmation of the right name and password being entered the second screen (GameWindow) is supposed to show up, but it doesn't. Right from the start the second screen is being loaded.
  I'm sure I am missing something super simple and basic but I just don't get it.</p>
  <p>.py file:</p>
  <pre><code>from kivy.app import App
  from kivy.properties import ObjectProperty
  from kivy.lang import Builder
  from kivy.core.window import Window
  from kivy.uix.screenmanager import ScreenManager, Screen
  import hashlib
  
  Window.size = (512, 512)
  
  user_hash = &quot;&quot;
  pass_hash = &quot;&quot;
  
  super_user = &quot;9279F4A7C1C145D5AE930FDA23EF386168F6720B4E0F0D3DEE383C5AD8535737&quot;
  super_pass = &quot;EE22032527082315A747781829EF1F9195F6AEAC09C0D52DE06EBF9D8C463918&quot;
  
  
  # Define screens
  class LoginWindow(Screen):
  
      name = ObjectProperty(None)
      passw = ObjectProperty(None)
  
      def press(self):
          user_hash = hashlib.sha256(self.name.text.encode('utf-8')).hexdigest().upper()
          pass_hash = hashlib.sha256(self.passw.text.encode('utf-8')).hexdigest().upper()
          if (user_hash == super_user) and (pass_hash == super_pass):
              print(&quot;Das hat geklappt!&quot;)
              WindowManager.current = 'game'
          else:
              print(&quot;Du kummst hier net rein!&quot;)
  
  
  class GameWindow(Screen):
      pass
  
  
  class WindowManager(ScreenManager):
      pass
  
  
  kv = Builder.load_file('box_multiscreen.kv')
  
  
  class Affenquiz(App):
  
      def build(self):
          Window.clearcolor = (0.8, 0.8, 0.8, 1)
          WindowManager = ScreenManager()
          WindowManager.add_widget(LoginWindow(name='login'))
          WindowManager.add_widget(GameWindow(name='game'))
          WindowManager.current = 'login'
  
          return kv
  
  
  if __name__ == &quot;__main__&quot;:
      Affenquiz().run()
  </code></pre>
  <p>.kv file:</p>
  <pre><code>WindowManager:
      LoginWindow:
          name: &quot;login&quot;
      GameWindow:
          name: &quot;game&quot;
  
  &lt;LoginWindow&gt;:
  
      name:name
      passw:passw
  
      BoxLayout:
          orientation: &quot;vertical&quot;
          size: root.width, root.height
  
          spacing: 20
          padding: 20
  
          canvas.before:
              Rectangle:
                  pos: self.pos
                  size: self.size
                  source: 'monkey.png'
  
          AnchorLayout:
              anchor_y: 'top'
              BoxLayout:
                  orientation: &quot;horizontal&quot;
                  size_hint: (1, None)
                  height: 50
  
                  Label:
                      text: &quot;Der Quizfelsen&quot;
                      font_size: 50
  
          BoxLayout:
              orientation: &quot;horizontal&quot;
              size_hint: (1, None)
              height: 50
  
              Label:
                  text: &quot;Benutzer:&quot;
              TextInput:
                  id: name
                  multiline:False
                  background_color: (241/255.0,241/255.0,241/255.0,0.9)
  
          BoxLayout:
              orientation: &quot;horizontal&quot;
              size_hint: (1, None)
              height: 50
  
              Label:
                  text: &quot;Passwort:&quot;
              TextInput:
                  id: passw
                  multiline:False
                  background_color: (241/255.0,241/255.0,241/255.0,0.9)
  
          RoundedButton:
              text: &quot;Login&quot;
              pos_hint: {'center_x': .5}
              size_hint: (1, None)
              height: 50
              on_press: root.press()
  
  &lt;GameWindow&gt;:
      Label:
          text: &quot;Der Quizfelsen&quot;
          font_size: 50
  
  &lt;Label&gt;
      font_size: 32
      background_normal: ''
      background_color: (0.9,0.9,0.9,0)
      canvas.before:
          Color:
              rgba: self.background_color
          Rectangle:
              size: self.size
              pos: self.pos
      color: (184/255.0,70/255.0,35/255.0,1)
      bold: True
      outline_color: (1,1,1,1)
      outline_width: 2
  
  &lt;RoundedButton@Button&gt;
      background_color: (0,0,0,0)
      background_normal: ''
      canvas.before:
          Color:
              rgba: (184/255.0,70/255.0,35/255.0,0.9)
          RoundedRectangle:
              size: self.size
              pos: self.pos
              radius: [25]
  </code></pre>
  <p>Thank you in advance</p>