title: Freezing screen in kivy
body: <p>I got kivy label that I am updating in other class(not app or something) from another function
  by this code:</p>
  <pre><code>App.get_running_app().root.screens[3].fingerSensorStatus = &quot;Place Finger&quot;
  </code></pre>
  <p>fingerSensorStatus variable is text that in the kv file looks like</p>
  <pre><code>Label:
              pos_hint: {'x': 0.3 , 'y': 0.6 }
              text: root.fingerSensorStatus
              font_size: 40
              size_hint: 0.4, 0.4
  </code></pre>
  <p>This cause to my screen to freeze and turning it to black.
  So I saw this solution in the App class:</p>
  <pre><code>class AddFingerWindow(Screen):
  
      namee = ObjectProperty(None)
      passwd = ObjectProperty(None)
      fingerSensorStatus = StringProperty(&quot;&quot;)
      
      
      Clock.schedule_interval(self.callback, 1)
  
      def callback(self):
          fingerSensorStatus = db.FsensorStatus
  </code></pre>
  <p>But I am getting</p>
  <p>&quot;NameError: name 'self' is not defined&quot;</p>
  <p>Ive tried to solve it with:</p>
  <pre><code>def __init__(self):
          namee = ObjectProperty(None)
          passwd = ObjectProperty(None)
          fingerSensorStatus = StringProperty(&quot;&quot;)
          Clock.schedule_interval(self.callback, 1)
  </code></pre>
  <p>but got <strong>init</strong>() got an unexpected keyword argument 'name'.</p>
  <p>How I can solve this(I mean the freezing screen)?</p>