title: python kivy "key_error: pos_hint"
body: <p>i am new in kivy.</p>
  
  <p>i got this error over and over</p>
  
  <blockquote>
    <p>File "_event.pyx", line 255, in kivy._event.EventDispatcher.bind (kivy_event.c:3629)<br>
     KeyError: 'pos_hint'</p>
  </blockquote>
  
  <p>this is my code:</p>
  
  <pre><code>class RiegosBoxLayout(BoxLayout):
  
      def __init__(self, **kwargs):
          super(RiegosBoxLayout, self).__init__(**kwargs)
          self.orientation= "vertical"
          lb= Label(text= "Riegos programados", font_size= '30dp', bold= True, size_hint= (1, .10))       
          self.add_widget(lb)
          db= sqlite3.connect('../db/dbInvernadero.s3db')
          cursor = db.cursor()
          cursor.execute("select ID, descripcion from tbRiegos")
          la= ListAdapter(
                          data=["{}".format(i[1]) for i in cursor.fetchall()],
                          selection_mode='single', 
                          allow_empty_selection=False, 
                          cls= ListItemButton)
  
          #lv = ListView( item_strings=[str(i[1]) for i in cursor.fetchall()])
          self.add_widget(la) # if i pass lv, it goes ok
          db.close()
  
  
  class MainScreen(Screen):
  
      def __init__(self, **kwargs):
          super(MainScreen, self).__init__(**kwargs)
          tb_panel= TabbedPanel(do_default_tab=False, size_hint=(1,1), pos_hint= {'center_x': .5, 'center_y': .5})
          tabs= ["Operaciones", "Riegos", "Valvulas", "Radiacion", "Configuracion"]
  
          for tb in tabs:
  
              if (tb == "Riegos"):
                  tbi=TabbedPanelItem(text=tb)
                  tbi.add_widget(RiegosBoxLayout())
                  tb_panel.add_widget(tbi)
              else:
                  tb_panel.add_widget(TabbedPanelItem(text=tb))
  
          self.add_widget(tb_panel)
  
  class MainApp(App):
  
      def build(self):
          # Create the screen manager
          sm = ScreenManager()
          sc=MainScreen()
          sm.add_widget(sc)
          return sm
  
  if __name__ == '__main__':
      MainApp().run()
  </code></pre>