title: display item selected from recycleview in label kivy
body: <p>i want to print the value selected from my list in to label but when i clicked in this list i have a message error :<br>
  <code>selected = self.ids.op_selected File "kivy\properties.pyx", line 863, in kivy.properties.ObservableDict.__getattr__
   AttributeError: 'super' object has no attribute '__getattr__'</code></p>
  
  <p>this my py</p>
  
  <pre><code>class RVItem(Factory.Button):
      def get_data_index(self):
  
          return self.parent.get_view_index_at(self.center)
      def on_press(self):
          print(self.get_data_index())
          selected = self.ids.op_selected
          selected.text = self.text
  
  class SecondWindow(BoxLayout, Screen):
      myresult = ListProperty([("liste_des_operations_id","PART_NO","Operation__NO","OPERATION_DESCRIPTION")])
  
      def insert_part(self):
          partnum = self.ids.Part_field
          part = partnum.text
  
          mycursor.execute(
              "SELECT * FROM liste_des_operations WHERE PART_NO = %s",
              (part,))
          self.myresult = mycursor.fetchall()
  </code></pre>
  
  <p>kv </p>
  
  <pre><code>    BoxLayout:
          orientation:'vertical'
  
          RecycleView:
              id: list_des_operation
              data: [{'text':"{}".format(OPERATION_DESCRIPTION)} for liste_des_operations_id,PART_NO,Operation__NO,OPERATION_DESCRIPTION in root.myresult]
              viewclass: "RVItem"
              text_selected: ""
              RecycleBoxLayout:
                  default_size: None, dp(56)
                  orientation: "vertical"
                  default_size_hint: 1, None
                  size_hint_y: None
                  height: self.minimum_height
                  key_selection: 'selectable'
                  multiselect: True
                  touch_multiselect: True
  
  
          Label:
              id: op_selected
              text: "op" 
  </code></pre>