title: adding multiple widgets to a scrollview
body: <p>I am trying to get a scrollable table of widgets. Each row has a different input (given here by TextInput) but I have many more rows (12) than I have screen space so I am putting it within a ScrollView.</p>
  
  <p>The problem is with the code below I get the following error.</p>
  
  <pre><code> kivy.uix.widget.WidgetException: Cannot add &lt;kivy.uix.boxlayout.BoxLayout object at 0x10e0abf30&gt;, it already has a parent &lt;kivy.uix.floatlayout.FloatLayout object at 0x10e0abfa0&gt;
  </code></pre>
  
  <p>My guess is because you can't add multiple widgets to a layout without giving them all unique ids? I'm stuck as to why <code>main.add_widget(row_layout)</code> does not allow you to iterate as many times as needed?</p>
  
  <pre><code>.kv
  
  ScrollView:
      do_scroll_x: False
          MyWidget:
  </code></pre>
  
  <p>My widget looks as follows:</p>
  
  <pre><code>within .py
  
  class MyWidget(BoxLayout):
  
  def __init__(self, **kwargs):
      super(MyWidget, self).__init__(**kwargs)
  
      col1 = TextInput()
      col2 = TextInput()
      col3 = TextInput()
      col4 = TextInput()
      col5 = TextInput()
      col6 = TextInput()
      col7 = TextInput()
      col8 = TextInput()
      cols = [col1,col2,col3,col4,col5,col6,col7,col8]
  
      row_layout = BoxLayout(orientation='horizontal')
      print("Constructing row...")
      for col in cols:
          print col
          row_layout.add_widget(col)
  
      print("Iterating through rows...")
      main = FloatLayout(orientation='vertical')
      for row in range(12):
          print("adding...",row)
          main.add_widget(row_layout)
  
      self.add_widget(main)
  </code></pre>