title: Python/Kivy : Form submit using enter key
body: <p>I am moving from one <code>TextInput</code> to another <code>TextInput</code> using <code>enter</code> key.<br/>
  I want to move from last <code>TextInput</code> to <code>Button</code> using <code>enter</code> key .When I press again enter key then should be call <code>root.abc()</code> function.<br/>
  Can someone tell me how to done it?</p>
  
  <h1>test.py</h1>
  
  <pre><code>from kivy.uix.screenmanager import Screen
  from kivy.app import App
  from kivy.core.window import Window
  
  Window.clearcolor = (0.5, 0.5, 0.5, 1)
  Window.size = (300, 100)
  
  class User(Screen):
  
      def abc(self):
          print('Test')
  
  class Test(App):
  
      def build(self):
          return self.root
  
  if __name__ == '__main__':
      Test().run()
  </code></pre>
  
  <h1>test.kv</h1>
  
  <pre><code>User:
      BoxLayout:
          orientation: "vertical"
  
          TextInput:
              id:test1
              focus : True
              text: ' '
              width: 100
              multiline: False
              on_text_validate: test2.focus = True
  
          TextInput:
              id:test2
              text: ' '
              width: 100
              multiline: False
              on_text_validate: test3.focus = True
  
          Button:
              id:test3
              text: 'Ok'
              on_press : root.abc()
  </code></pre>