title: How can I make a map screen in kivy, I only get black screen
body: <pre><code>from kivy.app import App
  from kivy.lang import Builder
  from kivy.uix.textinput import TextInput
  from kivy.app import App
  from kivy.uix.widget import Widget
  from kivy.properties import StringProperty
  from kivy.properties import ObjectProperty
  from kivy.uix.label import Label
  from kivy.core.window import Window
  from kivy.uix.screenmanager import ScreenManager, Screen
  from kivy.uix.boxlayout import BoxLayout
  from kivy_garden.mapview import MapView
  </code></pre>
  <pre><code>kv = '''
  
  &lt;Login&gt;
      ben: benName.text
      pw: passwort.text
      knopf: btn
      knopff: btnn
   
      GridLayout:
          cols: 1
          size: root.width,root.height
          GridLayout:
              cols: 2
              Label:
                  text: &quot;Username&quot;
                  font_size: 25
              TextInput:
                  id: benName
                  multiline: False
                  font_size: 30
              Label:
                  text: &quot;Password&quot;
                  font_size: 25
                  bold: True
              TextInput:
                  password: True
                  id: passwort
                  multiline: False
                  font_size: 40
          Button:
              size_hint: (1.,1.10)
              text:&quot; Start &quot;
              id: btn
              font_size: 40
              on_release:
                  root.manager.current = &quot;Map&quot; if passwort.text == &quot;1&quot; and benName.text == &quot;1&quot; else &quot;login&quot;
                  root.manager.transition.direction = &quot;down&quot;
          Button:
              size_hint: (1.,1.10)
              text: &quot; Exit &quot;
              id: btnn
              font_size: 40
              on_release: app.stop()
  
  
  &lt;Map&gt;
      BoxLayout:
          Button:
              text: &quot; [back] &quot;
              bold: True
              font_size: 17
              size_hint: (None,None)
              width: 100
              height: 40
              on_release: app.stop()
  
  '''
  
  </code></pre>
  <p><code>MyApp</code> class:</p>
  <pre><code>class Login(Screen):
      ben = StringProperty()
      pw = StringProperty()
      knopf = ObjectProperty()
  
  
  class MyApp(App):
      Builder.load_string(kv)
   
      def build(self):
          ms = ScreenManager()
          ms.add_widget(Login(name='login'))
          ms.add_widget(Map(name='Map'))
          self.title = &quot;MyApp&quot;
          return ms
  
  
  
  
  
  
  class Map(Screen):
      def build(self):
          mapview = MapView(zoom=11, lat=50.6394, lon=3.057)
          return mapview
  
  
  if __name__ == '__main__':
      MyApp().run()
  </code></pre>