adding widget dynamically into kivy screen object
<p>As far as I am aware, kv language is useful when making a static display, e.g. not when making game which need much widget's positioning during runtime. Here I try to make a simple game, but still need much positioning, so kv language is out of context for the widget, but not for the screen. I use screen to differentiate the main menu and game screen. But when I try to use 'add_widget' to insert my image, it always positioned at the middle of the window. Later I found out that the screen size is only 100x100. </p>

<p>Below are the only way that I can thought of, but still with no luck:</p>

<pre><code>class HomeScreen(Screen):
    pass

class GameScreen(Screen):
    pass

class ScreenManagement(ScreenManager):
    pass

presentation=Builder.load_file('ProjectSD.kv')

class ProjectSDApp(App):
    def build(self):
        A=presentation
        A.screens[0].size=(Window.size)
        A.screens[0].add_widget(Label(text='hello',font_Size=80,pos=(0,0)))
        return A

if __name__=='__main__':
    print(Window.size)
    ProjectSDApp().run()
</code></pre>

<p>and my ProjectSD.kv file:</p>

<pre><code>#: import FadeTransition kivy.uix.screenmanager.FadeTransition
ScreenManagement:
    transition: FadeTransition()
    HomeScreen:
    GameScreen:
&lt;Button&gt;:
    font_name:'attackofthecucumbers.ttf'

&lt;HomeScreen&gt;:
    name:'home'
    canvas:
        Rectangle:
            pos: self.pos
            size: self.size
            source: 'nature.jpg'
    Label:
        text: 'Monopoly GX'
        font_name:'KBDunkTank.ttf'
        font_size:100
        size_hint:0.7,0.2
        pos:root.width*0.15,root.height*0.70
    Button:
        on_release: app.root.current = "game"
        text: 'Play Game'
        font_size:root.width/20
        size_hint:0.3,0.15
        pos:root.width*0.35,root.height*0.45
    Button:
        on_release: app.stop()
        text: 'exit'
        font_size:root.width/20
        size_hint:0.3,0.15
        pos:root.width*0.35,root.height*0.20

&lt;GameScreen&gt;:
   name:'game'
   Button:
      on_release: app.root.current = "home"
      background_color: (1,0.15,0.2,0.8)
      text: 'X'
      font_size:root.width/40
      size_hint:0.05,0.05
      pos:root.width*0.95,root.height*0.95
</code></pre>

<p>Since there is no 'pos' method in screen object, I put my widget to position (0,0) manually.</p>

<p>The only way I found is just below:
<a href="https://kivyspacegame.wordpress.com/2014/08/10/tutorial-flappy-ship-part-2-build-simple-menus-and-animate-your-games-using-clock/" rel="nofollow noreferrer">https://kivyspacegame.wordpress.com/2014/08/10/tutorial-flappy-ship-part-2-build-simple-menus-and-animate-your-games-using-clock/</a></p>

<p>So my question is, if I use screen object from kivy's build in, how to achieve the same result? So I can still adding and remove widget as I want it later?</p>