Dynamically adjusting BoxLayout

[Carry White]

I'm trying to get an image into my Boxlayout. I want this image to fill all of the screen width and I want it to keep aspect ratio. In the remaing space at the bottom of the screen I want to have a button, which fills all of the remaining space. To illustrate what I'm trying to achive I made this little doodle:

So I want the img_width to be = screen_width.
I want the img_height to be the size it has to be, to keep aspect ratio.

I want the button width to be = screen_width
And I want the button height to take up the remaining height. So I want button_height = screen_height-button_height

I tried many things but I simple could not get what I want. This is an example of what I tried:

Code hier eingeben.from kivy.app import App

from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout

from kivy.uix.image import Image


class MainImage(BoxLayout):
    pass
       

class KommaApp(App):
    def build(self):
        a = MainImage()
        return a
   
if __name__ == '__main__':
    KommaApp().run()..

Code hier eingeben.
<MainImage@BoxLayout>:
    orientation: 'vertical'
    width: main_image.width
    height: main_image.height
    Image:
        id: main_image
        source: '02.jpg'
    Button:
        text: 'Button A'    
        ..

Any help on this would be appreciated :) Thanks

[ZenCODE]

Sorry for the late reply, but better late than never I hope? ;-)

So, I think this doe what you want.

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder


Builder.load_string('''
#<MainImage@BoxLayout>: #  No need to repeat the BoxLayout subclassing
<MainImage>:
    img: img
    btn: btn
    orientation: 'vertical'
    Image:
        id: img
        source: 'img1.png'
        size_hint: (None, None)
        allow_stretch: True
        keep_ratio: False

    Button:
        id: btn
        text: 'Button A'
        size_hint_y: None
''')


class MainImage(BoxLayout):

    def on_size(self, widget, size):
        self.img.size = (self.width, self.width * self.img.image_ratio)
        self.btn.height = self.height - self.img.height

class KommaApp(App):
    def build(self):
        a = MainImage()
        return a

if __name__ == '__main__':
    KommaApp().run()

It seems a bit awkward to me, and certainly not the best use of layouts. I would have thought this would work better, but then again, I have no idea what you are actually trying to do, so feel free to think me a petulant prat...;-)

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder


Builder.load_string('''
#<MainImage@BoxLayout>: #  No need to repeat the BoxLayout subclassing
<MainImage>:
    img: img
    btn: btn

    orientation: 'vertical'
    FloatLayout:
        Image:
            id: img
            source: 'img1.png'
            allow_stretch: True
            keep_ratio: False
            size_hint: (None, None)
            pos_hint: {"center_x": 0.5, "center_y": 0.5}

    Button:
        id: btn
        text: 'Button A'
        size_hint_y: None
        height: "30sp"
''')


class MainImage(BoxLayout):

    def on_size(self, widget, size):
        area_ratio = self.width / (self.height - self.btn.height)
        img = self.img
        if area_ratio < img.image_ratio:
            img.size = (self.width, self.width * img.image_ratio)
        else:
            img.size = (self.width / area_ratio,
                        self.height - self.btn.height)