CODEWITHSUNDEEP
pythonkivy
danatron
danatron

Reputation: 717

Forcing kivy layout inside __init__

I've run into this problem several times, so either my approach is wrong or I missed a critical feature.

Frequently, I end up needing to set initial graphics information in a widgets init method. This doesn't work because when kivy graphics are first created they are at pos:0, 0 and size:100, 100. So whatever setup in init doesn't look correct.

Is there a way to force kivy to layout in a widgets init? I see the do_layout, but haven't figured out how to get to the layout to try it.

Here is an example:

Python:

class Main(Widget):
    route = ListProperty([])

    def __init__(self, *args, **kwargs):
        super(Main, self).__init__(**kwargs)
        self.route = [0, 0, self.width, self.height]


class RouteBuilderApp(App):
    def build(self):
        main = Main()
        return main

if __name__ == "__main__":
    RouteBuilderApp().run()

Kv:

<Main>
    canvas:
        Color:
            rgb: 0, 0, 0
        Rectangle:
            size: self.size
            pos: self.pos
        Color:
            rgb: 0, 0, 1
        Line: 
            points: root.route
            width: 2

Output:

enter image description here

Upvotes: 0

Views: 388

Answers (1)

kitti
kitti

Reputation: 14794

You need to use property binding. This is super simple in kv language, you can just change your kv like so:

canvas:
    Color:
        rgb: 0, 0, 0
    Rectangle:
        size: self.size
        pos: self.pos
    Color:
        rgb: 0, 0, 1
    Line: 
        points: 0, 0, root.width, root.height
        width: 2

By binding the points of the Line directly, you don't even need the intermediate route property.

Upvotes: 1

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