kivy anchor layout not anchoring?

Question

I am trying to get the Label called "number" to show up directly over the center of the Ellipse. I have tried putting both in the same layout, in different layouts, in AnchorLayouts and RelativeLayouts, and I haven't been able to figure out how to to this.

Here's a test version of my python showing the same issue:

class BugTester(FloatLayout):
    def __init__(self):
        super().__init__()
        for i in range(1,6):
            temp  = GamePiece(5, "Red")
            temp.pos = (i*100,i*200)
            self.add_widget(temp)


class BugTestingApp(App):
    def build(self):
        return BugTester()

class GamePiece(ToggleButton):

    def __init__(self, number, color, **kwargs):
        self.number = number
        self.player_color = color
        self.background_normal = "5.png"
        super(GamePiece, self).__init__()


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

And my kivy:

<BugTester>:
    Button:
        background_disabled_normal: "background.jpg"
        disabled: True


<GamePiece>:
    id: gamepiece
    size_hint:(None, None)
    group: self.player_color
    border: (0,0,0,0)


    AnchorLayout:
        id: layout
        center: root.center
        on_size: self.size = root.size
        anchor_x: "left"
        anchor_y: "bottom"

        canvas:
            Color:
                rgba: 0,0,0,1
            Ellipse:
            #this is the ellipse in question
                id: circle
                size: (root.width/2.5, root.height/3)
                #pos: -15, -20
                pos: root.pos

        Label:
        #this is the label I want centered over the ellipse
            id: number
            text: str(root.number)
            color: (1,1,1,1)
            font_size: root.height/4
            bold: True
            #pos: root.pos

Here's what it currently looks like: (one of the togglebuttons is pressed for illustration purposes)

Answer 1

In your example, labels are as big as the anchor layouts they belong to, so you can't move them.

If you want them to have some other size, then disable size_hint, and use a fixed size (for instance, as big as the ellipses):

Label:
#this is the label I want centered over the ellipse
    size_hint: None, None
    size: (root.width/2.5, root.height/3)
    id: number
    text: str(root.number)
    color: (1,1,1,1)
    font_size: root.height/4
    bold: True
    #pos: root.pos

Result: