Only one root object is allowed by .kv

[Nightslayer Neptune]

I wanna to hide a Label, when the button is pressed.

Then release it when another button is pressed.

(NOW, i AM JUST DOING THE FIRST PART: HIDING)

This is my .kv

 10 Button:
 11     size_hint_y: .1
 12     size_hint_x: .1
 13     on_press: root.label.visible = False
 14 Label:
 15     id: label
 16     visible: True
 17     size_hint_x: 1 if self.visible else 0
 18     opacity: 1 if self.visible else 0
 19     disabled: not self.visible

and this is my python file

  1 from kivy.uix.button import Button
  2 from kivy.app import App
  3 from kivy.uix.screenmanager import ScreenManager, Screen
  4 class HelloApp(App):
  5     pass
  6
  7 if __name__ == '__main__':
  8     HelloApp().run()

when i run it it said 

Only one root object is allowed by .kv

[Elliot Garbus]

 

In your KV file there can be only one root widget.  The class instances, Button and Label are both on the far left, so each is root widget.

A solution is to organize them under a layout.  Now there is one root, the BoxLayout.

 

BoxLayout:

    Button:
         size_hint_y: .1
         size_hint_x: .1
         on_press: root.label.visible = False
    Label:
       id: label
        visible: True

        size_hint_x: 1 if self.visible else 0

        opacity: 1 if self.visible else 0

        disabled: not self.visible

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[Prabhat Mohanty]

Should not it be

 self.visible = True

?

--

[Nightslayer Neptune]

After I changed to this.

When I tried to click the button, it said AttributeError: ‘BoxLayout’ object has no attribute ‘ label’

Elliot Garbus於 2019年6月25日星期二 UTC-4下午8時11分22秒寫道：

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[Nightslayer Neptune]

Which sentence you mean??

Prabhat Mohanty於 2019年6月26日星期三 UTC-4上午1時06分44秒寫道：

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