How to move text upwards on the screen every time a button is pressed

Question

I want to develop a chatting application for android. It will receive messages from the controller on the site. For this i have started designing a GUI. After practicing and

Answer 1

Chat App - Suggestion

Kivy Label » Text alignment and wrapping

• Declare a custom widget with inheritance of Label widget so that you can control the text alignment i.e. left for text sent, and right for text received.

Snippets - kv file

:
    size_hint_y: None
    text_size: self.width, None
    height: self.texture_size[1]
    halign: 'left'
    valign: 'middle'

Kivy RecycleView

• Replace Label: with RecycleView:
• Use CustomLabel as the viewclass
• Append text sent or text received to RecycleView's data

Snippets - kv file

RecycleView:
    id: rv
    viewclass: 'CustomLabel'

    RecycleBoxLayout:
        default_size_hint: 1, None
        orientation: 'vertical'

Kivy RecycleView » data

The view is generatad by processing the data, essentially a list of dicts, and uses these dicts to generate instances of the viewclass as required.

data

The data used by the current view adapter. This is a list of dicts whose keys map to the corresponding property names of the viewclass.

data is an AliasProperty that gets and sets the data used to generate the views.

Snippets - Py file

    def display_txt(self):
        self.ids.rv.data.append({'text': self.ids.txt.text, 'halign': 'left'})
        self.ids.txt.text = ''

Example

main.py

from kivy.app import App
from kivy.uix.screenmanager import Screen
from kivy.lang import Builder


class SMS(Screen):
    def send_txt(self):
        self.ids.rv.data.append({'text': self.ids.txt.text, 'halign': 'left'})
        self.ids.txt.text = ''

    def receive_txt(self):
        self.ids.rv.data.append({'text': self.ids.txt.text, 'halign': 'right'})
        self.ids.txt.text = ''


Builder.load_file("main.kv")


class MyApp(App):
    def build(self):
        return SMS()


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

main.kv

:
    size_hint_y: None
    text_size: self.width, None
    height: self.texture_size[1]
    halign: 'left'
    valign: 'middle'

:
    GridLayout:
        cols : 1

        BoxLayout:
            size_hint: 1, 0.1
            Button:
                text : 'Send'
                on_press : root.send_txt()
            Button:
                text : 'Receive'
                on_press : root.receive_txt()

        TextInput:
            hint_text : 'Write here'
            id : txt
            size_hint : .8 , .1
            pos : 0 ,0

        RecycleView:
            id: rv
            viewclass: 'ChatBox'

            RecycleBoxLayout:
                default_size_hint: 1, None
                orientation: 'vertical'

Output