I can't read the value of text input in Kivy

Question

My problem is when I want to display the value given by the user in the Text input text field.

When I want to get the text value from the input I get an empty value and I cannot display anything in the label field .

Here is my code :

• The kv file :

  • MainGridLayout:
    
    <MainGridLayout>:
    cols: 1
    rows: 2
    BoxLayout:
        orientation: 'vertical'
        TextInput:
            id: my_text_input
            text: root.text_input_1
            hint_text :'Operations'
            multiline:False
            pos_hint: {'center_x': 0.5, 'center_y': 0.705}
            size_hint: 0.95, 0.5
            font_size: '30dp'
        Label:
            text: root.Display_text
            font_size: '45dp'
    StackLayout:
        Button:
            text:"+"
            spacing: .2, .2
            size: 85, 85
            size_hint: None, None
            on_press: root.on_button_plus()
    
    

• The py file :

  • 
    from kivy.app import App
    from kivy.properties import StringProperty
    from kivy.uix.gridlayout import GridLayout
    
    
    # different layouts:
    
    class MainGridLayout(GridLayout):
    
         text_input_1 = StringProperty()
         Display_text = StringProperty()
    
         def on_button_plus(self):
             print(f'{self.text_input_1}')
    
    
         # run application:
    
         class CalculatorApp(App):
             pass
    
         CalculatorApp().run()
    

Answer 1

Actually, you don't need the variables text_input_1 and Display_text. To display the text from the my_text_input on the label you can add text: my_text_input.text instead of text: root.Display_text. Now, when the text of my_text_input changes, the label's text will change automatically and you don't need any functions. In on_button_plus() method you can do the same and print my_text_input's text using its text property (from all MainGridLayout's ids you take only my_text_input and print its text). The line text: root.text_input_1 unnecessary, too.

Here is my editted version of your code:

The .py file

from kivy.app import App
from kivy.properties import StringProperty
from kivy.uix.gridlayout import GridLayout


class MainGridLayout(GridLayout):

    def on_button_plus(self):
        print(f'{self.ids.my_text_input.text}')


class CalculatorApp(App):
    pass


CalculatorApp().run()

The .kv file

MainGridLayout:

<MainGridLayout>:
    cols: 1
    rows: 2
    BoxLayout:
        orientation: 'vertical'
        TextInput:
            id: my_text_input
            hint_text :'Operations'
            multiline:False
            pos_hint: {'center_x': 0.5, 'center_y': 0.705}
            size_hint: 0.95, 0.5
            font_size: '30dp'
        Label:
            text: my_text_input.text  # change the text automatically
            font_size: '45dp'
    StackLayout:
        Button:
            text:"+"
            spacing: .2, .2
            size: 85, 85
            size_hint: None, None
            on_press: root.on_button_plus()