kivy reference text of TextInput by StringProperty

Question

I would like to get the text of my TextInput via a StringProperty, but it does not work. I get an empty string. In the second example, I am declaring the whole TextInput as an ObjectProperty and then it does work. What is wrong with my first example?

How can a StringProperty be used to define the text inside a TextInput?

First example does not print text of TextInput example1.py

from kivy.app import App
from kivy.base import Builder
from kivy.properties import StringProperty
from kivy.uix.boxlayout import BoxLayout

Builder.load_string("""
<rootwi>:
    orientation: 'vertical'
    Button:
        on_press: root.print_txt()
    TextInput:
        text: root.textinputtext
""")
class rootwi(BoxLayout):
    textinputtext = StringProperty()

    def print_txt(self):
        print(self.textinputtext)


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

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

Second example does print text of TextInput, but uses a ObjectProperty not StringProperty example2.py

from kivy.app import App
from kivy.base import Builder
from kivy.properties import ObjectProperty
from kivy.uix.boxlayout import BoxLayout
from kivy.clock import Clock


Builder.load_string("""
<rootwi>:
    txt: txt
    orientation: 'vertical'
    Button:
        on_press: root.print_txt()
    TextInput:
        id: txt
""")
class rootwi(BoxLayout):
    txt = ObjectProperty()

    def print_txt(self):
        print(self.txt.text)


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

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

If I set the text to sth specific, it shows up in the TextInput. (But still, cannot be printed)

from kivy.app import App
from kivy.base import Builder
from kivy.properties import StringProperty
from kivy.uix.boxlayout import BoxLayout

Builder.load_string("""
<rootwi>:
    orientation: 'vertical'
    Button:
        on_press: root.print_txt()
    TextInput:
        text: root.textinputtext
""")
class rootwi(BoxLayout):
    textinputtext = StringProperty()

    def __init__(self, **kwargs):
        self.textinputtext = 'palim'
        super(rootwi, self).__init__(**kwargs)

    def print_txt(self):
        print(self.textinputtext)


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

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

because this is a simplified example of a widget which is made up of multiple textinputs, labels, buttons all defined in the kv file. Normally I would stick to the second version, but I just do not get why I cannot work with the first one. — PalimPalim, Jun 19 '17 at 13:55
With `text: root.textinputtext` the text of the `TextInput` changes if the value of the `StringVariable` does, but not vice versa. — FJSevilla, Jun 19 '17 at 14:40
yes, I saw that as well, for example if you specify it in the init method to be a certain value, it will be there if you start the app. — PalimPalim, Jun 19 '17 at 15:06
Maybe you need to do some sort of binding. (I added what you pointed out to the question) — PalimPalim, Jun 19 '17 at 15:13

score 5 · Accepted Answer · answered Jun 19 '17 at 16:40

If you want set and get the text using the StringProperty then you should create a bidirectional bind:

from kivy.app import App
from kivy.base import Builder
from kivy.properties import StringProperty, ObjectProperty
from kivy.uix.boxlayout import BoxLayout


Builder.load_string("""
<rootwi>:
    orientation: 'vertical'
    textinputtext: txt.text
    Button:
        on_press: root.print_txt()
    TextInput:
        id: txt
        text: root.textinputtext
""")

class rootwi(BoxLayout):
    textinputtext = StringProperty()

    def __init__(self, **kwargs):
        super(rootwi, self).__init__(**kwargs)
        self.textinputtext = 'palim'

    def print_txt(self):
        print(self.textinputtext)



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

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

Output:

Thank you! That is a really nice answer. – PalimPalim Jun 20 '17 at 06:42 — PalimPalim, Jun 20 '17 at 06:42

kivy reference text of TextInput by StringProperty

How can a StringProperty be used to define the text inside a TextInput?

1 Answers1

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