Allows number verification on MDTextfield

[Jo-e7]

This adds number verification functionality to MDTextField. Here is a demo of the functionality:

number_validator.mp4

The code used for the demo was:

from kivy.lang import Builder

from kivymd.app import MDApp

KV = '''
MDScreen:
    md_bg_color: app.theme_cls.surfaceColor

    MDTextField:
        mode: "outlined"
        size_hint_x: None
        pos_hint: {"center_x": .5, "center_y": .5}
        width: "240dp"
        validator: "number"
        MDTextFieldLeadingIcon:
            icon: "numeric"
        MDTextFieldHintText:
            text: "Insert a number"

'''


class Number_validator(MDApp):
    def build(self):
        return Builder.load_string(KV)


Number_validator().run()

[HeaTTheatR]

The code contains several problems:

• A logic error: the function returns True on the first non-digit, and False only if all characters are digits. This is the opposite of the typical behavior of is_number_valid (which usually returns True for valid numbers).
• An redundant break: the return already breaks the loop.
• An incorrect name: the function returns True on an error.

Easier:

def is_number_valid(self, text: str) -> bool:
    """Checks if the text contains only digits."""

    return text.isdigit()