The NumericTextBox depends on the HTML Input keydown
events in order to restrict user input, allowing only numeric characters. In some old devices / mobile OS, those events are not triggered correctly, hence the widget cannot validate the user input.
The widget seems to work in iPhone using iOS v9+:
(no characters are allowed)
(only numeric values are allowed)
The Android OS seems to allow any characters, which seems to be related to the Chrome mobile browser, which does not trigger the required events properly (like the iOS 9).
I will log this limitation in our product backlog for further investigation. For now, you will need to use
<input type="number" />
in order to avoid this erroneous behavior.
Telerik by Progress