Unfortunately, you can’t style it. The styles and styling attributes for NumberPicker
are not present in the public API, therefore you can’t set them and change the default look. You can only select between light and dark theme.
As a solution I would suggest to use android-numberpicker library instead. The library is basically a port of NumberPicker extracted from Android source codes. But it’s better than that, it also backports NumberPicker
to Android 2.x. The library can be easily styled.
To style the divider adjust NPWidget.Holo.NumberPicker
style and its selectionDivider
and selectionDividerHeight
attributes.
To style the text adjust NPWidget.Holo.EditText.NumberPickerInputText
style.