如何配置EditText的软键盘最初使用数字，但仍允许文本？

I want to let users input a postal code to my app. The common use case is the US zip code, which are composed solely of numbers, so I'd like to display the numeric keyboard initially in the soft input. However, not all postal codes are solely digits, so I still need users to be able to enter other characters.I want to let users input a postal code to my a