only allow numbers android

import android.text.InputFilter
import android.text.Spanned

class NumberInputFilter : InputFilter {
    override fun filter(
        source: CharSequence?,
        start: Int,
        end: Int,
        dest: Spanned?,
        dstart: Int,
        dend: Int
    ): CharSequence? {
        source?.let {
            val filtered = StringBuilder()
            for (i in start until end) {
                if (Character.isDigit(source[i])) {
                    filtered.append(source[i])
                }
            }
            return filtered.toString()
        }
        return null
    }
}

This Kotlin code creates a custom InputFilter for an Android app that allows only numeric input. The NumberInputFilter class implements the InputFilter interface. Inside the filter function, it examines the input characters and only allows digits to pass through, filtering out any non-numeric characters.