How do I use InputFilter to limit characters in an EditText in Android?

Question

I want to restrict the chars to 0-9, a-z, A-Z and spacebar only. Setting inputtype I can limit to digits but I cannot figure out the ways of Inputfilter looking through the

Answer 1

You can specify wanted characters in a regex and use it in InputFilter:

val regex = Regex("[a-zA-Z\\d ]")
    
editText.filters = arrayOf(InputFilter { source, _, _, _, _, _ ->
    source.filter { regex.matches(it.toString()) }
})

Notice, I didn't used \w character class, because it includes underscore _

Answer 2

I have the same answer in Kotlin:

/**
 * Returns the filter of the editText'es CharSequence value when [filterType] is:
 * 1 -> letters; 2 -> letters and digits; 3 -> digits;
 * 4 -> digits and dots
 */
class InputFilterAlphanumeric(private val filterType: Int): InputFilter {
    override fun filter(source: CharSequence?, start: Int, end: Int, dest: Spanned?, dstart: Int, dend: Int): CharSequence {
        (source as? SpannableStringBuilder)?.let {sourceAsSpannableBuilder  ->
            for (i in (end - 1) downTo start) {
                val currentChar = source[i]
                when(filterType) {
                    1 -> {
                        if (!currentChar.isLetter() && !currentChar.isWhitespace()) {
                            sourceAsSpannableBuilder.delete(i, i + 1)
                        }
                    }
                    2 -> {
                        if (!currentChar.isLetterOrDigit() && !currentChar.isWhitespace()) {
                            sourceAsSpannableBuilder.delete(i, i + 1)
                        }
                    }
                    3 -> {
                        if (!currentChar.isDigit()) {
                            sourceAsSpannableBuilder.delete(i, i + 1)
                        }
                    }
                    4 -> {
                        if (!currentChar.isDigit() || !currentChar.toString().contains(".")) {
                            sourceAsSpannableBuilder.delete(i, i + 1)
                        }
                    }
                }
            }
            return source
        } ?: run {
            val filteredStringBuilder = StringBuilder()
            for (i in start until end) {
                val currentChar = source?.get(i)
                when(filterType) {
                    1 -> {
                        if (currentChar?.isLetter()!! || currentChar.isWhitespace()) {
                            filteredStringBuilder.append(currentChar)
                        }
                    }
                    2 -> {
                        if (currentChar?.isLetterOrDigit()!! || currentChar.isWhitespace()) {
                            filteredStringBuilder.append(currentChar)
                        }
                    }
                    3 -> {
                        if (currentChar?.isDigit()!!) {
                            filteredStringBuilder.append(currentChar)
                        }
                    }
                    4 -> {
                        if (currentChar?.isDigit()!! || currentChar.toString().contains(".")) {
                            filteredStringBuilder.append(currentChar)
                        }
                    }
                }
            }
            return filteredStringBuilder
        }
    }
}

and get the class with an Extension function:

fun EditText.filterByDataType(filterType: Int) {
    this.filters = arrayOf<InputFilter>(InputFilterAlphanumeric(filterType))
}