How do I use InputFilter to limit characters in an

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 docs.

Answer 1

InputFilters are a little complicated in Android versions that display dictionary suggestions. You sometimes get a SpannableStringBuilder, sometimes a plain String in the source parameter.

The following InputFilter should work. Feel free to improve this code!

new InputFilter() {
    @Override
    public CharSequence filter(CharSequence source, int start, int end,
            Spanned dest, int dstart, int dend) {

        if (source instanceof SpannableStringBuilder) {
            SpannableStringBuilder sourceAsSpannableBuilder = (SpannableStringBuilder)source;
            for (int i = end - 1; i >= start; i--) { 
                char currentChar = source.charAt(i);
                 if (!Character.isLetterOrDigit(currentChar) && !Character.isSpaceChar(currentChar)) {    
                     sourceAsSpannableBuilder.delete(i, i+1);
                 }     
            }
            return source;
        } else {
            StringBuilder filteredStringBuilder = new StringBuilder();
            for (int i = start; i < end; i++) { 
                char currentChar = source.charAt(i);
                if (Character.isLetterOrDigit(currentChar) || Character.isSpaceChar(currentChar)) {    
                    filteredStringBuilder.append(currentChar);
                }     
            }
            return filteredStringBuilder.toString();
        }
    }
}

Answer 2

It's Right, the best way to go about it to fix it in the XML Layout itself using:

<EditText
android:inputType="text"
android:digits="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" />

as rightly pointed by Florian Fröhlich, it works well for text views even.

<TextView
android:inputType="text"
android:digits="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" />

Just a word of caution, the characters mentioned in the android:digits will only be displayed, so just be careful not to miss any set of characters out :)

Answer 3

if you want to include the white space in your input as well then add space in android:digit code as shown above.

It works fine for me even in version above android 4.0.

enjoy :)

Answer 4

In addition to the accepted answer, it is also possible to use e.g.: android:inputType="textCapCharacters" as an attribute of <EditText> in order to only accept upper case characters (and numbers).

Answer 5

I found this on another forum. Works like a champ.

InputFilter filter = new InputFilter() {
    public CharSequence filter(CharSequence source, int start, int end,
            Spanned dest, int dstart, int dend) {
        for (int i = start; i < end; i++) {
            if (!Character.isLetterOrDigit(source.charAt(i))) {
                return "";
            }
        }
        return null;
    }
};
edit.setFilters(new InputFilter[] { filter });

Answer 6

None of posted answers did work for me. I came with my own solution:

InputFilter filter = new InputFilter() {
    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        boolean keepOriginal = true;
        StringBuilder sb = new StringBuilder(end - start);
        for (int i = start; i < end; i++) {
            char c = source.charAt(i);
            if (isCharAllowed(c)) // put your condition here
                sb.append(c);
            else
                keepOriginal = false;
        }
        if (keepOriginal)
            return null;
        else {
            if (source instanceof Spanned) {
                SpannableString sp = new SpannableString(sb);
                TextUtils.copySpansFrom((Spanned) source, start, sb.length(), null, sp, 0);
                return sp;
            } else {
                return sb;
            }           
        }
    }

    private boolean isCharAllowed(char c) {
        return Character.isLetterOrDigit(c) || Character.isSpaceChar(c);
    }
}
editText.setFilters(new InputFilter[] { filter });