Escribir en un EditText tipo tarjeta de crédito

public class CreditCardInputFilter implements InputFilter {
  private Pattern mPattern;
  private static final int MAX_LENGTH = 19;

  public CreditCardInputFilter() {
    mPattern = Pattern.compile("[0-9]{0,19}");
  }

  @Override
  public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < dest.length(); i++) {
      char c = dest.charAt(i);
      if (Character.isDigit(c)) {
        builder.append(c);
      }
    }
    Matcher matcher = mPattern.matcher(source);
    if (!matcher.matches()) {
      return dest.subSequence(dstart, dend);
    }

    builder.append(source);
    String result = builder.toString();
    if (result.length() <= MAX_LENGTH) {
      return source;