android format edittext to display spaces after every 4 characters

Question

Android - I want to get a number input from the user into an EditText - it needs to be separated by spaces - every 4 characters. Example: 123456781234 -> 1234 5678 1234

Answer 1

Here is a little help function. For your example you would call it with

addPadding(" ", "123456781234", 4);

/**
 * @brief Insert arbitrary string at regular interval into another string 
 * 
 * @param t String to insert every 'num' characters
 * @param s String to format
 * @param num Group size
 * @return
 */
private String addPadding(String t, String s, int num) {
    StringBuilder retVal;

    if (null == s || 0 >= num) {
        throw new IllegalArgumentException("Don't be silly");
    }

    if (s.length() <= num) {
        //String to small, do nothing
        return s;
    }

    retVal = new StringBuilder(s);

    for(int i = retVal.length(); i > 0; i -= num){
        retVal.insert(i, t);
    }
    return retVal.toString();
}