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

cleaner version of @Ario's answer which follows the DRY principle:

private int prevCount = 0;
private boolean isAtSpaceDelimiter(int currCount) {
    return currCount == 4 || currCount == 9 || currCount == 14;
}

private boolean shouldIncrementOrDecrement(int currCount, boolean shouldIncrement) {
    if (shouldIncrement) {
        return prevCount <= currCount && isAtSpaceDelimiter(currCount);
    } else {
        return prevCount > currCount && isAtSpaceDelimiter(currCount);
    }
}

private void appendOrStrip(String field, boolean shouldAppend) {
    StringBuilder sb = new StringBuilder(field);
    if (shouldAppend) {
        sb.append(" ");
    } else {
        sb.setLength(sb.length() - 1);
    }
    cardNumber.setText(sb.toString());
    cardNumber.setSelection(sb.length());
}

ccEditText.addTextChangedListener(new TextWatcher() { 
    @Override 
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {

    } 

    @Override 
    public void onTextChanged(CharSequence s, int start, int before, int count) {

    } 

    @Override 
    public void afterTextChanged(Editable s) {
        String field = editable.toString();
        int currCount = field.length();

        if (shouldIncrementOrDecrement(currCount, true)){
            appendOrStrip(field, true);
        } else if (shouldIncrementOrDecrement(currCount, false)) {
            appendOrStrip(field, false);
        }
        prevCount = cardNumber.getText().toString().length(); 
    } 
});