Android reverse money input with fixed decimal

Question

I want to create an Eddittext to type in currency values with 2 decimals from left to right. If there´s no value it shows 0.00, and as the user types the text should change acording to these rules:

I´ve tried getting it done using TextWatcher like in a similar question but I couldnt get it done as it kept calling TextWatcher after updating the text.

Answer 1

I finally got it working just as I wanted using a TextWatcher with this code, hope it helps someone:

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            if ((count - before) > 0) {
                String text = s.toString().replace(',', '.');
                text = text.replace("..", ".");
                if (text.equals(".")) {
                    text = "0,00";
                    amount_field.setText(text);
                    amount_field.setSelection(2);

                } else {
                    int counter = 0;
                    for (int i = 0; i < text.length(); i++) {
                        if (text.charAt(i) == '.') {
                            counter++;
                            if (counter > 1) {
                                break;
                            }
                        }
                    }

                    if (counter > 1) {
                        StringBuilder sb = new StringBuilder(text);
                        sb.deleteCharAt(start);
                        amount_field.setText(sb.toString().replace('.', ','));
                        amount_field.setSelection(start);

                    } else {
                        Float value = Float.valueOf(text);
                        String result = String.format("%.2f", value);
                        amount_field.setText(result.replace('.', ','));
                        if (start != result.length()) {
                            amount_field.setSelection(start + 1);
                        } else {
                            amount_field.setSelection(start);
                        }
                    }
                }
            }
        }