在EditText的xml屬性裡面添加了android:inputType=”number|numberDecimal” 小數或者小數點

//數量監聽
viewHolder.quantity.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

        }

        @Override
        public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {

        }

        @Override
        public void afterTextChanged(Editable editable) {
            String editStr = editable.toString().trim();

            int posDot = editStr.indexOf(".");
            //不允許輸入3位小數,超過三位就刪掉
            if (posDot < 0) {
                return;
            }
            if (editStr.length() - posDot - 1 > 2) {
                editable.delete(posDot + 3, posDot + 4);
            } else {
                //TODO...在這裡寫邏輯
            }
        }
    });