Codename One：PickerComponent日期年龄验证的跨Locale适配问题

Hey there, I see the issue you're facing—your current validator relies on a fixed date format (dd/mm/yy) which breaks when the device's locale changes, plus the two-digit year parsing is ambiguous and there's a subtle format bug. Let's fix this with a validator that adapts to the device's locale while ensuring accurate age calculation.

The Problem with Your Current Code #

• You’re hardcoding a date format that doesn’t match the locale-specific formatting the PickerComponent uses, so parsing fails when the locale changes.
• The mm in your format is for minutes, not months—you should use MM for months! This would already throw off your validation even if the locale matched.
• Two-digit year parsing can lead to incorrect dates (e.g., "03" might be interpreted as 1903 instead of 2003).

Fixed Locale-Adaptive Validator #

Here’s a revised version that handles locale-specific date strings correctly, fixes the month/minute mix-up, and ensures proper two-digit year handling:

PickerComponent datePicker = PickerComponent.createDate(new Date())
        .label("Data di nascita")
        .errorMessage("Hai almeno 13 anni?");

Validator validator = new Validator();
validator.addConstraint(datePicker, new Constraint() {
    @Override
    public boolean isValid(Object value) {
        if (!(value instanceof String)) {
            Log.p("Invalid input type: expected String");
            return false;
        }

        String inputDateStr = (String) value;
        Log.p("-----------------");
        Log.p("Inserted birthday date: " + inputDateStr);
        Log.p("-----------------");

        // Use the locale-specific short date formatter that matches the Picker's output
        DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.SHORT, Locale.getDefault());
        
        // Set a clear range for two-digit year parsing to avoid century confusion
        if (dateFormat instanceof SimpleDateFormat) {
            SimpleDateFormat sdf = (SimpleDateFormat) dateFormat;
            // Assume two-digit years refer to 1950-2049 (adjust this range if needed)
            sdf.set2DigitYearStart(new GregorianCalendar(1950, Calendar.JANUARY, 1).getTime());
        }

        try {
            Date birthdayDate = dateFormat.parse(inputDateStr);
            Calendar birthday = Calendar.getInstance();
            birthday.setTime(birthdayDate);

            Calendar nowMinus13 = Calendar.getInstance();
            nowMinus13.add(Calendar.YEAR, -13);

            // Check if the birthday is on or before the date 13 years ago
            return birthday.before(nowMinus13) || birthday.equals(nowMinus13);
        } catch (ParseException ex) {
            Log.p("Cannot parse the date: " + ex.getMessage());
            return false;
        }
    }

    @Override
    public String getDefaultFailMessage() {
        return "You must be at least 13 years old";
    }
});

Key Improvements #

• Locale Adaptability: Uses DateFormat.getDateInstance(DateFormat.SHORT, Locale.getDefault()) which automatically matches the short date format the PickerComponent uses for the current locale—no more hardcoding formats!
• Fixed Month Format: Eliminated the mm/MM mix-up that would have broken date parsing even in matching locales.
• Two-Digit Year Clarity: Sets an explicit range for two-digit year parsing to avoid incorrect century assumptions.
• Robust Input Checks: Added a check for non-string input to handle edge cases gracefully.

Bonus: Even Better Approach (If Possible) #

If you can configure the PickerComponent to return a Date object directly instead of a String, that would eliminate parsing issues entirely. Check the component’s documentation to see if there’s a setting for this—it’s the most reliable long-term solution.

内容的提问来源于stack exchange，提问作者Francesco Galgani