根据我收到的建议，以下是我想出的方法：将可选日期限制为仅当日和之后。这适用于GWT 2.1.1

final DateBox dateBox = new DateBox();
dateBox.addValueChangeHandler(new ValueChangeHandler<Date>()
{
    @Override
    public void onValueChange(final ValueChangeEvent<Date> dateValueChangeEvent)
    {
        if (dateValueChangeEvent.getValue().before(today()))
        {
            dateBox.setValue(today(), false);
        }
    }
});
dateBox.getDatePicker().addShowRangeHandler(new ShowRangeHandler<Date>()
{
    @Override
    public void onShowRange(final ShowRangeEvent<Date> dateShowRangeEvent)
    {
        final Date today = today();
        Date d = zeroTime(dateShowRangeEvent.getStart());
        while (d.before(today))
        {
            dateBox.getDatePicker().setTransientEnabledOnDates(false, d);
            d = nextDay(d);
        }
    }
});

为了完整static起见，以下是处理日期的辅助方法：

private static Date today()
{
    return zeroTime(new Date());
}

/** this is important to get rid of the time portion, including ms */
private static Date zeroTime(final Date date)
{
    return DateTimeFormat.getFormat("yyyyMMdd").parse(DateTimeFormat.getFormat("yyyyMMdd").format(date));
}

private static Date nextDay(final Date date)
{
    return zeroTime(new Date(date.getTime() + 24 * 60 * 60 * 1000));
}