日期的剩余天数显示不正确

请注意 Calendar.DAY_OF_MONTH 返回1到31之间的月份

我建议使用时间戳,然后将结果从毫秒转换为天数,如下所示:

long oneDay = 24 * 60 * 60 * 1000;  // in milliseconds
long diff = day.getTime().getTime() - calCurr.getTime().getTime();
long numberOfDays = diff / oneDay;

然后你可以把它改成 String 具有 Long.toString(numberOfDays)

java.time文件,现代Java日期和时间API,提供了计算两个日期之间天数的方法。所以不要费心自己做这个计算。它容易出错。

    DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("dd-MM-uuuu H:mm");
    String inputDateString = "01-10-2018 23:59";
    LocalDate today = LocalDate.now(ZoneId.of("Pacific/Auckland"));
    LocalDate expiration = LocalDate.parse(inputDateString, dateFormatter);
    if (expiration.isAfter(today)) {
        String numberOfDays = "Days left: " + ChronoUnit.DAYS.between(today, expiration);
        System.out.println(numberOfDays);
    }

刚才运行这个片段(已经是9月13日在新西兰),我得到了以下输出:

如果不是太平洋/奥克兰,请用正确的时区代替。

LaVepe的答案已经很好地正确地解释了代码中的错误,所以我不再重复。

您使用的日期和时间类 Calendar 和 SimpleDateFormat 日历 日期格式 因为它给许多程序员带来的麻烦而臭名昭著。我建议您完全避免使用这些类并使用java.time文件相反。

问题:我能用吗java.time文件在Android上?

对, java.time 在较旧和较新的Android设备上运行良好。它至少需要Java 6

• 在java8及更高版本和更新的Android设备上(据Im所知,来自API级别26),现代API是内置的。
• 在Java6和Java7中,获取三个十的Backport,即新类的Backport(三个十用于JSR310;请参阅底部的链接)。
• 在(旧的)Android上使用Android版本的ThreeTen Backport。它叫3TENABP。并确保从导入日期和时间类 org.threeten.bp

链接

• Answer by LaVepe
• Oracle tutorial: Date Time 解释如何使用 java.time文件
• Java Specification Request (JSR) 310 ,在哪里 java.time文件
• ThreeTen Backport project 的后端口
• ThreeTenABP ,Android版Three Ten Backport
• Question: How to use ThreeTenABP in Android Project

试试这个方法

/**
         *  
         * @param token
         * @param date1 present date
         * @param date2 future date 
         * @return diff
         */
        public float dateDiff(String token,Date date1,Date date2){

            float diff=0;
            //different date might have different offset
            Calendar cal1=Calendar.getInstance(); 
            Calendar cal2=Calendar.getInstance();
            cal1.setTime(date1);          
            long ldate1 = date1.getTime() + cal1.get(Calendar.ZONE_OFFSET) + cal1.get(Calendar.DST_OFFSET);

            if(date2==null)
                cal2.setTime(new Date());
            else
                cal2.setTime(date2);
            long ldate2 = date2.getTime() + cal2.get(Calendar.ZONE_OFFSET) + cal2.get(Calendar.DST_OFFSET);

            // Use integer calculation, truncate the decimals
            int hr1   = (int)(ldate1/3600000); //60*60*1000
            int hr2   = (int)(ldate2/3600000);

            int days1 = hr1/24;
            int days2 = hr2/24;
            int dateDiff  = days2 - days1;
            int yearDiff  = cal2.get(Calendar.YEAR) - cal1.get(Calendar.YEAR); 
            float monthDiff = yearDiff * 12 + cal2.get(Calendar.MONTH) - cal1.get(Calendar.MONTH);
            System.out.println("monthDiff 1" +monthDiff);
            System.out.println(" days:  ;;;;222  "+dateDiff);
            float fbm = dateDiff ; 

            fbm = (float) MasterLibraryFunction.doubRound(fbm /30,2) ;

                if(token.equals("d"))
            {
                diff=dateDiff;
                System.out.println(" days:  ;;;;  "+dateDiff);
            }
            else if(token.equals("m"))
            {
                //diff= monthDiff;
                diff =fbm;
                System.out.println(" diff ---------->:  ;;;;  "+fbm);

            }

    /*******day wise diff *******/      


            return diff;
        }



/**
     * @category Decimal point round
     * @param  val
     * @param  places
     * @return Rounded Value to given place
     */
    public static double doubRound(double val, int places) {
        long factor = (long)Math.pow(10,places);
        val = val * factor;
        long tmp = Math.round(val);
        return (double)tmp / factor;
    }

public long daysTillExpire() {

    SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
    String dateInString = "01-10-2018 23:59";
    Date date = null;
    try {
        date = sdf.parse(dateInString);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    Calendar expiredCalendar = Calendar.getInstance();
    expiredCalendar.setTime(date);

    long msDiff = expiredCalendar.getTimeInMillis() - Calendar.getInstance().getTimeInMillis();
    long daysDiff = TimeUnit.MILLISECONDS.toDays(msDiff); 

    return daysDiff;
}

以上功能测试成功,请根据您的要求进行修改。