java - 在android中获取我指定时间之前的时间

Question

我正在制作一个闹钟应用程序，它应该能够显示下一次闹钟之前的时间。我可以使用当前时间、小时:分钟:AM/PM 值以及星期几，例如星期二凌晨 3:15。我该如何计算这个？我感兴趣的只是像这样打印它:07h 35m。

我所做的就是尝试将其转换为日期，然后将其转换回毫秒，并在后面进行一些数学运算，但它不起作用，我不断得到错误的结果。

编辑:

我的问题是，我的时间是由自定义 View 设置的，例如星期二凌晨 3:15。我需要将其转换为最接近的 Date 对象。例如，当今天是星期二，凌晨 2:00 时，我将只编辑时间，但当今天是星期五时，我需要添加一些天数和时间。

Answer 1

试试这个:

    SimpleDateFormat format = new SimpleDateFormat("hh:mm a EEE", Locale.ENGLISH);
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(format.parse("3:15 AM Tue").getTime());

    Calendar now = Calendar.getInstance();
    Calendar target = Calendar.getInstance();

    if (calendar.get(Calendar.DAY_OF_WEEK) > now.get(Calendar.DAY_OF_WEEK)) {
        target.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY));
        target.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
        target.add(Calendar.DATE, calendar.get(Calendar.DAY_OF_WEEK) - now.get(Calendar.DAY_OF_WEEK));
    } else if (calendar.get(Calendar.DAY_OF_WEEK) < now.get(Calendar.DAY_OF_WEEK)) {
        target.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY));
        target.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
        target.add(Calendar.DATE, 7 - (now.get(Calendar.DAY_OF_WEEK) - calendar.get(Calendar.DAY_OF_WEEK)));
    } else {
        if (calendar.get(Calendar.HOUR_OF_DAY) > now.get(Calendar.HOUR_OF_DAY)) {
            target.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY));
            target.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
        } else if (calendar.get(Calendar.HOUR_OF_DAY) < now.get(Calendar.HOUR_OF_DAY)) {
            target.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY));
            target.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
            target.add(Calendar.DATE, 7);
        } else {
            if (calendar.get(Calendar.MINUTE) > now.get(Calendar.MINUTE)) {
                target.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY));
                target.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
            } else if (calendar.get(Calendar.MINUTE) < now.get(Calendar.MINUTE)) {
                target.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY));
                target.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
                target.add(Calendar.DATE, 7);
            } else {
                // target time is now!
            }
        }
    }

    long remainingTime = target.getTimeInMillis() - now.getTimeInMillis();
    final long hr = TimeUnit.MILLISECONDS.toHours(remainingTime);
    final long min = TimeUnit.MILLISECONDS.toMinutes(remainingTime - TimeUnit.HOURS.toMillis(hr));
    String result =  String.format("%02d:%02d", hr, min);