java - 获取直到午夜的毫秒数

Question

我正在创建一个我想在每晚午夜更新的 Android 小部件。我正在使用一个AlarmManager，我需要找出从当前时间到午夜还剩下多少毫秒。这是我的代码：

AlarmManager mAlarmManager = (AlarmManager)context.getSystemService(android.content.Context.ALARM_SERVICE);
mAlarmManager.set(AlarmManager.ELAPSED_REALTIME, millisecondsUntilMidnight, mSrvcPendingingIntent);

如何计算距离午夜还有多少毫秒？

先感谢您。

Answer 1

使用日历来计算它：

        Calendar c = Calendar.getInstance();
        c.add(Calendar.DAY_OF_MONTH, 1);
        c.set(Calendar.HOUR_OF_DAY, 0);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
        c.set(Calendar.MILLISECOND, 0);
        long howMany = (c.getTimeInMillis()-System.currentTimeMillis());

Answer 2

Answer 3

尝试以下操作：

Calendar c = Calendar.getInstance();
long now = c.getTimeInMillis();
c.add(Calendar.DATE, 1);
c.set(Calendar.HOUR_OF_DAY, 0);
c.set(Calendar.MINUTE, 0);
c.set(Calendar.SECOND, 0);
c.set(Calendar.MILLISECOND, 0);

long millisecondsUntilMidnight = c.getTimeInMillis() - now;

AlarmManager mAlarmManager = (AlarmManager)context.getSystemService(android.content.Context.ALARM_SERVICE);
mAlarmManager.set(AlarmManager.ELAPSED_REALTIME, millisecondsUntilMidnight, mSrvcPendingingIntent);

Answer 4

这行得通吗？

long MILLIS_IN_DAY = 86400000;

long currentTime = System.currentTimeInMillis();

long millisTillNow = currentTime % MILLIS_IN_DAY;

long millisecondsUntilMidnight = MILLIS_IN_DAY - millisTillNow;

Answer 5

您可以使用AlarmManager.RTC而不是AlarmManager.ELAPSED_REALTIME，只需将日历设置为您想要的时间：

// Create a calendar for midnight
Calendar todayMidnight = Calendar.getInstance();
todayMidnight.add(Calendar.DATE, 1);
todayMidnight.set(Calendar.HOUR_OF_DAY, 0);
todayMidnight.set(Calendar.MINUTE, 0);
todayMidnight.set(Calendar.SECOND, 0);

// Create an alarm going off at midnight
mAlarmManager.set(
   AlarmManager.RTC, 
   todayMidnight.getTimeInMillis(), 
   mSrvcPendingingIntent
);

Answer 6

使用以下方式，无需担心设置 DAY_OF_MONTH。

    long msInDay = 86400000;
    Calendar c = Calendar.getInstance();
    c.set(Calendar.HOUR_OF_DAY, 0);
    c.set(Calendar.MINUTE, 0);
    c.set(Calendar.SECOND, 0);
    c.set(Calendar.MILLISECOND, 0);

    System.out.print(msInDay - (System.currentTimeMillis() - c.getTimeInMillis()));