Android 日历:到达未来的一天

Android Calendar: Get to the future day

我想为用户选择的特定日期设置警报，当我设置为当前日期的前一天时，它将它设置为过去的日期，我希望它设置为未来。

这是我的日历设置代码：

Calendar calendar = Calendar.getInstance();

calendar.set(Calendar.HOUR_OF_DAY, hour.getHour());

calendar.set(Calendar.MINUTE, 0);

calendar.set(Calendar.SECOND, 0);

calendar.set(Calendar.AM_PM, Calendar.AM);

calendar.set(Calendar.DAY_OF_WEEK, Calendar.Monday);

//future date

Calendar thatDay = Calendar.getInstance();

thatDay.set(Calendar.HOUR_OF_DAY, hour.getHour());

thatDay.set(Calendar.MINUTE, 0);

thatDay.set(Calendar.SECOND, 0);

thatDay.set(Calendar.AM_PM, Calendar.AM);

thatDay.set(Calendar.DAY_OF_WEEK, Calendar.Monday);



//current date

Calendar newDay = Calendar.getInstance();



long diff = thatDay.getTimeInMillis() - newDay.getTimeInMillis(); //result in millis



//result in days

long days = diff / (24 * 60 * 60 * 1000);

Calendar calendar = Calendar.getInstance();

calendar.set(Calendar.HOUR_OF_DAY, hour.getHour());

calendar.set(Calendar.MINUTE, 0);

calendar.set(Calendar.SECOND, 0);

calendar.set(Calendar.AM_PM, Calendar.AM);

calendar.add(Calendar.DATE, daysCount); // Add daysCount days to current date

假设今天是星期四，当我将日期设置为星期一时，我希望它设置为 4 天后，但它设置为 3 天前，到星期一

您可以使用以下"技术"：

• 计算当前日期与您想在未来设置为日历的日期之间的天数差，例如

  Calendar calendar = Calendar.getInstance();
  
  calendar.set(Calendar.HOUR_OF_DAY, hour.getHour());
  
  calendar.set(Calendar.MINUTE, 0);
  
  calendar.set(Calendar.SECOND, 0);
  
  calendar.set(Calendar.AM_PM, Calendar.AM);
  
  calendar.set(Calendar.DAY_OF_WEEK, Calendar.Monday);
  
  //future date
  
  Calendar thatDay = Calendar.getInstance();
  
  thatDay.set(Calendar.HOUR_OF_DAY, hour.getHour());
  
  thatDay.set(Calendar.MINUTE, 0);
  
  thatDay.set(Calendar.SECOND, 0);
  
  thatDay.set(Calendar.AM_PM, Calendar.AM);
  
  thatDay.set(Calendar.DAY_OF_WEEK, Calendar.Monday);
  
  
  
  //current date
  
  Calendar newDay = Calendar.getInstance();
  
  
  
  long diff = thatDay.getTimeInMillis() - newDay.getTimeInMillis(); //result in millis
  
  
  
  //result in days
  
  long days = diff / (24 * 60 * 60 * 1000);
  
  Calendar calendar = Calendar.getInstance();
  
  calendar.set(Calendar.HOUR_OF_DAY, hour.getHour());
  
  calendar.set(Calendar.MINUTE, 0);
  
  calendar.set(Calendar.SECOND, 0);
  
  calendar.set(Calendar.AM_PM, Calendar.AM);
  
  calendar.add(Calendar.DATE, daysCount); // Add daysCount days to current date

• 将步骤 1 中计算的天数添加到日历中，例如：

  Calendar calendar = Calendar.getInstance();
  
  calendar.set(Calendar.HOUR_OF_DAY, hour.getHour());
  
  calendar.set(Calendar.MINUTE, 0);
  
  calendar.set(Calendar.SECOND, 0);
  
  calendar.set(Calendar.AM_PM, Calendar.AM);
  
  calendar.set(Calendar.DAY_OF_WEEK, Calendar.Monday);
  
  //future date
  
  Calendar thatDay = Calendar.getInstance();
  
  thatDay.set(Calendar.HOUR_OF_DAY, hour.getHour());
  
  thatDay.set(Calendar.MINUTE, 0);
  
  thatDay.set(Calendar.SECOND, 0);
  
  thatDay.set(Calendar.AM_PM, Calendar.AM);
  
  thatDay.set(Calendar.DAY_OF_WEEK, Calendar.Monday);
  
  
  
  //current date
  
  Calendar newDay = Calendar.getInstance();
  
  
  
  long diff = thatDay.getTimeInMillis() - newDay.getTimeInMillis(); //result in millis
  
  
  
  //result in days
  
  long days = diff / (24 * 60 * 60 * 1000);
  
  Calendar calendar = Calendar.getInstance();
  
  calendar.set(Calendar.HOUR_OF_DAY, hour.getHour());
  
  calendar.set(Calendar.MINUTE, 0);
  
  calendar.set(Calendar.SECOND, 0);
  
  calendar.set(Calendar.AM_PM, Calendar.AM);
  
  calendar.add(Calendar.DATE, daysCount); // Add daysCount days to current date

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你应该add而不是set。添加后，Calendar 实例将正确地前进或减去(您也可以添加负数)。

通过设置属性之一，您可能必须处理所有回合和携带。

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