Android Java 如果两次之间的时间错误

Question

我正在使用 JSON 文件来存储会议的多个条目。我正在尝试在 Java 的 Calendar 对象中获取使用 date.before 和 date.after 的当前事件。我当前的代码正在返回三个不同的事件，我不知道，我想知道有人对我尝试过的所有事情有任何建议。我将在下面附上 JSON 和代码。我还将附上代码放入控制台窗口的内容。

控制台日志

11-22 15:54:12.883 5797-5797/reloaded D/timetest:
    add event with name:Coffee Break
    time start: Tue Nov 22 15:30:00 GMT+00:00 18
    time end: Wed Nov 23 16:30:00 GMT+00:00 18
    time now: Wed Nov 23 15:45:00 GMT+00:00 18
11-22 15:54:12.885 5797-5797/reloaded D/timetest:
    add event with name:Panel Discussion
    time start: Tue Nov 22 16:30:00 GMT+00:00 18
    time end: Wed Nov 23 17:15:00 GMT+00:00 18
    time now: Wed Nov 23 15:45:00 GMT+00:00 18
11-22 15:54:12.888 5797-5797/reloaded D/timetest:
    add event with name:Turning Information into an Engaging Experience – The Design of Media Spaces
    time start: Tue Nov 22 17:15:00 GMT+00:00 18
    time end: Wed Nov 23 18:00:00 GMT+00:00 18
    time now: Wed Nov 23 15:45:00 GMT+00:00 18

JSON

{
      "eventid": "11",
      "roomid": "9",
      "type": "other",
      "name": "Coffee Break",
      "timestart": "15:30",
      "timeend": "16:30",
      "day": "1",
      "text": "Discover the Future Forum",
      "pic": "coffeecup.png",
      "speakerid": "1",
      "speaker": ""
    },
    {
      "eventid": "12",
      "roomid": "9",
      "type": "other",
      "name": "Panel Discussion",
      "timestart": "16:30",
      "timeend": "17:15",
      "day": "1",
      "text": "",
      "pic": "welcometalk.png",
      "speakerid": "1",
      "speaker": "fudged"
    },
    {
      "eventid": "13",
      "roomid": "9",
      "type": "lecture",
      "name": "Turning Information into an Engaging Experience – The Design of Media Spaces",
      "timestart": "17:15",
      "timeend": "18:00",
      "day": "1",
      "text": "fdsfsd",
      "pic": "p4.jpg",
      "speakerid": "6",
      "speaker": "test"
    },

Java

try {
    String string1 = "22/11/18 " + c.getString("timestart");
    Date time1 = new SimpleDateFormat("dd/MM/yyyy HH:mm").parse(string1);
    Calendar calendar1 = Calendar.getInstance();
    calendar1.setTime(time1);

    String string2 = "22/11/18 " + c.getString("timeend");
    Date time2 = new SimpleDateFormat("dd/MM/yyyy HH:mm").parse(string2);
    Calendar calendar2 = Calendar.getInstance();
    calendar2.setTime(time2);
    calendar2.add(Calendar.DATE, 1);

    String someRandomTime = "22/11/18 15:45";
    Date d = new SimpleDateFormat("dd/MM/yyyy HH:mm").parse(someRandomTime);
    Calendar calendar3 = Calendar.getInstance();
    calendar3.setTime(d);
    calendar3.add(Calendar.DATE, 1);

    Date now = calendar3.getTime();

    Date timestart = calendar1.getTime();
    Date timeend = calendar2.getTime();

    if ((now.after(timestart)) && (now.before(timeend))) {
        Log.d("timetest","add event with name:"+c.getString("name") + " time start: " + timestart+ " time end " + timeend + " time now " + now);
    }
}
catch (ParseException e) {
    e.printStackTrace();
}

Answer 1

就像我在 cmets 部分提到的：

您可以将时间转换为毫秒，然后检查当前时间是否大于事件的开始时间。如果是，您将返回数据。

---

像这样：

try {
    String string1 = "22/11/18 " + c.getString("timestart");
    Date time1 = new SimpleDateFormat("dd/MM/yyyy HH:mm").parse(string1);
    Calendar calendar1 = Calendar.getInstance();
    calendar1.setTime(time1);

    //Convert event time to milliseconds
    int timestart = calendar1.get(Calendar.MILLISECOND);

    //Get current time in milliseconds
    Calendar calendarCurrent = Calendar.getInstance();
    calendarCurrent.setTime(new Date());
    int now = calendar.get(Calendar.MILLISECOND);


    //Check if the event time is greater then the current time
    if (timestart > now) {
        Log.d("timetest - ",+"Event "+c.getString("name")+" already started");
    }else{
        Log.d("timetest - ",+"Event "+c.getString("name")+" has not started yet");
    }
 } catch (ParseException e) {
     e.printStackTrace();
}

---

重要提示：

我还建议将事件的日期和时间以毫秒为单位存储在您的数据库中，而不是对其进行硬编码。在我的回答中，我这样做是为了演示目的。

如果您将开始时间和结束时间存储为毫秒，您将能够确定距离活动开始的剩余时间，例如 this。

Answer 2

您应该使用 java.time 包中提供的新 Java 日期和时间 API。 旧的 Date 和 Calendar 类是 flawed 并且已过时。

如果您只处理时间，那么您可以使用LocalTime 类来查看某个时间是否介于另外两个时间之间：

// First, parse the times
DateTimeFormatter f = DateTimeFormatter.ofPattern("HH:mm");
LocalTime startTime = LocalTime.parse(c.getString("timestart"), f);
LocalTime endTime = LocalTime.parse(c.getString("timeend"), f);

// Then check if now is between those two times
LocalTime now = LocalTime.now();
if (now.isAfter(startTime) && now.isBefore(endTime)) {
    ...
}

如果活动尚未开始，则告诉人们活动何时开始：

if (now.isBefore(startTime)) {
    Duration d = Duration.between(now, startTime);
    System.out.println("Event starting in about " + d);
}
else if (now.isBefore(endTime)) {
    System.out.println("Event is now going on");
}
else {
    System.out.println("Event has passed");
}

---

注意：我假设事件不会在每天的指定时间重复，因此您可能会考虑不仅存储时间，还存储日期。您可以将时间戳存储为整数，但2018-11-23T11:57:03+01:00 等格式也被广泛使用。然后，您可以使用 DateTimeFormatter 类轻松解析它们。