我有一个日期文本视图，其中包含形如2011.09.17的日期字符串。我仍然希望保留这个日期字符串，但也想为某些特定的日期添加一些更加用户友好的信息，比如今天或昨天。例如，如果今天是2011.09.17，我希望我的文本视图显示昨天的值而不是2011.09.16，并且显示今天的值而不是2011.09.17。
我已经成功实现了这个功能，但是用了很多if/else语句，代码很丑陋。如果我想添加新的规则，例如如果日期超过一年，我想放置类似于去年之类的字符串...我就必须再次添加很多不美观的逻辑。
我的问题是，有没有更好的方法来解决这个问题？是否有类似于设计模式的东西可以使用？建议采用哪种方法来实现这个功能？我相信许多人都遇到过这样的问题。
是否有比成千上万个if语句更好的方法？如果没有，那么无论如何感谢你，至少我不会再寻找更优秀的解决方案了。
如果有任何建议、代码片段等，将不胜感激。
谢谢
public class RelativeWeekday {
private final Calendar mCalendar;
public RelativeWeekday(Calendar calendar) {
mCalendar = calendar;
}
@Override
public String toString() {
Calendar today = Calendar.getInstance(Locale.getDefault());
int dayOfYear = mCalendar.get(Calendar.DAY_OF_YEAR);
if (Math.abs(dayOfYear - today.get(Calendar.DAY_OF_YEAR)) < 2) {
return getRelativeDay(today);
}
return getWeekDay();
}
private String getRelativeDay(Calendar today) {
return DateUtils.getRelativeTimeSpanString(
mCalendar.getTimeInMillis(),
today.getTimeInMillis(),
DateUtils.DAY_IN_MILLIS,
DateUtils.FORMAT_SHOW_WEEKDAY).toString();
}
private String getWeekDay() {
SimpleDateFormat dayFormat = new SimpleDateFormat("EEEE");
return dayFormat.format(mCalendar.getTimeInMillis());
}
}
我通常使用这个方便的Java库来进行相对时间格式化。 Prety Time Library
试试这个，我使用joda-datatime2.2.jar和java SimpleDateFormat实现了它。
import java.text.SimpleDateFormat;
import java.util.Date;
import org.joda.time.DateMidnight;
import org.joda.time.DateTime;
import org.joda.time.Days;
public class SmartDateTimeUtil {
private static String getHourMinuteString(Date date){
SimpleDateFormat hourMinuteFormat = new SimpleDateFormat(" h:m a");
return hourMinuteFormat.format(date);
}
private static String getDateString(Date date){
SimpleDateFormat dateStringFormat = new SimpleDateFormat("EEE',' MMM d y',' h:m a");
return dateStringFormat.format(date);
}
private static boolean isToday (DateTime dateTime) {
DateMidnight today = new DateMidnight();
return today.equals(dateTime.toDateMidnight());
}
private static boolean isYesterday (DateTime dateTime) {
DateMidnight yesterday = (new DateMidnight()).minusDays(1);
return yesterday.equals(dateTime.toDateMidnight());
}
private static boolean isTomorrow(DateTime dateTime){
DateMidnight tomorrow = (new DateMidnight()).plusDays(1);
return tomorrow.equals(dateTime.toDateMidnight());
}
private static String getDayString(Date date) {
SimpleDateFormat weekdayFormat = new SimpleDateFormat("EEE',' h:m a");
String s;
if (isToday(new DateTime(date)))
s = "Today";
else if (isYesterday(new DateTime(date)))
s = "Yesterday," + getHourMinuteString(date);
else if(isTomorrow(new DateTime(date)))
s = "Tomorrow," +getHourMinuteString(date);
else
s = weekdayFormat.format(date);
return s;
}
public static String getDateString_shortAndSmart(Date date) {
String s;
DateTime nowDT = new DateTime();
DateTime dateDT = new DateTime(date);
int days = Days.daysBetween(dateDT, nowDT).getDays();
if (isToday(new DateTime(date)))
s = "Today,"+getHourMinuteString(date);
else if (days < 7)
s = getDayString(date);
else
s = getDateString(date);
return s;
}
}
使用和测试Util类的简单示例：
import java.util.Calendar;
import java.util.Date;
public class SmartDateTimeUtilTest {
public static void main(String[] args) {
System.out.println("Date now:"+SmartDateTimeUtil.getDateString_shortAndSmart(new Date()));
System.out.println("Date 5 days before :"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDay(-5)));
System.out.println("Date 1 day before :"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDay(-1)));
System.out.println("Date last month:"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureMonth(-1)));
System.out.println("Date last year:"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDate(-1)));
System.out.println("Date 1 day after :"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDay(1)));
}
public static Date getFutureDate(int numberOfYears){
Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.add(Calendar.YEAR, numberOfYears);
return c.getTime();
}
public static Date getFutureMonth(int numberOfYears){
Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.add(Calendar.MONTH, numberOfYears);
return c.getTime();
}
public static Date getFutureDay(int numberOfYears){
Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.add(Calendar.DATE, numberOfYears);
return c.getTime();
}
}
getRelativeTimeSpanString 自API级别3开始添加
getRelativeTimeSpanString（long time， long now， long minResolution）
返回一个字符串，描述“time”相对于“now”的时间。
过去的时间跨度格式为“42分钟前”。未来的时间跨度格式为“在42分钟内”。 您可以在此处找到更多信息：
https://developer.android.com/reference/android/text/format/DateUtils
Calendar now = Calendar.getInstance();
return DateUtils.getRelativeTimeSpanString(time, now.getTimeInMillis(), DateUtils.DAY_IN_MILLIS);
在 Android 中，在 build.gradle 文件中使用 JodaTime 库：
compile 'net.danlew:android.joda:2.9.9'
public static String formateddate(String date) {
DateTime dateTime = DateTimeFormat.forPattern("dd-MMM-yyyy").parseDateTime(date);
DateTime today = new DateTime();
DateTime yesterday = today.minusDays(1);
DateTime twodaysago = today.minusDays(2);
DateTime tomorrow= today.minusDays(-1);
if (dateTime.toLocalDate().equals(today.toLocalDate())) {
return "Today ";
} else if (dateTime.toLocalDate().equals(yesterday.toLocalDate())) {
return "Yesterday ";
} else if (dateTime.toLocalDate().equals(twodaysago.toLocalDate())) {
return "2 days ago ";
} else if (dateTime.toLocalDate().equals(tomorrow.toLocalDate())) {
return "Tomorrow ";
} else {
return date;
}
}