Question

我想获取给定星期数的开始和结束日期。我尝试了以下代码，但始终返回相同的日期（当前星期）

val c: Calendar = Calendar.getInstance()
val week = 39
 
c.set(Calendar.WEEK_OF_YEAR, week)
 
val firstDayOfWeek = c.firstDayOfWeek
c.set(Calendar.DAY_OF_WEEK,firstDayOfWeek)
startDate = SimpleDateFormat("yyyy-MM-dd",Locale.getDefault()).format(c.time).toString()
 
c.set(Calendar.DAY_OF_WEEK, firstDayOfWeek+6)
endDate = SimpleDateFormat("yyyy-MM-dd",Locale.getDefault()).format(c.time).toString()

Answer 1

我通过在使用前多拨c.time来解决它。这是工作代码：

val c: Calendar = Calendar.getInstance()//Locale.getDefault())
val week = 39
c.set(Calendar.WEEK_OF_YEAR, week)
val t = c.time;
val firstDay = c.firstDayOfWeek
c.set(Calendar.DAY_OF_WEEK,firstDay)
startDate = SimpleDateFormat("yyyy-MM-dd",Locale.getDefault()).format(c.time).toString()
c.set(Calendar.DAY_OF_WEEK,firstDay+6)
endDate = SimpleDateFormat("yyyy-MM-dd",Locale.getDefault()).format(c.time).toString()

无法理解其工作原理，请阅读此https://developer.android.com/reference/java/util/Calendar#field-manipulation

后尝试

Answer 2

您必须丢失某些东西或犯一些基本错误。以下是证明：

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault());
        int week = 39;

        Calendar c = Calendar.getInstance();
        c.set(Calendar.WEEK_OF_YEAR, week);

        int firstDayOfWeek = c.getFirstDayOfWeek();

        // Start date
        c.set(Calendar.DAY_OF_WEEK, firstDayOfWeek);
        String startDate = sdf.format(c.getTime());
        System.out.println(startDate);

        // End date
        c.set(Calendar.DAY_OF_WEEK, firstDayOfWeek + 6);
        String endDate = sdf.format(c.getTime());
        System.out.println(endDate);
    }
}

输出：

2020-09-21
2020-09-27

注意：：我不了解Kotlin，但不了解AFAIK，您也可以在Kotlin中运行Java代码。如果您想坚持使用Kotlin语法，希望您能够轻松将其转换为Kotlin语法。

从星期数获取星期开始和结束日期

2 个答案: