如何获取下一个和上一个星期的日期在Android

Question

public String getCurrentWeekDate() { 
    Calendar c = GregorianCalendar.getInstance(); 
    System.out.println("Current week = " + Calendar.DAY_OF_WEEK); 
    c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); 
    System.out.println("Current week = " + Calendar.DAY_OF_WEEK); 
    DateFormat df = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault()); 
    String startDate = "", endDate = ""; 
    startDate = df.format(c.getTime()); 
    c.add(Calendar.DATE, 6); 
    endDate = df.format(c.getTime()); 
    System.out.println("Start Date = " + startDate); 
    System.out.println("End Date = " + endDate); 

    return ""; 
} 

这是我的代码，我从中得到本周的日期在给定的时间格式，如2017-07-17至2017-07-23。

if (v.getId() == R.id.previousButtonView) { 
    getCurrentWeekDate(); 
} else if (v.getId() == R.id.nextButtonView) { 
    getCurrentWeekDate(); 
} 

这是我的代码，我有显示下周前一周日期请建议我如何增加和减少每周日我在android系统是新的。

Answer 1

对于下周calendar.add(Calendar.DAY_OF_WEEK, 1);

对于前一周calendar.add(Calendar.DAY_OF_WEEK, -1);

public void getCurrentWeekDate(int week) { 
    Calendar c = GregorianCalendar.getInstance(); 
    c.setFirstDayOfWeek(Calendar.MONDAY); 
    c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek()); 
    c.add(Calendar.DAY_OF_WEEK, week); 
    DateFormat df = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault()); 
    String startDate; 
    String endDate; 
    startDate = df.format(c.getTime()); 
    c.add(Calendar.DAY_OF_MONTH, 6); 
    endDate = df.format(c.getTime()); 
    System.out.println("Start Date = " + startDate); 
    System.out.println("End Date = " + endDate); 
} 

Answer 2

既然你已经找到本周的日期，所有你需要做的就是减去7天为前一周的日期，加上7天为下周的日期。

你可以通过下面的代码

int x = -7; 
Calendar cal = GregorianCalendar.getInstance(); 
cal.add(Calendar.DAY_OF_YEAR, x); 
Date sevenDaysAgo = cal.getTime(); 

所以，你的代码看起来像下面 -

public void getCurrentWeekDate(int week) { 
    Calendar c = GregorianCalendar.getInstance(); 
    System.out.println("Current week = " + Calendar.DAY_OF_WEEK); 
    c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); 
    System.out.println("Current week = " + Calendar.DAY_OF_WEEK); 
    DateFormat df = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault()); 
    String startDate; 
    String endDate; 
    startDate = df.format(c.getTime()); 

    // previous week calculation 
    Calendar previousWeekCalendar = c; 
    previousWeekCalendar.add(Calendar.DAY_OF_YEAR, -7); 
    startPreviousWeekDate = df.format(previousWeekCalendar.getTime()); 
    previousWeekCalendar.add(Calendar.DATE, 6); 
    endPreviousWeekDate = df.format(previousWeekCalendar.getTime()); 

    c.add(Calendar.DATE, 6); 
    //for previous week 
    //c.add(Calendar.DAY_OF_WEEK, -1); 
    //for next week 
    c.add(Calendar.DAY_OF_WEEK, week); 
    endDate = df.format(c.getTime()); 


    // Do next week calculation same as previous week. Just check what is the value of c before starting the calculation 
    System.out.println("Start Date = " + startDate); 
    System.out.println("End Date = " + endDate); 
    System.out.println("End Date = " + endDate); 

}