Android的比較日期時間

Question

我想比較兩個日期時間，但我無法讓它工作。

public void time() { 
     Calendar c11 = Calendar.getInstance(); 
     c11.add(Calendar.DAY_OF_YEAR, 0); 
     c11.set(Calendar.HOUR_OF_DAY, 9); 
     c11.set(Calendar.MINUTE, 0); 
     c11.set(Calendar.SECOND, 0); 

     Calendar c12 = Calendar.getInstance(); 
     c12.add(Calendar.DAY_OF_YEAR, 0); 
     c12.set(Calendar.HOUR_OF_DAY, 9); 
     c12.set(Calendar.MINUTE, 0); 
     c12.set(Calendar.SECOND, 0); 

     c11.getTime(); 
     c12.getTime(); 
     boolean k = c11.equals(c12); 
     if (k==true) 
     { 
      Toast.makeText(
       getContext(), 
       "Wow these two times are the same!", 
       Toast.LENGTH_LONG).show(); 
     } 
    } 
    } 

Answer 1

1. 2個時間值的毫秒是不同的，因此相等比較會返回false。

2. 爲什麼要在兩個日曆實例中添加0天？那什麼都不做。

Answer 2

public void onDateSelected(DateTime dateSelected) { 
    DateTime currentDateTime = new DateTime(); 

    try{ 
     /* If you want to compare only date from DateTime object then, 
      you can use "yyyy-MM-dd" format and split the string from T like: 
      dateSelected.toString().split("T") and use str1[0] to parse */ 

     SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ"); 

     String str1 = dateSelected.toString(); 
     Date selectedDate = formatter.parse(str1); 

     String str2 = currentDateTime.toString(); 
     Date currentDate = formatter.parse(str2); 

     if (selectedDate.compareTo(currentDate)<0) 
     { 
      System.out.println("current date is Greater than my selected date"); 
     } 

    }catch (ParseException e1){ 
     e1.printStackTrace(); 
    } 
}