UIDatePicker in UIDatePickerModeCountDownTimer mod

问题:

How to get/set the hours and minutes via code from a UIDatePicker in UIDatePickerModeCountDownTimer mode?

The situation:

• I have an interface in that a user selects just hours and minutes. Then, he saves the information (so, I have to get the hours and minutes from UIDatePicker via code to save in a DB).

• When the user is editing the information saved previously, I want to start the interface with the saved hours/minutes (so, I have to set the UIDatePicker hours and minutes via code with values from DB).

How do I do that with the UIDatePicker in UIDatePickerModeCountDownTimer mode?

Thanks in advance.

回答1:

You have to use the countDownDuration property in UIDatePicker when the date picker mode is set to UIDatePickerModeCountDownTimer.

The countdown duration is in seconds, so you can calculate that from a NSDate as follows (to test it just drop it into the viewDidLoad of any UIViewController):

// Create a new date with the current time
NSDate *date = [NSDate new];
// Split up the date components
NSDateComponents *time = [[NSCalendar currentCalendar] 
                            components:NSHourCalendarUnit | NSMinuteCalendarUnit 
                            fromDate:date];
NSInteger seconds = ([time hour] * 60 * 60) + ([time minute] * 60);

UIDatePicker *picker = [UIDatePicker new];
[picker setDatePickerMode:UIDatePickerModeCountDownTimer];
[picker setCountDownDuration:seconds];
[[self view] addSubview:picker];

So if the current time is 17:28, the UIDatePicker will show "17 hours 28 mins". Simly replace the NSDate with the one you get from the DB and you should be sorted :)