问题
I have a UIDatePicker using UIDatePickerModeTime that I use in an iPhone app modally, works fine:
Using this same basic code for iPad, but putting the view in a UIPopoverController gives some pretty inconsistent results. My desired mode (UIDatePickerModeTime) plus the other three modes are shown below. Notice how 2 of them are not rendering at all, but instead have no content
UIDatePickerModeTime
UIDatePickerModeCountDownTimer
UIDatePickerModeDateAndTime
UIDatePickerModeDate
What could be causing the UIDatePickerModeTime and UIDatePickerModeDateAndTime modes to go haywire?
回答1:
Instantiating the UIDatePicker with CGRectZero was the culprit. Even though the code worked on iPhone, and I call sizeToFit explicitly on it to set the size, changing the CGRectZero to CGRectMake(0,0,320,160) was what got it to display. Go figure.
来源：https://stackoverflow.com/questions/4025367/uidatepicker-not-rendering-properly-for-certain-modes-in-uipopovercontroller