UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:nil delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
alert.delegate = self;
datePicker = [[UIDatePicker alloc] init];
datePicker.datePickerMode = UIDatePickerModeDate;
[alert setValue:datePicker forKey:@"accessoryView"];//关键句
[alert show];
