弹出窗口中的UIDatePicker随机不会第一次更新，而是每次都会更新

Question

我有一个弹出窗口中显示的UIDatePicker。当我旋转时，价值不会更新的时间有一半，然后每次都会更新。另一半，它在第一次和每次都更新 - 就像预期的一样。方案1：点击，选择时间，更新，值更新，再次更新，值再次更新...重复。场景2：点击，选择时间，更新，值不更新，再次更新，值更新，再次更新，值更新...重复。

起初，它每次都是第一次跳过更新，然后实施this answer's fix似乎有所帮助，直到我更多地使用它才看到它现在只有大约一半的时间有效。

@property (nonatomic, strong) UIViewController *datePickerController; 

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { 
    if (indexPath.row == kAddEditProductsTargetBatchTime) { 
     [self setupDatePickerWithIndexPath:indexPath]; 
    } 
} 

- (void)setupDatePickerWithIndexPath:(NSIndexPath *)indexPath { 
    CGRect cellFrame = [self.tableView rectForRowAtIndexPath:indexPath]; 
    CGRect popoverFrame = CGRectMake(cellFrame.size.width - 100.0f, cellFrame.origin.y, 50.0f, cellFrame.size.height); 

    CGSize dpSize = CGSizeMake(200, 180); 
    _datePickerController = [[UIViewController alloc] init]; 

    UIDatePicker *datePicker=[[UIDatePicker alloc]init]; 

    datePicker.frame = CGRectMake(0,0,dpSize.width, dpSize.height); 
    datePicker.datePickerMode = UIDatePickerModeCountDownTimer; 
    datePicker.countDownDuration = 0; 

    batchTarget *defaultCycleTarget = [cycleTargetRepository defaultCycleTarget:_product.cycleTargets]; //NSTimeInterval 

    if (indexPath.row == kAddEditProductsTargetBatchTime) { 
     NSDateComponents *dateComp = [NSDateComponents new]; 
     dateComp.hour = [NSNumberFormatter hoursComponent:defaultCycleTarget.targetBatchTime]; //NSTimeInterval 
     dateComp.minute = [NSNumberFormatter minutesComponent:defaultCycleTarget.targetBatchTime]; //NSTimeInterval 
     NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian]; 
     NSDate *pickerDate = [calendar dateFromComponents:dateComp]; 

     [datePicker setDate:pickerDate animated: YES]; 
     [datePicker addTarget:self action:@selector(batchTimeChanged:) forControlEvents:UIControlEventValueChanged]; 
    } 
    _datePickerController.view = datePicker; 

    _datePickerController.modalPresentationStyle = UIModalPresentationPopover; 
    _datePickerController.preferredContentSize = dpSize; 
    [self presentViewController:_datePickerController animated:YES completion:nil]; 
    _datePickerController.popoverPresentationController.sourceRect = popoverFrame; 
    _datePickerController.popoverPresentationController.sourceView = self.view; 
} 

//timeChanged doesn't even get fired off.. randomly && only on the first try 
- (void)timeChanged:(UIDatePicker *)sender { 
    batchTarget *defaultCycleTarget = [cycleTargetRepository defaultCycleTarget:_product.cycleTargets]; 
    if (defaultCycleTarget) { 
     defaultCycleTarget.targetBatchTime = sender.countDownDuration; 
    } else { 
     // If no defaultCycleTarget we need to initialize the data 
     batchTarget *newCycleTarget = [batchTarget new]; 
     newCycleTarget.targetBatchTime = sender.countDownDuration; 
     _product.cycleTargets = [NSArray arrayWithObject:newCycleTarget]; 
    } 
    [self.tableView reloadData]; 
} 

我基本上有same exact code in a different view using Swift并遇到同样的问题。

Answer 1

看起来像iOS缓冲区问题。

尝试更改runloop并使60秒的倍数。这个对我有用。

- (void) someMethodName 
{ 
    [self performSelector:@selector(sel:) withObject:datePicker afterDelay:0]; 
} 

- (void) sel:(UIDatePicker *)datePicker 
{ 
    datePicker.countDownDuration = 60; 
}