弹出窗口中的 UIDatePicker 随机不会第一次更新，但之后每次都会更新

Question

我有一个 UIDatePicker 显示在弹出窗口中。当我旋转时，有一半的时间值不会更新，然后每次都会更新。另一半，它第一次更新，之后每次更新——正如预期的那样。

场景 1：点击、选择时间、更新、值更新、再次更新、再次值更新……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，它每次第一次都跳过更新，然后实施this answer's fix 似乎有所帮助，直到我更多地使用它，发现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

似乎是 iOS 缓冲区问题。

尝试更改运行循环并设置为 60 秒的倍数。它对我有用。

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

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