xcode UIAlertController 显示延迟
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UIAlertController showing with delay
提问by user3197643
I'm experiencing a problem with UIAlertController on my app now migrated to iOS8 with Date Picker inside.
我的应用程序上的 UIAlertController 出现问题，现在已迁移到 iOS8，内部带有日期选择器。
Below is the code.
下面是代码。
UIAlertController *AlertView = [UIAlertController alertControllerWithTitle:title message:nil preferredStyle:UIAlertControllerStyleActionSheet];
UIAlertAction *ok = [UIAlertAction actionWithTitle:@"Ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action)
{
[AlertView dismissViewControllerAnimated:YES completion:nil];
}];
UIAlertAction *set = [UIAlertAction actionWithTitle:NSLocalizedString(@"Set to today", nil) style:UIAlertActionStyleDefault handler:^(UIAlertAction *action)
{
[self set_to_today:nil];
[AlertView dismissViewControllerAnimated:YES completion:nil];
[self.tableView reloadData];
}];
UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action)
{
[AlertView dismissViewControllerAnimated:YES completion:nil];
}];
UIDatePicker *datePicker = [[[UIDatePicker alloc] init] autorelease];
datePicker.datePickerMode = UIDatePickerModeDate;
[datePicker setDate:data_appo];
[datePicker addTarget:self action:@selector(datePickerValueChanged:) forControlEvents:UIControlEventValueChanged];
[AlertView.view addSubview:datePicker];
[AlertView addAction:ok];
[AlertView addAction:set];
[AlertView addAction:cancel];
[self.view bringSubviewToFront:datePicker];
[self presentViewController:AlertView animated:YES completion:nil];
UIAlertController and Date Picker is shown when the user select a row from UITableViewController.
当用户从 UITableViewController 中选择一行时，会显示 UIAlertController 和日期选择器。
The problem is the following: first time the users select the row everything works fine...but if the user select "Cancel" and then select de tate again the UIAlertController takes 2-3 seconds to show up...this happens also in the simulator...
问题如下：第一次用户选择行时一切正常......但是如果用户选择“取消”然后再次选择细节，UIAlertController 需要 2-3 秒才能显示......这也会发生在模拟器...
I'm getting crazy....this makes my app have a bad user experience.
我快疯了……这让我的应用程序的用户体验很差。
Any help will be strongly appreciated Thanks
任何帮助将不胜感激谢谢
Alex
亚历克斯
回答by Tomusm
I was having the same issue with a UIAlertController presented by selecting a row from a UITableView. The first time everything worked fine, and then when the user triggered the alert again there was a few seconds delay before the alert was actually presented.
我在通过从 UITableView 中选择一行来呈现 UIAlertController 时遇到了同样的问题。第一次一切正常，然后当用户再次触发警报时，在实际显示警报之前有几秒钟的延迟。
As a workaround I used GCD:
作为一种解决方法，我使用了 GCD：
dispatch_async(dispatch_get_main_queue(), ^{
[self presentViewController:AlertView animated:YES completion:nil];
});
It is probably a bug since -(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPathis already executed on the main thread.
这可能是一个错误，因为-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath它已经在主线程上执行了。
I submitted a bug report to Apple: rdar://19285091
我向 Apple 提交了错误报告：rdar://19285091
回答by Mikrasya
DispatchQueue.main.async {
self.present(alertView, animated: true, completion:nil)
}
Swift 3.0 version. Alternatively, setting animated: false also solved my problem.
斯威夫特 3.0 版本。或者，设置 animation: false 也解决了我的问题。
